Audio reproduction system and method for reproducing an audio signal

• US 7,706,544 B2
• Filed: 04/05/2005
• Issued: 04/27/2010
• Est. Priority Date: 11/21/2002
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Sporer, Thomas, Land, Carsten, Kutschbach, Haymo, Schlenker, Berthold, Röder, Thomas, Brix, Sandra, Beckinger, Michael, Melchior, Frank
• Primary Examiner(s): Chin; Vivian
• Assistant Examiner(s): SUTHERS, DOUGLAS JOHN
• Application Number:
  US11/099,156
• Publication Number:
  US 20050175197A1
• Time in Patent Office: 1,848 Days
• Field of Search: 381/17, 381/18, 381/19, 381/309, 381/310, 381/27, 381/61, 381/307
• US Class Current: 381/18
• CPC Class Codes: H04R 1/403 loud-speakers
• CPC Class Codes: H04R 3/12 for distributing signals to two or more loudspeakers specially adapted for hearing aids H04R25/407
• CPC Class Codes: H04R 5/02 Spatial or constructional arrangements of loudspeakers
• CPC Class Codes: H04S 2420/13 Application of wave-field synthesis in stereophonic audio systems
• CPC Class Codes: H04S 3/00 Systems employing more than two channels, e.g. quadraphonic H04S5/00, H04S7/00 take precedence

Abstract

An audio reproduction system is divided into a central wave-field synthesis module and a plurality of loudspeaker modules disposed in a distributed way, wherein synthesis signals for the individual loudspeakers as well as corresponding channel information associated to the synthesis signals are calculated in the central wave-field synthesis module. The synthesis signals for a loudspeaker as well as associated channel information will then be transmitted to respective loudspeaker modules via a transmission path, wherein every loudspeaker module obtains the synthesis signals and associated channel information intended for the loudspeaker associated to the loudspeaker module. A distributed audio rendering and digital/analog converting takes place in the loudspeaker module to generate the actually analog loudspeaker signals in a distributed way in spatial proximity to every loudspeaker. The division into a central wave-field synthesis module and the plurality of distributed loudspeaker modules allows that audio reproduction systems that are scalable with regard to the price can be generated in order to offer systems of different size scalable in price particularly for cinema reproduction rooms varying strongly in size.

Claims

1. An audio reproduction system for a reproduction room, in which a plurality of loudspeakers are disposed at a plurality of defined loudspeaker positions, wherein an audio signal with a plurality of audio tracks is used, wherein a different virtual audio source position is associated to each audio track of the plurality of audio tracks, the audio reproduction system comprising:

a central wave-field synthesis module, formed to

determine, for each virtual audio source position of the plurality of audio tracks, audio channel information for an audio channel from the virtual audio source position to a defined loudspeaker position of the plurality of defined loudspeaker positions, wherein the audio channel information is obtained for each channel from each virtual audio source position of the plurality of audio tracks to each loudspeaker of the plurality of loudspeakers,

calculate synthesis signals for the plurality of loudspeakers using amplitude scaling and time delaying the plurality of audio tracks, wherein the synthesis signals for the plurality of loudspeakers for each audio track of the plurality of audio tracks associated with the different virtual audio source positions are obtained, and

supply the synthesis signals calculated for the plurality of audio tracks associated with the different virtual audio source positions and the audio channel information for each virtual audio source position of the plurality of audio tracks to each loudspeaker of the plurality of;

a plurality of loudspeaker modules, wherein each loudspeaker module of the plurality of loudspeaker modules being associated to at least one loudspeaker of the plurality of loudspeakers, and wherein each loudspeaker module of the plurality of loudspeaker modules comprises;

a receiver for receiving the synthesis signals for the respective at least one loudspeaker for each virtual audio source position of the plurality of audio tracks and the audio channel information for each virtual audio source position to the respective at least one loudspeaker;

a renderer for calculating a reproduction signal for the respective at least one loudspeaker by using the synthesis signals for each virtual audio source position of the plurality of audio tracks and the audio channel information for each virtual audio source position to the respective at least one loudspeaker; and

a signal processor for generating an analog loudspeaker signal from the reproduction signal for the respective at least one loudspeaker; and

a plurality of transmission paths from the central wave-field synthesis module to each loudspeaker module of the plurality of loudspeaker modules, wherein each transmission path is coupled to the central wave-field synthesis module on the one hand and to an individual loudspeaker module of the plurality of loudspeaker modules on the other hand.

2. The audio reproduction system of claim 1, wherein each loudspeaker module of the plurality of loudspeaker modules is combined with the loudspeaker to which the same is associated, so that a spatial distance between the loudspeaker and the loudspeaker module is smaller than a spatial distance between the loudspeaker module and the central wave-field synthesis module.

3. The audio reproduction system of claim 1, wherein the audio channel information is impulse responses for the audio channels.

4. The audio reproduction system of claim 3, wherein the renderer for calculating a reproduction signal has a convoluter to perform one or several convolutions by using the one or several synthesis signals with the respective impulse responses.

5. The audio reproduction system of claim 4, wherein the renderer comprises:

a time domain frequency domain converter for each synthesis signal;

a multiplier for each synthesis signal;

a summator for summing synthesis signals provided with respective channel impulse responses present in the frequency domain; and

a single frequency-domain time-domain converter for converting the sum signal into the time domain to obtain the reproduction signal.

6. The audio reproduction system of claim 1, wherein the signal processor in the loudspeaker module has a digital amplifier.

7. The audio reproduction system of claim 4, wherein the central wave-field synthesis module is formed to transmit a first part of the channel impulse response sample by sample and a second part merely by using envelope support values, and

wherein the renderer is formed to reconstruct the second part of the channel impulse response by using the supporting values.

8. The audio reproduction system of claim 7, wherein the renderer is formed to generate the second part of the channel impulse response by a noise generator or pseudo-noise generator, wherein noise values or pseudo noise values are weighted in amplitude with the support values and/or auxiliary values interpolated from the support values.

9. The audio reproduction system of claim 1, wherein the audio tracks are standardized multi channel tracks and the audio source positions are standard positions relating to a positioning of reproduction loudspeakers in a reproduction room, wherein the number of standard positions is equal to the number of standardized multi channel tracks.

10. The audio reproduction system of claim 9, wherein the wave-field synthesis module is formed to calculate the virtual audio source positions for calculating the audio channel information from the standard position.

11. The audio reproduction system of claim 10, wherein the wave-field synthesis module is formed to place the virtual audio source positions in infinity, so that the plurality of loudspeakers together emit plane sound waves.

12. The audio reproduction system of claim 10, wherein the wave-field synthesis module is formed to simulate virtual reproduction loudspeakers at defined virtual reproduction loudspeaker positions as point-shaped sound sources, which are so far away from the plurality of loudspeakers that an optimum reproduction region generally comprises the whole reproduction room.

13. The audio reproduction system of claim 9, wherein the audio tracks are part of a video or cinema film, wherein the wave-field synthesis module is formed to sample the audio tracks of the video or cinema films shifted by a time period prior to a video reproduction, wherein the time period is chosen to obtain a simultaneous reproduction of image and sound under consideration of a processing time in the wave-field synthesis module and the loudspeaker module.

14. The audio reproduction system of claim 1, wherein the audio signal comprises, as an audio track of the plurality of audio tracks, an audio signal of an object as well as a position of the audio object in the recording environment, one or several characteristics of the audio objects, such as size or density and/or information about acoustic characteristics of a recording environment.

15. The audio reproduction system of claim 14, wherein the wave-field synthesis module is formed to determine the virtual audio source positions from positions of the audio objects in the recording environment.

16. The audio reproduction system of claim 1, wherein the wave-field synthesis module is formed to obtain information about acoustic characteristics of the reproduction room and consider them when determining the audio channel information, so that the sound waves reproduced by the plurality of loudspeakers are formed such that the acoustic influences of the reproduction room are reduced.

17. The audio reproduction system of claim 1, wherein the wave-field synthesis module is formed to perform an adaptation to an acoustic of the reproduction room prior or during a reproduction of the audio signal, by

calculating a plurality of room impulse response between the loudspeaker and microphones positioned in the reproduction room,

interpolating an overall impulse response of the reproduction room from the plurality of room impulse responses, and

considering the overall impulse response when calculating the audio channel information to reduce acoustic characteristics of the reproduction room.

18. The audio reproduction system of claim 1, wherein the central wave-field synthesis module is formed to generate synchronization information and to embed it into data streams to the loudspeaker modules, and wherein the plurality of loudspeaker modules is formed to receive the synchronization information from the central wave-field synthesis module and to use it for synchronization, so that the loudspeaker modules are synchronized to the central wave-field synthesis module.

19. A method for reproducing an audio signal in a reproduction room, in which a plurality of loudspeakers are disposed at a plurality of defined loudspeaker positions, wherein an audio signal with a plurality of audio tracks is used, wherein a different virtual audio source position is associated to each audio track of the plurality of audio tracks, comprising:

centrally determining, for each virtual audio source position of the plurality of audio tracks, audio channel information for an audio channel from the virtual audio source position to a defined loudspeaker position of the plurality of defined loudspeaker positions, wherein the audio channel information is obtained for each channel from each virtual audio source position of the plurality of audio tracks to each loudspeaker of the plurality of loudspeakers;

centrally determining synthesis signals for the plurality of loudspeakers using amplitude scaling and time delaying the plurality of audio tracks, wherein the synthesis signals for the plurality of loudspeakers for each audio track of the plurality of audio tracks associated with the different virtual audio source positions are obtained;

transmitting the synthesis signals calculated for the plurality of audio tracks associated with the different virtual audio source positions and the audio channel information for each virtual audio source position of the plurality of audio tracks to each loudspeaker of the plurality of loudspeakers to a plurality of loudspeaker modules, each loudspeaker module of the plurality of loudspeaker modules being associated to a respective at least one loudspeaker of the plurality of loudspeakers;

decentrally calculating a reproduction signal for the respective at least one loudspeaker by using the synthesis signals for each virtual audio source position of the plurality of audio tracks and the audio channel information for each virtual audio source position to the respective at least one; and

performing a signal processing by using a digital/analog conversion of the reproduction signal for the respective at least one loudspeaker to generate an analog loudspeaker signal.

20. A digital storage medium having stored thereon a computer program having a program code for performing a method:

for reproducing an audio signal in a reproduction room, in which a plurality of loudspeakers are disposed at a plurality of defined loudspeaker positions, wherein an audio signal with a plurality of audio tracks is used, wherein a different virtual audio source position is associated to each audio track of the plurality of audio tracks, comprising;

centrally determining, for each virtual audio source position of the plurality of audio tracks, audio channel information for an audio channel from the virtual audio source position to a defined loudspeaker position of the plurality of defined loudspeaker positions, wherein the audio channel information is obtained for each channel from each virtual audio source position of the plurality of audio tracks to each loudspeaker of the plurality of loudspeakers;

centrally determining synthesis signals for the plurality of loudspeakers using amplitude scaling and time delaying the plurality of audio tracks, wherein the synthesis signals for the plurality of loudspeakers for each audio track of the plurality of audio tracks associated with the different virtual audio source positions are obtained;

transmitting the synthesis signals calculated for the plurality of audio tracks associated with the different virtual audio source positions and the audio channel information for each virtual audio source position of the plurality of audio tracks to each loudspeaker of the plurality of loudspeakers to a plurality of loudspeaker modules, each loudspeaker module of the plurality of loudspeaker modules being associated to a respective at least one loudspeaker of the plurality of loudspeakers;

decentrally calculating a reproduction signal for the respective at least one loudspeaker by using the synthesis signals for each virtual audio source position of the plurality of audio tracks and the audio channel information for each virtual audio source position to the respective at least one loudspeaker; and

performing a signal processing by using a digital/analog conversion of the reproduction signal for the respective at least one loudspeaker to generate an analog loudspeaker signal.