Center channel enhancement of virtual sound images

• US 6,853,732 B2
• Filed: 06/01/2001
• Issued: 02/08/2005
• Est. Priority Date: 03/08/1994
• Status: Expired due to Fees

• Current Assignee: IMAX Corporation
• Original Assignee: Sonics Associates, Incorporated (IMAX Corporation)
• Inventors: Scofield, William Clayton
• Primary Examiner(s): Mei, Xu
• Application Number:
  US09/872,671
• Publication Number:
  US 20020006206A1
• Time in Patent Office: 1,348 Days
• Field of Search: 381/309, 381/310, 381/1, 381/17, 381/18, 381/26, 381/74, 381/304, 381/305, 381/300
• US Class Current: 381/27
• CPC Class Codes: H04R 2420/07 Applications of wireless loudspeakers or wireless microphones
• CPC Class Codes: H04R 5/033 Headphones for stereophonic communication details thereof, e.g. relating to batteries, cables or control elements H04R1/10
• CPC Class Codes: H04S 1/005 For headphones
• CPC Class Codes: H04S 2400/01 Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved
• CPC Class Codes: H04S 2400/05 Generation or adaptation of centre channel in multi-channel audio systems
• CPC Class Codes: H04S 2420/01 Enhancing the perception of the sound image or of the spatial distribution using head related transfer functions [HRTF's] or equivalents thereof, e.g. interaural time difference [ITD] or interaural level difference [ILD]
• 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
• CPC Class Codes: H04S 5/00 Pseudo-stereo systems, e.g. in which additional channel signals are derived from monophonic signals by means of phase shifting, time delay or reverberation

Abstract

The present invention disclosed and claimed herein, in one aspect thereof, comprises a method for enhancing the front sound image during reproduction in a listening space of a stereo sound program, comprising the steps of receiving left and right channels of the stereo sound program; generating a virtual center channel signal from the left and right channels of the stereo sound program; and driving a center channel speaker with the virtual center channel signal, the center channel speaker disposed at a central location in a front portion of the listening space.

Claims

1. A method for enhancing the front sound image from a listening position during reproduction in a listening space of a stereo sound program, comprising the steps of:

receiving left and right channels of the stereo sound program;

generating a virtual center channel signal from the left and right channels of the stereo sound program;

driving a physical center channel speaker with the virtual center channel signal; and

producing a virtual sound source at a central location in a front portion of the listening space dispose between the physical center channel speaker and a listener position, said virtual sound source produced by a combination of physical left and right speakers disposed proximate the right and left ears of a listener a d the physical center channel speaker.

2. The method of claim 1, wherein the step of generating comprises the steps of:

processing the left and right channels of the stereo sound program in first and second networks respectively, while substantially maintaining the original overall bandwidth in each left and right channel and providing first left and right output signals each having an output level substantially corresponding to the respective original left and right channel signal levels;

blending the processed first left and right output signals to provide the virtual center channel signal; and

conditioning the virtual center channel signal for driving the center channel loudspeaker.

3. The method of claim 2, wherein the step of processing further comprises the step of:

redistributing the spectral content of each left and right input channel within the audible range of frequencies.

4. The method of claim 3, wherein the step of redistributing the spectral content of each respective channel comprises the steps of:

applying the respective signal to the input of a comb filter network having a defined phase shift characteristic; and

coupling each respective comb filtered output to an input of the blending network.

5. The method of claim 4, wherein the step of applying comprises the step of:

defining the phase shift characteristic for the comb filter at zero degrees.

6. The method of claim 2, wherein the step of blending comprises the step of:

summing the processed left and right channel signals.

7. The method of claim 2, wherein the step of conditioning comprises the step of:

controlling the level of the blended signal in an amplifying circuit having an adjustable gain.

8. The method of claim 1, further comprising the steps of:

processing the left and right input channels of the stereo sound program in first and second head related transfer function (HRTF) networks for each respective channel to provide second left and right output signals; and

transmitting the second left and right output signals to respective left and right inputs to a localized speaker system configured as a headset for playback.

9. The method of claim 8, wherein the step of processing further comprises the step of:

redistributing the spectral content of each left and right input channel within the audible range of frequencies.

10. The method of claim 9, wherein the step of redistributing comprises the step of:

applying the respective signal to the input of a comb filter network having a defined phase shift characteristic.

11. The method of claim 10, wherein the step of applying comprises the step of:

defining the phase shift characteristic for the comb filter at ninety degrees.

12. The method of claim 8, wherein the step of processing comprises the step of:

providing each of the second left and right output signals from the first and second HRTF networks in the form of an unshadowed, nearest ear component signal and a shadowed, farthest ear component signal.

13. The method of claim 8, wherein the step of transmitting comprises the step of:

coupling the second left and right output signals via a wireless link.

14. The method of claim 8, wherein the step of transmitting comprises the step of:

coupling the second left and right output signals via a conducting link.

15. The method of claim 14, further comprising the steps of:

processing each left and right input channel of the stereo signal in first and second head related transfer function (HRTF) networks for each respective channel to provide second left and right output signals; and

transmitting the second left and right output signals to respective left and right inputs to a localized speaker system configured as a headset for playback.

16. The method of claim 15, wherein the step of processing further comprises the step of:

redistributing the spectral content of each left and right input channel within the audible range of frequencies.

17. The method of claim 16, wherein the step of redistributing comprises the step of:

applying the respective signal to the input of a comb filter network having a defined phase shift characteristic.

18. The method of claim 17, wherein the step of applying comprises the step of:

defining the phase shift characteristic for the comb filter at ninety degrees.

19. The method of claim 15, wherein the step of processing comprises the step of:

providing each of the second left and right output signals from the first and second HRTF networks in the form of an unshadowed, nearest ear component signal and a shadowed, farthest ear component signal.

20. The method of claim 15, wherein the step of transmitting comprises the step of:

coupling the first end second pairs of output signals via a wireless link.

21. The method of claim 15, wherein the step of transmitting comprises the step of:

coupling the first and second pairs of output signals via a conducting link.

22. The method of claim 8, wherein the step of transmitting further comprises:

placing left and right, rearward-facing loudspeakers substantially in the plane of the zygomatic arch of a listener and proximate a respective left and right ear of the listener.

23. The method of claim 1, wherein the step of producing a virtual sound source further comprises:

listening to the stereo sound program being reproduced via front left, front center and front right loudspeakers and a localized speaker system.

24. A method for enhancing the sound field image from a listening position during reproduction of multi-channel sound, comprising the steps of:

receiving left and right channels of the stereo sound program;

generating a virtual center channel signal from the left and right channels of the stereo sound program;

driving a physical center channel speaker with the virtual center channel signal;

producing a virtual sound source at a central location in a front portion of the listening space dispose between the physical center channel speaker and the listener position;

and feeding respective left and right binauralized output signals resulting from processing the left and right channels of the stereo sound program in a binauralizer to respective left and right localized loudspeakers positioned in rearward-facing orientation in the plane of the zygomatic arch proximate each respective left and right ear of a listener, such left and right binauralized output signals from the left and right localized loudspeakers in combination with the output of the center channel speaker providing the virtual sound source.

25. The method of claim 24, wherein the step of generating comprises the steps of:

processing the left and right channels of the stereo sound program in first and second networks respectively, while substantially maintaining the original overall bandwidth in each left and right channel and providing first left and right output signals each having an output level substantially corresponding to the respective original left and right channel signal levels;

blending the processed first left and right output signals to provide the virtual center channel signal; and

conditioning the virtual center channel signal for driving the center channel loudspeaker.

26. The method of claim 25, wherein the step of processing further comprises the step of:

redistributing the spectral content of each left and right input channel within the audible range of frequencies.

27. The method of claim 26, wherein the step of redistributing the spectral content of each respective channel comprises the steps of:

applying the respective signal to the input of a comb filter network having a defined phase shift characteristic; and

coupling each respective comb filtered output to an input of the blending network.

28. The method of claim 27, wherein the step of applying comprises the step of:

defining the phase shift characteristic for the comb filter at zero degrees.

29. The method of claim 25, wherein the step of blending comprises the step of:

summing the processed left and right channel signals.

30. The method of claim 25, wherein the step of conditioning comprises the step of:

controlling the level of the blended signal in an amplifying circuit having an adjustable gain.

31. The method of claim 24, wherein the step of producing a virtual sound source further comprises:

listening to the stereo sound program being reproduced via front left, front center and front right loudspeakers and a localized speaker system.