WO2007135581A2 - A device for and a method of processing audio data - Google Patents

A device for and a method of processing audio data Download PDF

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Publication number
WO2007135581A2
WO2007135581A2 PCT/IB2007/051626 IB2007051626W WO2007135581A2 WO 2007135581 A2 WO2007135581 A2 WO 2007135581A2 IB 2007051626 W IB2007051626 W IB 2007051626W WO 2007135581 A2 WO2007135581 A2 WO 2007135581A2
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WO
WIPO (PCT)
Prior art keywords
speakers
audio
microphone
audio data
loudspeaker
Prior art date
Application number
PCT/IB2007/051626
Other languages
French (fr)
Other versions
WO2007135581A3 (en
Inventor
Christophe M. Macours
Original Assignee
Koninklijke Philips Electronics N.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2007135581A2 publication Critical patent/WO2007135581A2/en
Publication of WO2007135581A3 publication Critical patent/WO2007135581A3/en

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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04RLOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R5/00Stereophonic arrangements
    • H04R5/02Spatial or constructional arrangements of loudspeakers
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04SSTEREOPHONIC SYSTEMS 
    • H04S7/00Indicating arrangements; Control arrangements, e.g. balance control
    • H04S7/30Control circuits for electronic adaptation of the sound field
    • H04S7/301Automatic calibration of stereophonic sound system, e.g. with test microphone
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04RLOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2205/00Details of stereophonic arrangements covered by H04R5/00 but not provided for in any of its subgroups
    • H04R2205/024Positioning of loudspeaker enclosures for spatial sound reproduction
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04SSTEREOPHONIC SYSTEMS 
    • H04S3/00Systems employing more than two channels, e.g. quadraphonic

Definitions

  • the invention relates to a device for processing audio data. Beyond this, the invention relates to a method of processing audio data. Moreover, the invention relates to a program element. Furthermore, the invention relates to a computer-readable medium.
  • Audio playback devices become more and more important. Particularly, an increasing number of users buy audio surround systems comprising multiple loudspeakers. US 2005/0254662 Al discloses automatic calibration of an acoustic system.
  • the acoustic system may include a source A/V device, calibration computing device, and multiple rendering devices.
  • the calibration system may include a calibration component attached to each rendering device and a source calibration module.
  • the calibration component on each rendering device includes a microphone.
  • the source calibration module includes distance and optional angle calculation tools for automatically determining a distance between the rendering device and a specified reference point upon return of the test signal from the calibration component.
  • WO 2005/076912 A2 discloses a network including an audio signal producing device, a content distributor communicatively coupled to the audio signal producing device, a router, a network communication medium communicatively coupling the content distributor and the router, and a plurality of addressable loudspeakers communicatively coupled to the network communication medium, wherein each of the addressable loudspeakers are configured to function as a network peripheral in the home network.
  • a device for processing audio data a method of processing audio data, a program element and a computer-readable medium according to the independent claims are provided.
  • a device for processing audio data comprising at least one microphone (particularly a plurality of microphones) each adapted to detect audio data, a plurality of speakers each adapted to emit acoustic waves, wherein at least a part of (for instance each of) the plurality of speakers is provided (particularly equipped) with an assigned one of the at least one microphone, a calculation unit adapted to calculate acoustical transfer functions between the plurality of speakers based on the audio data detected by the at least one microphone, and a determining unit adapted to determine orientation information indicative of the relative orientation of the plurality of speakers based on the calculated acoustical transfer functions.
  • a method of processing audio data comprises detecting audio data using at least one microphone (particularly a plurality of microphones), emitting acoustic waves using a plurality of speakers, wherein at least a part of (for instance each of) the plurality of speakers is provided (particularly equipped with an assigned one of the at least one microphone, calculating acoustical transfer functions between the plurality of speakers based on the audio data detected by the at least one microphone, and determining orientation information indicative of the relative orientation of the plurality of speakers based on the calculated acoustical transfer functions.
  • a computer- readable medium in which a computer program of processing audio data is stored which, when being executed by a processor, is adapted to control or carry out a method having the above mentioned features.
  • a program element of processing audio data is provided, which program element, when being executed by a processor, is adapted to control or carry out a method having the above mentioned features.
  • Data processing for orientation estimation purposes which may be performed according to embodiments of the invention can be realized by a computer program, that is by software, or by using one or more special electronic optimization circuits, that is in hardware, or in hybrid form, that is by means of software components and hardware components.
  • an audio processing and/or playback system may be provided in which a configuration of a plurality of speakers (for instance loudspeakers or other reproduction apparatuses) may be determined automatically based on an evaluation of the audio emission and audio absorption properties of the speakers and assigned microphones. If necessary, the configuration of the speakers may be adjusted (for instance electronically and/or mechanically) so as to improve the audio playback performance of the multi-speaker apparatus.
  • each loudspeaker may emit (sequentially or simultaneously with the other loudspeakers) an audio signal (for instance a normal useful audio data signal or a signal specifically adapted for configuring) which may be detected by the microphones assigned (particularly located directly next to) to the other loudspeakers.
  • an audio signal for instance a normal useful audio data signal or a signal specifically adapted for configuring
  • the system may then adjust the playback characteristics of the speakers so as to improve the audio performance.
  • This may include adjusting parameters like audio amplitude, frequency distribution, filter characteristics, addition of special effects like reverberation, etc. It may also include modifying the geometrical arrangement of the loudspeakers, for instance changing the spatial orientation of the loudspeakers (for instance using an electromotor installed in each of the loudspeakers).
  • the audio playback quality may be improved particularly at a special spatial area or point (which may be user-defined or which may be the position at which a listener is currently located or which can be a center of gravity of the loudspeakers).
  • a user- friendly system may be provided which allows to automatically configuring the loudspeaker system in an appropriate manner even in a scenario in which a user has installed the loudspeakers in an incorrect manner.
  • Embodiments of the invention may take into account orientation properties of loudspeakers (having, in reality, directivity instead of being purely omni-directional). Thus, improper orientation may be compensated and it may thus be ensured that the loudspeaker points into the direction of a listener. Particularly, by considering transfer functions of an audio system, a frequency-amplitude characteristic may be taken into account for correcting the audio system properties.
  • each of the speakers has an assigned microphone.
  • a surround sound system may be provided comprising at least two loudspeakers, each equipped with a (closely positioned) microphone.
  • the surround sound system may further comprise a unit for measuring acoustical transfer functions between all speakers.
  • a unit for determining the orientation of the speakers based on the transfer functions may be foreseen.
  • an audio signal to be rendered by the speakers may be corrected based on the orientation information.
  • exemplary embodiments of the invention may not only have the capability that loudspeakers equipped with a microphone can automatically provide loudspeaker and/or room acoustics correction, but also the orientation of the loudspeakers may be taken into account.
  • exemplary embodiments of the invention do not have to assume the loudspeaker to be omni-directional and may provide specific means to correct its (possibly) wrong orientation with respect to a listening position.
  • automatic acoustic compensation in surround sound systems may be made possible.
  • a method for automatically correcting a wrong orientation of the loudspeakers in a home theatre (for instance in a 5.1 system, denoting a stereo format utilizing three primary channels (left, center, right), two surround channels (left surround, right surround) and an LFE channel, which is the ".1" channel because it uses approximately one-tenth of the bandwidth of a full- frequency channel) system based on the normalization of high frequency energy level contained in cross loudspeaker transfer functions may be made possible.
  • an automated home theatre calibration system may be provided to improve a configuration of a loudspeaker setup, particularly with regard to orientation. It may be advantageous that automatic home theatre calibration systems have a room correction feature. An issue is to compensate the acoustics of the loudspeakers in the listening room in order to get an improved or optimal ("flat") response at the listening position. To achieve this, it is conventionally possible to place a microphone at the listener position.
  • level correction compensation of the level (amplitude) differences between the different loudspeakers
  • delay correction ensures all loudspeaker signals arrive simultaneously at the listener position
  • low frequency room acoustics correction compensation of low frequency loudspeaker response and of the room (anti-)resonances and modes
  • high frequency room acoustics correction compensation of the high frequency loudspeaker response, of the room response and of the wrong orientation of the loudspeaker boxes.
  • a specific accessory for instance a microphone
  • exemplary embodiments of the invention are based on the recognition that the following reasoning holds: what parts of the possible improvements listed above would be possible if each loudspeaker box would be equipped with one microphone, without having a microphone at the listener position. Actually, it is not only possible to compute the geometrical configuration of the loudspeakers (by means of delay calculations). But it is also desirable to compensate for the wrong orientation of the loudspeaker boxes and simultaneously perform a high frequency room acoustics correction.
  • a system for automatically correcting a possibly wrong orientation of two, three, four, five, six, seven or more loudspeakers in a home theatre (for instance in a 5.1) system may be made possible by normalizing particularly high frequency energy level contained in the loudspeaker transfer functions.
  • the transfer function having the most energy at high frequencies may be considered as a reference.
  • transfer function may describe the transfer characteristics of a system or equipment. It may relate to the relationship between an input and an output of the system or equipment in terms of the transfer characteristics.
  • acoustical transfer function between loudspeakers/microphones may relate to properties of an acoustical transfer in an acoustic field between the loudspeakers (including the microphones connected thereto), determinable on the basis of electric signals derived from the detection of acoustical audio signals.
  • the transfer function may relate to the process by which an audio source wave passes through the space and is detected elsewhere. More particularly, a transfer function may be indicative of the transformation encountered by sound when passing from a source (like a loudspeaker) to a destination (like a microphone or a listener).
  • the transfer function may be amplitude versus frequency curve indicative of the sound characteristic of the audio system. For instance, when a "white" audio signal is emitted by a loudspeaker and detected by a microphone, the characteristic of the loudspeaker-microphone system may transfer the white audio signal into a frequency-amplitude curve. In an audio system comprising two microphones ands two loudspeakers, four transfer functions may be measured (microphone 1 -loudspeaker 1, microphone 1 -loudspeaker 2, microphone 2-loudspeaker 1, microphone 2- loudspeaker 2).
  • a loudspeaker box has a frequency dependent directivity characteristic.
  • a loudspeaker driver may act as a pure piston and the radiated sound field may be omni-directional.
  • the loudspeaker becomes more directive because the loudspeaker driver diameter becomes large relative to the wavelength. Therefore, a bad loudspeaker orientation can strongly effect the reproduction particularly of high frequencies.
  • Another aspect of bad loudspeaker orientation in a listening room is that if a loudspeaker box is pointing towards the wall, the wall may reflect a significant amount of energy back to the listening area. Because walls have a rather absorbent behavior, these reflected waves will also experience a low pass filtering that will also affect the overall frequency balance.
  • Exemplary fields of application of the embodiments of the invention are sound reproduction systems equipped with multiple (for instance at least two) loudspeakers, such as stereo (for instance portable) systems, and home theatre systems (for instance 5.1, 7.1, etc.).
  • stereo for instance portable
  • home theatre systems for instance 5.1, 7.1, etc.
  • the calculation unit may be adapted to calculate acoustical transfer functions between each pair of the plurality of speakers based on the audio data detected by the plurality of microphones.
  • one of the loudspeakers may emit an acoustical (test) signal, which acoustical (test) signal may be detected by all microphones assigned to the other loudspeakers. Transfer functions may be derived from this information.
  • the next loudspeaker may emit an audio signal and the microphones assigned to the remaining loudspeakers detect the corresponding audio signals.
  • all loudspeakers serve sequentially as an audio source and the microphones detect the corresponding audio signals as a basis for deriving the acoustical transfer functions. This procedure allows deriving all information necessary to analyze the systems. If desired, correction instructions may be provided so as to correct the orientation or acoustical emission properties of the loudspeakers.
  • the determining unit may be adapted to determine the orientation information indicative of the spatial positions and/or of the audio emission direction of the plurality of speakers. From the calculated acoustical transfer functions, applying basic mathematical procedures, the orientations and positions of the loudspeakers may be determined (for instance by evaluating intensities, applying damping models, analyzing delays, analyzing correlations between different signals, evaluating frequency information, considering directivity characteristics, evaluating propagation times in combination with propagation velocities, etc.). This orientation and position information may serve as a basis for correcting the setup of the speakers. At least a part of the plurality of speakers and the assigned one of the plurality of the microphones may be accommodated in a separate casing.
  • a plurality of modules or separate entities may be provided, wherein each microphone and the corresponding loudspeaker may be provided in a separate housing.
  • a correction unit may be provided and may be adapted to correct an audio playback characteristic of at least a part of the plurality of speakers based on the determined orientation information. Therefore, after having analyzed the proper audio emission properties of the speakers, the correction unit may adjust the audio playback characteristics of the speakers so as to improve the audio performance. For instance, the audio playback characteristics may be improved or even optimized for a predetermined listening position.
  • This listening position may be a user-defined position (for instance defined by a user of the sound system via an user interface), a geometrical center of the plurality of speakers (which may be calculated based on the knowledge at which positions the loudspeakers are positioned), or a position defined with respect to a given component of an audio system (for instance improving the sound quality in front of a television where a user is usually sitting when using the sound system).
  • a user-defined position for instance defined by a user of the sound system via an user interface
  • a geometrical center of the plurality of speakers which may be calculated based on the knowledge at which positions the loudspeakers are positioned
  • a position defined with respect to a given component of an audio system for instance improving the sound quality in front of a television where a user is usually sitting when using the sound system.
  • the adjusted audio playback characteristic may comprise an amplitude of the audio playback of an individual one of the speakers, of a part of the speakers or of all speakers, a frequency filtering characteristics (for instance the definition of cut-off frequencies or frequency bands), and an equalizer characteristic. These are only examples and may be substituted by or combined with any other audio playback characteristics.
  • the device may further comprise a correction unit that is adapted to correct the orientation of at least a part of the plurality of speakers based on the determined orientation information.
  • the speakers may also be provided to be movable (for instance adapted for a translational movement and/or for a rotational movement).
  • an electric motor may be provided, or the devices may simply be foreseen to be movable by a user. In the latter case, the user may be provided or guided by the device with an instruction as to how to modify a position and/or an orientation of one of the speakers to improve playback quality.
  • the calculation unit may be adapted to calculate the acoustical transfer functions between the plurality of speakers based on components of the audio data which components exceed a predetermined frequency threshold (of, for instance, several kHz).
  • a predetermined frequency threshold of, for instance, several kHz.
  • high frequencies may be particularly suitable to be analyzed in accordance with exemplary embodiments of the invention, since directivity of a loudspeaker is usually higher at high frequencies than at low frequencies.
  • a loudspeaker is essentially omnidirectional at low frequencies and shows directional behavior at high frequencies. Therefore, an evaluation in the high frequency domain may derive more meaningful results with regard to orientation.
  • Such a frequency threshold or transition frequency may be in the range of 500 Hz to 20 kHz, particularly in the range of 1 kHz to 5 kHz, more particularly in the range of 2 kHz to 4 kHz.
  • this frequency value at which a transition between an omni-directional behavior and a directive behavior occurs, is usually smaller, the larger the loudspeaker is. More generally, the value may be dependent on the size of the loudspeaker and consequently dependent on the size of an acoustical cone emitted by the loudspeaker.
  • the technical definition of the so-called "piston range of a cone loudspeaker” will be given.
  • the piston range, where a loudspeaker cone is considered as being omnidirectional, is technically defined by:
  • the way the loudspeaker is mounted may have an influence on the frequency value.
  • the device for processing audio data may be realized as at least one of the group consisting of an audio surround system, a stereo audio system, a mobile phone, a headset, a hearing aid, a hands free system, a television device, a video recorder, a monitor, a gaming device, a laptop, an audio player, a DVD player, a CD player, a hard disk-based media player, an internet radio device, a public entertainment device, a portable audio player, an MP3 player, a hi-fi system, a vehicle entertainment device, a car entertainment device, a medical communication system, a body-worn device, a speech communication device, a home cinema system, and a music hall system.
  • system primarily intends to improve the quality of sound or audio data
  • system for a combination of audio data and visual data
  • an embodiment of the invention may be implemented in audiovisual applications like a portable video player in which multiple speakers are used.
  • FIG. 1 shows an audio processing system according to an exemplary embodiment of the invention.
  • Figs. 2A and 2B shows an audio playback system in two different configurations according to exemplary embodiments of the invention.
  • Figs. 3 A and 3B illustrates a method of calibrating an audio processing system according to an exemplary embodiment of the invention.
  • Fig. 4 shows a flow diagram illustrating a method of processing audio data according to an exemplary embodiment of the invention.
  • the audio processing system 100 comprises a first microphone 101, a second microphone 102, a third microphone 103 and a fourth microphone 104.
  • the number of microphones may be larger or smaller than four, particularly may be larger than or equal to two.
  • Each of the microphones 101 to 104 is adapted to detect audio data emitted by anyone of a plurality of loudspeakers, namely a first loudspeaker 105, a second loudspeaker 106, a third loudspeaker 107 and a fourth loudspeaker 108.
  • a first housing 109 is provided in which the first microphone 101 and the first loudspeaker 105 are accommodated or integrated.
  • the second microphone 102 and the second loudspeaker 106 are embedded in a second housing 110.
  • the third microphone 103 and the third loudspeaker 107 are provided within a third housing 111.
  • a fourth housing 112 accommodates the fourth microphone 104 and the fourth speaker 108. Therefore, each of the microphones 101 to 104 has an assigned speaker 105 to 108, and these pairs are located directly neighbored or adjacent to one another.
  • the loudspeakers 105 to 108 are each adapted to emit acoustic waves and are each equipped with the corresponding microphone 101 to 104.
  • the audio system 100 is used for reproducing audio content and may serve as an audio surround system. However, the system 100 also has an automatic loudspeaker orientation configuration feature that will be explained in the following in more detail. With respect to the actual audio playback functionality of a surround system, no further details will be explained in the following.
  • each of the microphones 101 to 104 is electrically coupled to a calculation unit 113 so as to provide detected audio data 114 to 117 to the calculation unit 113.
  • the calculation unit 113 is adapted to calculate acoustical transfer functions between the plurality of speakers 105 to 108 based on the audio data 114 to 117 detected by the plurality of microphones 101 to 104.
  • the calculation unit 113 may calculate all acoustical transfer functions indicative of the acoustical properties of the system and indicative of the present orientation of the speakers 105 to 108 with respect to one another.
  • the determined acoustical transfer functions 118 are supplied to a determining unit 119 adapted to determine orientation information indicative of the relative orientation of the plurality of speakers 105 to 108 based on the calculated acoustical transfer functions 118. Therefore, the determining unit 119 determines the orientation (that is to say the spatial positions and/or the directions) of the speakers 105 to 108 so as to determine whether there is a need to modify the configuration of the loudspeakers arrangement to improve playback quality.
  • Corresponding orientation information 120 may be supplied to a correction unit 121 adapted to correct an audio playback characteristic of one or more of the loudspeakers 105 to 108 based on the determined orientation information 120.
  • control signals 122 can, if needed, be provided to the corresponding loudspeakers 105 to 108 to improve the audio performance.
  • the correction unit 121 may calculate the control parameters 122 in such a manner that an audio quality is improved at a predetermined listening position (for instance a position at which a listener is presently or usually located).
  • a user may input such a position to the system 100 via a user interface device 123.
  • Such an I/O device may include a graphical user interface (GUI) having an LCD, a plasma device, or a cathode ray tube.
  • input elements can be provided at the user interface 123 like a keypad, a joystick, buttons, a trackball, or even a microphone of a voice recognition system.
  • the control parameters 122 may alter amplitude of any signal to be reproduced by one of the loudspeakers 105 to 108, or may alter a frequency behavior, or may alter equalizer characteristics, or a spatial position of the microphones 105 to 108. Therefore, if needed, one or more of the loudspeakers 105 to 108 may be mechanically turned or shifted.
  • Fig. 2 shows a typical home theatre system setup in an ideal configuration 200 and in a non-ideal configuration 250.
  • Loudspeakers 105 to 108 are shown which are distributed around a human listener 201. Furthermore, a television 202 is shown which may also comprise one or more loudspeakers, wherein such a "center speaker” is assumed to be at the same position as the TV 202. In the "ideal" configuration 200 as shown in Fig. 2A, all loudspeaker boxes
  • the loudspeaker boxes 105 to 108 point towards the listener 201. But in many cases, as for instance shown in Fig. 2B for non-ideal configuration 250, the loudspeaker boxes 105 to 108 do not have an optimum orientation and will be pointing outside a listening area 203.
  • all loudspeakers 105 to 108, 202 are equipped with one omni-directional microphone (101 to 104, 204). This enables the measurement of the acoustical transfer functions between all loudspeakers 105 to 108, 202, the so-called "cross loudspeaker transfer functions". It is possible to make use of these transfer functions to get an idea of the orientation of the loudspeaker boxes 105 to 108, 202 with respect to the listener 201 and to provide the necessary corrections.
  • Fig. 3 shows two examples of cross loudspeaker transfer function measurements.
  • a first scenario 300 the loudspeaker box 1 is properly oriented.
  • a second scenario 350 the loudspeaker 4 is wrongly oriented.
  • the transfer functions between loudspeaker 1 and the others are measured. This may give an idea on the directivity of loudspeaker box 1. Because the directivity of a loudspeaker driver increases with frequency, a comparison of the high frequency content of the transfer functions can provide an idea of orientation of loudspeaker 1. Because the positions of the loudspeaker boxes can be computed, it can be possible, by interpolation, to estimate the high frequency energy level reaching the center of the listening area 203, where the listener 201 is assumed to be sitting. In the second scenario 350 as shown in Fig. 3B, it is the directivity of loudspeaker 4 that is measured.
  • the other loudspeakers will get much less high frequency energy than in the first scenario 300, which indicates that loudspeaker 4 is most likely wrongly oriented.
  • a high frequency boost filter to be applied to loudspeaker 4 can be derived.
  • FIG. 4 a block diagram 400 will be explained illustrating a method of processing audio data according to an exemplary embodiment of the invention. Such a method may work according to the following process:
  • the loudspeaker positions are computed (for instance by evaluating intensities, applying damping models, analyzing delays, analyzing correlations between different signals, evaluating frequency information, considering directivity characteristics, evaluating propagation times in combination with propagation velocities, etc.), see block 420.
  • the listening position is user-defined or assumed to be the geometrical center of the area enclosed by the loudspeakers, or assumed to be in front of the TV set, see block 430.
  • the high frequency energy level radiated in the direction of the listening position is computed by interpolating the high frequency content of the different cross loudspeaker measurements. Because of the oval shape of the loudspeaker directivity, the interpolation may be non-linear, see block 440.
  • the high frequency energy levels of all loudspeakers are normalized to the highest one.
  • the high frequency energy radiated towards the listening position is made equal for all loudspeakers, and preferably equal to the highest high frequency energy level value, see block 450.

Abstract

A device (100) for processing audio data, wherein the device (100) comprises a plurality of microphones (101 to 104) each adapted to detect audio data (114 to 117), a plurality of speakers (105 to 108) each adapted to emit acoustic waves and each equipped with an assigned one of the plurality of microphones (101 to 104), a calculation unit (113) adapted to calculate acoustical transfer functions (118) between the plurality of speakers (105 to 108) based on the audio data (114 to 117) detected by the plurality of microphones (101 to 104), and a determining unit (119) adapted to determine orientation information (120) indicative of the relative orientation of the plurality of speakers (105 to 108) based on the calculated acoustical transfer functions (120).

Description

A device for and a method of processing audio data
FIELD OF THE INVENTION
The invention relates to a device for processing audio data. Beyond this, the invention relates to a method of processing audio data. Moreover, the invention relates to a program element. Furthermore, the invention relates to a computer-readable medium.
BACKGROUND OF THE INVENTION
Audio playback devices become more and more important. Particularly, an increasing number of users buy audio surround systems comprising multiple loudspeakers. US 2005/0254662 Al discloses automatic calibration of an acoustic system.
The acoustic system may include a source A/V device, calibration computing device, and multiple rendering devices. The calibration system may include a calibration component attached to each rendering device and a source calibration module. The calibration component on each rendering device includes a microphone. The source calibration module includes distance and optional angle calculation tools for automatically determining a distance between the rendering device and a specified reference point upon return of the test signal from the calibration component.
WO 2005/076912 A2 discloses a network including an audio signal producing device, a content distributor communicatively coupled to the audio signal producing device, a router, a network communication medium communicatively coupling the content distributor and the router, and a plurality of addressable loudspeakers communicatively coupled to the network communication medium, wherein each of the addressable loudspeakers are configured to function as a network peripheral in the home network.
However, conventional audio systems comprising multiple loudspeakers may be difficult to install, since many consumers are not familiar with the mounting of complex audio systems.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the invention to provide a user- friendly audio system. In order to achieve the object defined above, a device for processing audio data, a method of processing audio data, a program element and a computer-readable medium according to the independent claims are provided.
According to an exemplary embodiment of the invention, a device for processing audio data is provided, wherein the device comprises at least one microphone (particularly a plurality of microphones) each adapted to detect audio data, a plurality of speakers each adapted to emit acoustic waves, wherein at least a part of (for instance each of) the plurality of speakers is provided (particularly equipped) with an assigned one of the at least one microphone, a calculation unit adapted to calculate acoustical transfer functions between the plurality of speakers based on the audio data detected by the at least one microphone, and a determining unit adapted to determine orientation information indicative of the relative orientation of the plurality of speakers based on the calculated acoustical transfer functions.
According to another exemplary embodiment of the invention, a method of processing audio data is provided, wherein the method comprises detecting audio data using at least one microphone (particularly a plurality of microphones), emitting acoustic waves using a plurality of speakers, wherein at least a part of (for instance each of) the plurality of speakers is provided (particularly equipped with an assigned one of the at least one microphone, calculating acoustical transfer functions between the plurality of speakers based on the audio data detected by the at least one microphone, and determining orientation information indicative of the relative orientation of the plurality of speakers based on the calculated acoustical transfer functions.
According to yet another exemplary embodiment of the invention, a computer- readable medium is provided, in which a computer program of processing audio data is stored which, when being executed by a processor, is adapted to control or carry out a method having the above mentioned features.
According to still another exemplary embodiment of the invention, a program element of processing audio data is provided, which program element, when being executed by a processor, is adapted to control or carry out a method having the above mentioned features.
Data processing for orientation estimation purposes which may be performed according to embodiments of the invention can be realized by a computer program, that is by software, or by using one or more special electronic optimization circuits, that is in hardware, or in hybrid form, that is by means of software components and hardware components. According to an exemplary embodiment of the invention, an audio processing and/or playback system may be provided in which a configuration of a plurality of speakers (for instance loudspeakers or other reproduction apparatuses) may be determined automatically based on an evaluation of the audio emission and audio absorption properties of the speakers and assigned microphones. If necessary, the configuration of the speakers may be adjusted (for instance electronically and/or mechanically) so as to improve the audio playback performance of the multi-speaker apparatus.
In a system like an audio surround system in which a plurality of loudspeakers have to be mounted and adjusted, it may be difficult for a user to configure this system in an optimum manner with regard to loudspeaker position and orientation, since a user is in many cases not an expert. In accordance with an exemplary embodiment of the invention, when a user has installed such a system, each loudspeaker may emit (sequentially or simultaneously with the other loudspeakers) an audio signal (for instance a normal useful audio data signal or a signal specifically adapted for configuring) which may be detected by the microphones assigned (particularly located directly next to) to the other loudspeakers. By taking this measure, the acoustical transfer functions of the loudspeaker/microphone systems may be detected in a pair wise manner.
By evaluating this information, it is possible to calculate back the relative orientations and/or relative positions of the loudspeakers. With this information, the system may then adjust the playback characteristics of the speakers so as to improve the audio performance. This may include adjusting parameters like audio amplitude, frequency distribution, filter characteristics, addition of special effects like reverberation, etc. It may also include modifying the geometrical arrangement of the loudspeakers, for instance changing the spatial orientation of the loudspeakers (for instance using an electromotor installed in each of the loudspeakers). By taking these measures, the audio playback quality may be improved particularly at a special spatial area or point (which may be user-defined or which may be the position at which a listener is currently located or which can be a center of gravity of the loudspeakers). Thus, a user- friendly system may be provided which allows to automatically configuring the loudspeaker system in an appropriate manner even in a scenario in which a user has installed the loudspeakers in an incorrect manner.
Embodiments of the invention may take into account orientation properties of loudspeakers (having, in reality, directivity instead of being purely omni-directional). Thus, improper orientation may be compensated and it may thus be ensured that the loudspeaker points into the direction of a listener. Particularly, by considering transfer functions of an audio system, a frequency-amplitude characteristic may be taken into account for correcting the audio system properties.
It is possible to equip each of the speakers with an assigned microphone. Alternatively, it is possible to equip only a part of the speakers (for instance a single one or a group of the speakers) with an assigned microphone.
According to an exemplary embodiment, automatic loudspeaker orientation correction may be provided. In such an embodiment, a surround sound system may be provided comprising at least two loudspeakers, each equipped with a (closely positioned) microphone. The surround sound system may further comprise a unit for measuring acoustical transfer functions between all speakers. A unit for determining the orientation of the speakers based on the transfer functions may be foreseen. According to an exemplary embodiment, an audio signal to be rendered by the speakers may be corrected based on the orientation information.
Thus, exemplary embodiments of the invention may not only have the capability that loudspeakers equipped with a microphone can automatically provide loudspeaker and/or room acoustics correction, but also the orientation of the loudspeakers may be taken into account. In other words, exemplary embodiments of the invention do not have to assume the loudspeaker to be omni-directional and may provide specific means to correct its (possibly) wrong orientation with respect to a listening position. According to an exemplary embodiment, automatic acoustic compensation in surround sound systems may be made possible.
According to an exemplary embodiment, a method for automatically correcting a wrong orientation of the loudspeakers in a home theatre (for instance in a 5.1 system, denoting a stereo format utilizing three primary channels (left, center, right), two surround channels (left surround, right surround) and an LFE channel, which is the ".1" channel because it uses approximately one-tenth of the bandwidth of a full- frequency channel) system based on the normalization of high frequency energy level contained in cross loudspeaker transfer functions may be made possible.
One aspect of home theatre systems is the loudspeaker setup and its calibration to the listener position. Quite often, it may happen that some loudspeakers are not properly connected (for instance polarity inversion, left/right inversion, etc.), and sometimes even not unpacked at all. According to an exemplary embodiment of the invention, an automated home theatre calibration system may be provided to improve a configuration of a loudspeaker setup, particularly with regard to orientation. It may be advantageous that automatic home theatre calibration systems have a room correction feature. An issue is to compensate the acoustics of the loudspeakers in the listening room in order to get an improved or optimal ("flat") response at the listening position. To achieve this, it is conventionally possible to place a microphone at the listener position. Possible corrections with a microphone at the listener positions are: level correction: compensation of the level (amplitude) differences between the different loudspeakers delay correction: ensures all loudspeaker signals arrive simultaneously at the listener position low frequency room acoustics correction: compensation of low frequency loudspeaker response and of the room (anti-)resonances and modes high frequency room acoustics correction: compensation of the high frequency loudspeaker response, of the room response and of the wrong orientation of the loudspeaker boxes. However, from a user perspective, merely placing a specific accessory (for instance a microphone) at the listener position during the calibration procedure is not user- friendly, particularly in terms of "Sense and Simplicity".
Therefore, exemplary embodiments of the invention are based on the recognition that the following reasoning holds: what parts of the possible improvements listed above would be possible if each loudspeaker box would be equipped with one microphone, without having a microphone at the listener position. Actually, it is not only possible to compute the geometrical configuration of the loudspeakers (by means of delay calculations). But it is also desirable to compensate for the wrong orientation of the loudspeaker boxes and simultaneously perform a high frequency room acoustics correction. According to an exemplary embodiment of the invention, a system for automatically correcting a possibly wrong orientation of two, three, four, five, six, seven or more loudspeakers in a home theatre (for instance in a 5.1) system may be made possible by normalizing particularly high frequency energy level contained in the loudspeaker transfer functions. The transfer function having the most energy at high frequencies may be considered as a reference.
The term "transfer function" may describe the transfer characteristics of a system or equipment. It may relate to the relationship between an input and an output of the system or equipment in terms of the transfer characteristics. The term "acoustical transfer function" between loudspeakers/microphones may relate to properties of an acoustical transfer in an acoustic field between the loudspeakers (including the microphones connected thereto), determinable on the basis of electric signals derived from the detection of acoustical audio signals. The transfer function may relate to the process by which an audio source wave passes through the space and is detected elsewhere. More particularly, a transfer function may be indicative of the transformation encountered by sound when passing from a source (like a loudspeaker) to a destination (like a microphone or a listener). The transfer function may be amplitude versus frequency curve indicative of the sound characteristic of the audio system. For instance, when a "white" audio signal is emitted by a loudspeaker and detected by a microphone, the characteristic of the loudspeaker-microphone system may transfer the white audio signal into a frequency-amplitude curve. In an audio system comprising two microphones ands two loudspeakers, four transfer functions may be measured (microphone 1 -loudspeaker 1, microphone 1 -loudspeaker 2, microphone 2-loudspeaker 1, microphone 2- loudspeaker 2).
In the following, some aspects concerning loudspeaker directivity of exemplary embodiments of the invention will be explained.
A loudspeaker box has a frequency dependent directivity characteristic. At low frequencies, a loudspeaker driver may act as a pure piston and the radiated sound field may be omni-directional. At high frequencies, the loudspeaker becomes more directive because the loudspeaker driver diameter becomes large relative to the wavelength. Therefore, a bad loudspeaker orientation can strongly effect the reproduction particularly of high frequencies.
Moreover, another aspect of bad loudspeaker orientation in a listening room is that if a loudspeaker box is pointing towards the wall, the wall may reflect a significant amount of energy back to the listening area. Because walls have a rather absorbent behavior, these reflected waves will also experience a low pass filtering that will also affect the overall frequency balance.
Exemplary fields of application of the embodiments of the invention are sound reproduction systems equipped with multiple (for instance at least two) loudspeakers, such as stereo (for instance portable) systems, and home theatre systems (for instance 5.1, 7.1, etc.).
Next, further exemplary embodiments of the invention will be explained. In the following, further exemplary embodiments of the device for processing audio data will be explained. However, these embodiments also apply for the method, for the computer- readable medium and for the program element.
The calculation unit may be adapted to calculate acoustical transfer functions between each pair of the plurality of speakers based on the audio data detected by the plurality of microphones. In such a scenario, at one time, one of the loudspeakers may emit an acoustical (test) signal, which acoustical (test) signal may be detected by all microphones assigned to the other loudspeakers. Transfer functions may be derived from this information. After this, the next loudspeaker may emit an audio signal and the microphones assigned to the remaining loudspeakers detect the corresponding audio signals. By taking this measure, all loudspeakers serve sequentially as an audio source and the microphones detect the corresponding audio signals as a basis for deriving the acoustical transfer functions. This procedure allows deriving all information necessary to analyze the systems. If desired, correction instructions may be provided so as to correct the orientation or acoustical emission properties of the loudspeakers.
The determining unit may be adapted to determine the orientation information indicative of the spatial positions and/or of the audio emission direction of the plurality of speakers. From the calculated acoustical transfer functions, applying basic mathematical procedures, the orientations and positions of the loudspeakers may be determined (for instance by evaluating intensities, applying damping models, analyzing delays, analyzing correlations between different signals, evaluating frequency information, considering directivity characteristics, evaluating propagation times in combination with propagation velocities, etc.). This orientation and position information may serve as a basis for correcting the setup of the speakers. At least a part of the plurality of speakers and the assigned one of the plurality of the microphones may be accommodated in a separate casing. In other words, a plurality of modules or separate entities may be provided, wherein each microphone and the corresponding loudspeaker may be provided in a separate housing. This may allow for a spatially distributed audio configuration and therefore a high quality audio performance. A correction unit may be provided and may be adapted to correct an audio playback characteristic of at least a part of the plurality of speakers based on the determined orientation information. Therefore, after having analyzed the proper audio emission properties of the speakers, the correction unit may adjust the audio playback characteristics of the speakers so as to improve the audio performance. For instance, the audio playback characteristics may be improved or even optimized for a predetermined listening position. This listening position may be a user-defined position (for instance defined by a user of the sound system via an user interface), a geometrical center of the plurality of speakers (which may be calculated based on the knowledge at which positions the loudspeakers are positioned), or a position defined with respect to a given component of an audio system (for instance improving the sound quality in front of a television where a user is usually sitting when using the sound system).
The adjusted audio playback characteristic may comprise an amplitude of the audio playback of an individual one of the speakers, of a part of the speakers or of all speakers, a frequency filtering characteristics (for instance the definition of cut-off frequencies or frequency bands), and an equalizer characteristic. These are only examples and may be substituted by or combined with any other audio playback characteristics.
The device may further comprise a correction unit that is adapted to correct the orientation of at least a part of the plurality of speakers based on the determined orientation information. In other words, the speakers may also be provided to be movable (for instance adapted for a translational movement and/or for a rotational movement). For this purpose, an electric motor may be provided, or the devices may simply be foreseen to be movable by a user. In the latter case, the user may be provided or guided by the device with an instruction as to how to modify a position and/or an orientation of one of the speakers to improve playback quality.
The calculation unit may be adapted to calculate the acoustical transfer functions between the plurality of speakers based on components of the audio data which components exceed a predetermined frequency threshold (of, for instance, several kHz). For instance, high frequencies may be particularly suitable to be analyzed in accordance with exemplary embodiments of the invention, since directivity of a loudspeaker is usually higher at high frequencies than at low frequencies. In other words, a loudspeaker is essentially omnidirectional at low frequencies and shows directional behavior at high frequencies. Therefore, an evaluation in the high frequency domain may derive more meaningful results with regard to orientation. Such a frequency threshold or transition frequency may be in the range of 500 Hz to 20 kHz, particularly in the range of 1 kHz to 5 kHz, more particularly in the range of 2 kHz to 4 kHz. Thus, specifically such a high frequency range may be subject of the investigations. Although the given exemplary numbers for the transition frequency may be valid for many loudspeakers, it should be kept in mind that this frequency value, at which a transition between an omni-directional behavior and a directive behavior occurs, is usually smaller, the larger the loudspeaker is. More generally, the value may be dependent on the size of the loudspeaker and consequently dependent on the size of an acoustical cone emitted by the loudspeaker. In the following, the technical definition of the so-called "piston range of a cone loudspeaker" will be given. The piston range, where a loudspeaker cone is considered as being omnidirectional, is technically defined by:
k a < 1
where "k" is the wave number and "a" the loudspeaker cone radium in meters. For k a > 1, the loudspeaker cone starts to be more and more directional as frequency increases.
Furthermore, the way the loudspeaker is mounted may have an influence on the frequency value.
At least a part of the plurality of microphones may be omni-directional microphones. The term omni-directional may relate to a not directional component. It may denote receiving sound waves in or from any direction, particularly so-called 360° receiving capability. The device for processing audio data may be realized as at least one of the group consisting of an audio surround system, a stereo audio system, a mobile phone, a headset, a hearing aid, a hands free system, a television device, a video recorder, a monitor, a gaming device, a laptop, an audio player, a DVD player, a CD player, a hard disk-based media player, an internet radio device, a public entertainment device, a portable audio player, an MP3 player, a hi-fi system, a vehicle entertainment device, a car entertainment device, a medical communication system, a body-worn device, a speech communication device, a home cinema system, and a music hall system.
However, although the system according to an embodiment of the invention primarily intends to improve the quality of sound or audio data, it is also possible to apply the system for a combination of audio data and visual data. For instance, an embodiment of the invention may be implemented in audiovisual applications like a portable video player in which multiple speakers are used.
It is further possible to use, instead of a single microphone assigned to each speaker, a plurality of microphones assigned to a particular speaker. By averaging the signals captured by the plurality of microphones assigned to a particular speaker, it is possible, with improved accuracy, to derive information to compensate for inaccurate speaker orientation.
The aspects defined above and further aspects of the invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to these examples of embodiment. BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited. Fig. 1 shows an audio processing system according to an exemplary embodiment of the invention.
Figs. 2A and 2B shows an audio playback system in two different configurations according to exemplary embodiments of the invention.
Figs. 3 A and 3B illustrates a method of calibrating an audio processing system according to an exemplary embodiment of the invention.
Fig. 4 shows a flow diagram illustrating a method of processing audio data according to an exemplary embodiment of the invention.
DESCRIPTION OF EMBODIMENTS The illustration in the drawing is schematically. In different drawings, similar or identical elements are provided with the same reference signs.
In the following, referring to Fig. 1, an audio processing system 100 according to an exemplary embodiment of the invention will be explained.
The audio processing system 100 comprises a first microphone 101, a second microphone 102, a third microphone 103 and a fourth microphone 104. The number of microphones may be larger or smaller than four, particularly may be larger than or equal to two. Each of the microphones 101 to 104 is adapted to detect audio data emitted by anyone of a plurality of loudspeakers, namely a first loudspeaker 105, a second loudspeaker 106, a third loudspeaker 107 and a fourth loudspeaker 108. As can be taken from Fig. 1, a first housing 109 is provided in which the first microphone 101 and the first loudspeaker 105 are accommodated or integrated. The second microphone 102 and the second loudspeaker 106 are embedded in a second housing 110. The third microphone 103 and the third loudspeaker 107 are provided within a third housing 111. A fourth housing 112 accommodates the fourth microphone 104 and the fourth speaker 108. Therefore, each of the microphones 101 to 104 has an assigned speaker 105 to 108, and these pairs are located directly neighbored or adjacent to one another. The loudspeakers 105 to 108 are each adapted to emit acoustic waves and are each equipped with the corresponding microphone 101 to 104. In normal use, the audio system 100 is used for reproducing audio content and may serve as an audio surround system. However, the system 100 also has an automatic loudspeaker orientation configuration feature that will be explained in the following in more detail. With respect to the actual audio playback functionality of a surround system, no further details will be explained in the following.
As can be taken from Fig. 1, each of the microphones 101 to 104 is electrically coupled to a calculation unit 113 so as to provide detected audio data 114 to 117 to the calculation unit 113. The calculation unit 113 is adapted to calculate acoustical transfer functions between the plurality of speakers 105 to 108 based on the audio data 114 to 117 detected by the plurality of microphones 101 to 104.
For example, in a first operation state, only the first loudspeaker 105 emits audio data and the microphones 102 to 104 detect the corresponding audio signals 115 to 117. Then, the second speaker 106 emits an audio signal which is detected by the microphones 101, 103, 104, and so on. From the corresponding data that are detected by the microphones 101 to 104, the calculation unit 113 may calculate all acoustical transfer functions indicative of the acoustical properties of the system and indicative of the present orientation of the speakers 105 to 108 with respect to one another.
The determined acoustical transfer functions 118 are supplied to a determining unit 119 adapted to determine orientation information indicative of the relative orientation of the plurality of speakers 105 to 108 based on the calculated acoustical transfer functions 118. Therefore, the determining unit 119 determines the orientation (that is to say the spatial positions and/or the directions) of the speakers 105 to 108 so as to determine whether there is a need to modify the configuration of the loudspeakers arrangement to improve playback quality. Corresponding orientation information 120 may be supplied to a correction unit 121 adapted to correct an audio playback characteristic of one or more of the loudspeakers 105 to 108 based on the determined orientation information 120. For this purpose, control signals 122 can, if needed, be provided to the corresponding loudspeakers 105 to 108 to improve the audio performance. Particularly, the correction unit 121 may calculate the control parameters 122 in such a manner that an audio quality is improved at a predetermined listening position (for instance a position at which a listener is presently or usually located). A user may input such a position to the system 100 via a user interface device 123. Such an I/O device may include a graphical user interface (GUI) having an LCD, a plasma device, or a cathode ray tube. Furthermore, input elements can be provided at the user interface 123 like a keypad, a joystick, buttons, a trackball, or even a microphone of a voice recognition system.
The control parameters 122 may alter amplitude of any signal to be reproduced by one of the loudspeakers 105 to 108, or may alter a frequency behavior, or may alter equalizer characteristics, or a spatial position of the microphones 105 to 108. Therefore, if needed, one or more of the loudspeakers 105 to 108 may be mechanically turned or shifted.
In the following, referring to Fig. 2 and Fig. 3, further aspects of an exemplary embodiment of the invention will be explained.
Fig. 2 shows a typical home theatre system setup in an ideal configuration 200 and in a non-ideal configuration 250.
Loudspeakers 105 to 108 are shown which are distributed around a human listener 201. Furthermore, a television 202 is shown which may also comprise one or more loudspeakers, wherein such a "center speaker" is assumed to be at the same position as the TV 202. In the "ideal" configuration 200 as shown in Fig. 2A, all loudspeaker boxes
105 to 108 point towards the listener 201. But in many cases, as for instance shown in Fig. 2B for non-ideal configuration 250, the loudspeaker boxes 105 to 108 do not have an optimum orientation and will be pointing outside a listening area 203.
In the present embodiment, all loudspeakers 105 to 108, 202 are equipped with one omni-directional microphone (101 to 104, 204). This enables the measurement of the acoustical transfer functions between all loudspeakers 105 to 108, 202, the so-called "cross loudspeaker transfer functions". It is possible to make use of these transfer functions to get an idea of the orientation of the loudspeaker boxes 105 to 108, 202 with respect to the listener 201 and to provide the necessary corrections. Fig. 3 shows two examples of cross loudspeaker transfer function measurements.
In a first scenario 300, the loudspeaker box 1 is properly oriented. In a second scenario 350, the loudspeaker 4 is wrongly oriented.
In the first scenario 300 as shown in Fig. 3A, the transfer functions between loudspeaker 1 and the others are measured. This may give an idea on the directivity of loudspeaker box 1. Because the directivity of a loudspeaker driver increases with frequency, a comparison of the high frequency content of the transfer functions can provide an idea of orientation of loudspeaker 1. Because the positions of the loudspeaker boxes can be computed, it can be possible, by interpolation, to estimate the high frequency energy level reaching the center of the listening area 203, where the listener 201 is assumed to be sitting. In the second scenario 350 as shown in Fig. 3B, it is the directivity of loudspeaker 4 that is measured. In this case, the other loudspeakers will get much less high frequency energy than in the first scenario 300, which indicates that loudspeaker 4 is most likely wrongly oriented. By computing the level of high frequencies reaching the middle of the listening area 203 for the second scenario 350 and by comparing it with its level for the first scenario 300, a high frequency boost filter to be applied to loudspeaker 4 can be derived.
In the following, referring to Fig. 4, a block diagram 400 will be explained illustrating a method of processing audio data according to an exemplary embodiment of the invention. Such a method may work according to the following process:
All cross loudspeaker transfer functions are measured, see block 410. The loudspeaker positions are computed (for instance by evaluating intensities, applying damping models, analyzing delays, analyzing correlations between different signals, evaluating frequency information, considering directivity characteristics, evaluating propagation times in combination with propagation velocities, etc.), see block 420.
The listening position is user-defined or assumed to be the geometrical center of the area enclosed by the loudspeakers, or assumed to be in front of the TV set, see block 430. For each loudspeaker, the high frequency energy level radiated in the direction of the listening position is computed by interpolating the high frequency content of the different cross loudspeaker measurements. Because of the oval shape of the loudspeaker directivity, the interpolation may be non-linear, see block 440.
The high frequency energy levels of all loudspeakers are normalized to the highest one. In other words, the high frequency energy radiated towards the listening position is made equal for all loudspeakers, and preferably equal to the highest high frequency energy level value, see block 450.
It should be noted that the term "comprising" does not exclude other elements or features and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined.
It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.

Claims

CLAIMS:
1. A device (100) for processing audio data, wherein the device (100) comprises at least one microphone (101 to 104) each adapted to detect audio data (114 to
117); a plurality of speakers (105 to 108) each adapted to emit acoustic waves, wherein at least a part of the plurality of speakers (105 to 108) is provided with an assigned one of the at least one microphone (101 to 104); a calculation unit (113) adapted to calculate acoustical transfer functions (118) between the plurality of speakers (105 to 108) based on the audio data (114 to 117) detected by the at least one microphone (101 to 104); a determining unit (119) adapted to determine orientation information (120) indicative of the relative orientation of the plurality of speakers (105 to 108) based on the calculated acoustical transfer functions (120).
2. The device (100) according to claim 1, wherein the calculation unit (113) is adapted to calculate the acoustical transfer functions (118) for each pair of the plurality of speakers (105 to 108) based on the audio data (114 to 117) detected by the at least one microphone (101 to 104).
3. The device (100) according to claim 1, wherein the determining unit (119) is adapted to determine the orientation information (120) indicative of a spatial position and/or of an audio emission direction of the plurality of speakers (105 to 108).
4. The device (100) according to claim 1, wherein, for at least a part of the plurality of speakers (105 to 108), a respective one of the plurality of speakers (105 to 108) and the assigned one of the at least one microphone (101 to 104) are accommodated in a separate casing (109 to 112).
5. The device (100) according to claim 1, comprising a correction unit (121) adapted to correct an audio playback characteristic of at least a part of the plurality of speakers (105 to 108) based on the determined orientation information (121).
6. The device (100) according to claim 1, comprising a correction unit (121) adapted to correct the orientation of at least a part of the plurality of speakers (105 to 108) based on the determined orientation information (120).
7. The device (100) according to claim 5 or 6, wherein the correction unit (121) is adapted to correct the audio playback characteristic so as to improve an audio quality at a predetermined listening position.
8. The device (100) according to claim 5 or 6, wherein the predetermined listening position is one of the group consisting of a user-defined position, a geometrical center of the plurality of speakers (105 to 108), and a position defined with respect to a defined component (202) of an audio playback system comprising the device (100).
9. The device (100) according to claim 5, wherein the audio playback characteristic comprises at least one of an amplitude, a frequency filtering characteristic, and an equalizer characteristic.
10. The device (100) according to claim 1, wherein the calculation unit (119) is adapted to calculate the acoustical transfer functions (120) between the plurality of speakers (105 to 108) selectively based on components of the audio data (114 to 117) which components exceed a predetermined frequency threshold value.
11. The device (100) according to claim 10, wherein the predetermined frequency threshold value is in the range between essentially 1 kHz and essentially 5 kHz.
12. The device (100) according to claim 1, wherein at least one of the at least one microphone (101 to 104) is an omnidirectional microphone.
13. The device (100) according to claim 1, realized as at least one of the group consisting of an audio surround system, a stereo audio system, a mobile phone, a headset, a hearing aid, a hands free system, a television device, a video recorder, a monitor, a gaming device, a laptop, an audio player, a DVD player, a CD player, a hard disk-based media player, an internet radio device, a public entertainment device, a portable audio player, an MP3 player, a hi-fi system, a vehicle entertainment device, a car entertainment device, a medical communication system, a body- worn device, a speech communication device, a home cinema system, and a music hall system.
14. A method of processing audio data (114 to 117), wherein the method comprises detecting audio data (114 to 117) using at least one microphone (101 to 104); emitting acoustic waves using a plurality of speakers (105 to 108), wherein at least a part of the plurality of speakers (105 to 108) is provided with an assigned one of the at least one microphone (101 to 104); calculating acoustical transfer functions (118) between the plurality of speakers (105 to 108) based on the audio data (114 to 117) detected by the at least one microphone (101 to 104); determining orientation information (120) indicative of the relative orientation of the plurality of speakers (105 to 108) based on the calculated acoustical transfer functions (118).
15. A computer-readable medium, in which a computer program of processing audio data (114 to 117) is stored, which computer program, when being executed by a processor (113, 119), is adapted to carry out or control a method according to claim 14.
16. A program element of processing audio data (114 to 117), which program element, when being executed by a processor (113, 119), is adapted to carry out or control a method according to claim 14.
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