Surround Sound System

• US 20130223658A1
• Filed: 08/22/2011
• Published: 08/29/2013
• Est. Priority Date: 08/20/2010
• Status: Active Grant

• Current Assignee: Callaghan Innovation
• Original Assignee: Callaghan Innovation
• Inventors: Poletti, Mark Alistair, Betlehem, Terence
• Granted Patent: US 9,319,794 B2
• Time in Patent Office: Days
• US Class Current: 381/307
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: H04R 5/02 Spatial or constructional arrangements of loudspeakers
• CPC Class Codes: H04S 2420/11 Application of ambisonics in stereophonic audio systems
• CPC Class Codes: H04S 3/002 Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution control circuits for electronic adaptation of the sound field H04S7/30

Abstract

A surround sound system for reproducing a spatial sound field in a sound control region within a room having at least one sound reflective surface. The system uses multiple steerable loudspeakers located about the sound control region, each loudspeaker having a plurality of different individual directional response channels being controlled by respective speaker input signals to generate sound waves emanating from the loudspeaker with a desired overall directional response. A control unit connected drives each of the loudspeakers and has pre-configured filters based on measured acoustic transfer functions for the room for filtering the input spatial audio signals to generate the speaker input signals for all the loudspeakers to generate sound waves with co-ordinated overall directional responses that combine together at the sound control region in the form of either direct sound or reflected sound from the reflective surface(s) of the room to reproduce the spatial sound field.

Claims

1. A surround sound system configured to reproduce a holographic spatial sound field in a sound control region within a room having at least one sound reflective surface, comprising:

multiple steerable loudspeakers located about the sound control region, each loudspeaker having a plurality of speaker input signals, each speaker input signal controlling one of a plurality of different individual directional beam response patterns which may be generated by the loudspeaker, and wherein the overall directional response of the sound waves emanating from the loudspeaker is that created by a combination of the individual directional beam response patterns as dictated by the speaker input signals; and

a control unit connected to each of the loudspeakers and which in a playback mode receives input spatial audio signals representing the holographic spatial sound field for reproduction in the sound control region, the control unit having pre-configured filters for filtering the input spatial audio signals to generate the speaker input signals for driving the loudspeakers to generate sound waves with respective overall directional responses that are co-ordinated to combine together at the sound control region to reproduce the holographic spatial sound field in the form of direct sound emanating into the sound control region directly from one or more loudspeakers and reflected sound emanating into the sound control region from the reflective surface(s) of the room, the filters of the control unit being pre-configured in a configuration mode prior to operating in playback mode based on acoustic transfer function data measured by a sound field recording system comprising a microphone array located in the sound control region and where the acoustic transfer function data represents the acoustic transfer functions measured by the microphone array in response to test signals generated by each of the loudspeakers for each of their individual directional beam response patterns at their respective locations in the room.

2. A surround sound system according to claim 1 wherein the input spatial audio signals are in an ambisonics-encoded surround format that is received and directly filtered by the filters in the control unit to generate the speaker input signals for the loudspeakers.

3. A surround sound system according to claim 1 wherein the input spatial audio signals are in a non-ambisonics surround format and the control unit further comprises a converter that is configured to convert the non-ambisonics input signals into an ambisonics surround format for subsequent filtering by the filters in the control unit to generate the speaker input signals for the loudspeakers.

4. A surround sound system according to claim 1 wherein the control unit is switchable between the configuration mode in which the control unit configures the filters for the room and the playback mode in which the control unit processes the input spatial audio signals for reproduction of the spatial sound field using the loudspeakers, and wherein the control unit comprises a configuration module that is arranged to automatically configure the filters in the configuration mode based on input acoustic transfer function data for the room that is measured by the sound field recording system.

6. A surround sound system according to claim 4 wherein the configuration module receives raw measured acoustic transfer function data from the sound field recording system and converts it into an ambisonics representation of the acoustic transfer function data which is used to configure the filters of the control unit.

7. A surround sound system according to claim 1 wherein the filters of the control unit are ambisonics loudspeaker filters.

8. A surround sound system according to claim 1 wherein the surround sound system is configured to provide a 2-D spatial sound field reproduction in a 2-D sound control region, and wherein the sound control region is circular and has a predetermined diameter.

10. A surround sound system according to claim 8 wherein the sound control region is located in a horizontal plane and the loudspeakers are at least partially co-planar with the sound control region.

11. A surround sound system according to claim 1 wherein each loudspeaker is located within a respective loudspeaker location region, the room being radially and equally segmented into loudspeaker location regions about the origin of the sound control region based on the number of loudspeakers, and wherein each loudspeaker region is defined to extend between a pair of radii boundary lines extending outwardly from the origin of the sound control region, and wherein the angular distance between each pair of radii boundary lines corresponds to 360°

/L, where L is the number of loudspeakers.

13. A surround sound system according to claim 1 wherein each loudspeaker is spaced apart from every other loudspeaker by at least half of a wavelength of the Schroeder frequency of the room within which the surround sound system operates.

14. A surround sound system according to claim 1 wherein each loudspeaker is spaced apart from any reflective surface(s) in the room by at least quarter of a wavelength of the Schroeder frequency of the room within which the surround sound system operates.

15. A surround sound system according to claim 1 wherein each loudspeaker is spaced at least 1 m from the center of the sound control region.

16. A surround sound system according to claim 15 wherein each loudspeaker is spaced at least 1.5 m from the center of the sound control region.

17. A surround sound system according to claim 1 wherein each loudspeaker is configured to generate overall directional responses having up to M^th order directivity patterns, where M is at least 1, and wherein the value of 2M+1 corresponds to the number of individual directional beam response patterns available for each loudspeaker.

18. A surround sound system according to claim 17 wherein each loudspeaker is configured to generate overall directional responses having up to M^th order directivity patterns, wherein M is equal to 4.

20. A surround sound system according to claim 17 wherein each loudspeaker comprises at least an individual directional beam response patterns corresponding to a first order directional response.

21. A surround sound system according to claim 17 wherein each loudspeaker comprises at least individual directional beam response patterns corresponding to 2M+1 phase mode directional responses.

22. A surround sound system according to claim 17 wherein each loudspeaker comprises at least individual directional beam response patterns corresponding to an omni-directional response, and cos(mφ

) and sin(mφ

) for m=1, 2, . . . , M, and where φ

is equal to the desired angular direction of the loudspeaker overall directional response relative to the origin of the loudspeaker.

23. A surround sound system according to claim 1 wherein the overall directional response of each loudspeaker is steerable in 360°

relative to the origin of the loudspeaker.

24. A surround sound system according to claim 1 wherein each loudspeaker comprises multiple drivers configured in a geometric arrangement with in a single housing, each driver being driven by a driver signal to generate sound waves, and wherein each loudspeaker further comprises a beamformer module that is configured to receive and process the speaker input signals corresponding to the individual directional beam response patterns of the loudspeaker and which generates driver signals for driving the loudspeaker drivers to create an overall sound wave having the desired overall directional response.

25. A surround sound system according to claim 1 wherein each loudspeaker comprises a housing within which a uniform circular array of monopole drivers of a predetermined radius are mounted, and wherein the number of drivers and radius is selected based on the desired maximum order of directivity pattern required for the loudspeaker, and wherein the monopole drivers are spaced apart from each other by no more than half a wavelength of the maximum frequency of the operating frequency range of the surround sound system.

27. A surround sound system according to claim 1 comprising at least four steerable loudspeakers.

28. A surround sound system according to claim 1 wherein the loudspeakers are equi-spaced relative to each other about the sound control region.

29. A surround sound system according to claim 1 wherein the spatial sound field is represented in the sound control region by direct sound in combination with first order, second order, and/or higher order reflections from sound waves reflected off one or more reflective surfaces of the room.

30. A surround sound system according to claim 1 wherein the surround sound system is configurable to reproduce higher order ambisonics spatial sound fields.

32. A surround sound system according to claim 1 wherein the diameter of the sound control region is in the range of about 0.175 m to about 1 m.

33. A surround sound system according to claim 1 wherein the surround sound system is configured to provide a 3-D spatial sound field reproduction in a 3-D sound control region, and wherein the 3-D sound control region is spherical in shape.

5. (canceled)

9. (canceled)

12. (canceled)

19. (canceled)

26. (canceled)

31. (canceled)

34. (canceled)

35. An audio device for driving multiple steerable loudspeakers to reproduce a holographic spatial sound field in a sound control region, each loudspeaker having a plurality of different individual directional beam response patterns being controlled by respective speaker input signals to generate sound waves emanating from the loudspeaker with a desired overall directional response created by a combination of the individual directional beam response patterns as dictated by the speaker input signals, and where the loudspeakers are located about a sound control region in a room having at least one sound reflective surface, the device comprising:

an input interface for receiving input spatial audio signals representing a holographic spatial sound field for reproduction in the sound control region;

a filter module comprising filters that are configurable based on acoustic transfer function data representing the acoustic transfer functions measured by a sound field recording system comprising a microphone array located in the sound control region and where the acoustic transfer function data represents the acoustic transfer functions measured by the microphone array in response to test signals generated by each of the loudspeakers for each of their individual directional beam response patterns at their respective locations in the room, and wherein the filters filter the input spatial audio signals to generate speaker input signals for driving the loudspeakers to generate sound waves with respective overall directional responses that are co-ordinated to combine together at the sound control region to reproduce the holographic spatial sound field in the form of direct sound emanating into the sound control region directly from one or more of the loudspeakers and reflected sound emanating into the sound control region from the reflective surface(s) of the room; and

an output interface for connecting to all the loudspeakers and for sending the speaker input signals to the loudspeakers.

36. An audio device according to claim 35 comprising wherein the input interface is configured to receive input spatial audio signals in an ambisonics-encoded surround format for direct filtering by the filters of the filter module to generate the speaker input signals for the loudspeakers.

37. An audio device according to claim 35 wherein the input interface is configured to receive input spatial audio signals in a non-ambisonics surround format and which further comprises a converter that is configured to convert the non-ambisonics input signals into an ambisonics surround format for subsequent filtering by the filters of the filter module to generate the speaker input signals for the loudspeakers.

38. An audio device according to claim 35 wherein the device is switchable between a configuration mode in which the device configures the filters of the filter module for the room and a playback mode in which the device processes the input spatial audio signals for reproduction of the spatial sound field using the loudspeakers, and wherein the device further comprises a configuration module that is arranged to automatically configure the filters of the filter module in the configuration mode based on input acoustic transfer function data for the room that is measured by the sound field recording system.

40. An audio device according to claim 38 wherein the configuration module receives raw measured acoustic transfer function data from the sound field recording system and converts it into an ambisonics representation of the acoustic transfer function data which is used to configure the filters of the filter module.

41. An audio device according to claim 35 wherein the filters of the filter module are ambisonics loudspeaker filters.

39. (canceled)