Centralizing of a spatially expanded stereophonic audio image

• US 6,711,265 B1
• Filed: 10/24/2001
• Issued: 03/23/2004
• Est. Priority Date: 05/13/1999
• Status: Expired due to Term

• Current Assignee: InterDigital Madison Patent Holdings (InterDigital, Inc.)
• Original Assignee: Thomson Licensing SA (Vantiva SA)
• Inventors: Morris, Robert Edward Jr.
• Primary Examiner(s): Harvey, Minsun Oh
• Application Number:
  US10/009,141
• Time in Patent Office: 881 Days
• Field of Search: 381/17, 381/103, 381/98, 381/99, 381/27
• US Class Current: 381/17
• CPC Class Codes: H04S 1/002 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

In a stereophonic system having sum and difference signals with expanded spatial imaging, localization of center audio materials more towards the center is accomplished by equalization of the (L+R) sum signal. The equalization comprises decreasing the bass response while increasing the treble response of the sum signal with the desired bass reduction being accomplished by the use of a gyrator to economically synthesize an inductance. Additionally, the equalizations in the (L+R) sum signal to reduce the signal at bass frequencies and to increase the signal at treble frequencies are switchable singly or in combination between “ON” and “OFF” modes.

Claims

1. A stereophonic audio system, comprising:

means for providing (L+R) and (L−

R) signals and respective signal paths;

means for providing a spatially expanded stereophonic audio effect in the (L−

R) signal, and

means for processing the (L+R) signal for concentrating the apparent location of central sounds closer to the center between left and right sound emanating loudspeakers, the means for processing comprising;

means for reducing signal levels at bass frequencies, and

means for increasing signal levels at treble frequencies,

the means for reducing signal levels at bass frequencies comprising a gyrator.

2. The audio system of claim 1 wherein the gyrator is in shunt across the (L+R) signal path.

3. The audio system of claim 1 wherein the means for increasing signal levels at treble frequencies comprises a high pass filter in series with the (L+R) signal path.

4. The audio system of claim 1 wherein the bass signal reduction includes frequencies within the band of 100 Hz to 580 Hz.

5. The audio system of claim 1 wherein the treble signal increase includes frequencies above 580 Hz.

6. The audio system of claim 1 wherein the reduction of signal levels at bass frequencies and the increase of signal levels at treble frequencies are switchable singly or in combination between “

ON” and

“

OFF”

modes.

7. The audio system of claim 6 wherein the switching is responsive to control signals.

8. The audio system of claim 7 wherein the control signals are provided by a microprocessor.

9. A stereophonic audio system, comprising:

means for providing (L+R) and (L−

R) signals and respective signal paths;

means for providing a spatially expanded stereophonic audio effect in the (L−

R) signal, and

means for processing the (L+R) signal for concentrating the apparent location of central sounds closer to the center between left and right sound emanating loudspeakers, the means for processing comprising;

means for reducing signal levels at bass frequencies, and

means for increasing signal levels at treble frequencies,

the means for reducing signal levels at bass frequencies and the means for increasing signal levels at treble frequencies being switchable singly or in combination between “

ON” and

“

OFF”

modes.

10. The audio system of claim 9 wherein the switching is responsive to control signals.

11. The audio system of claim 10 wherein the control signals are provided by a microprocessor.

12. A stereophonic audio system, comprising:

means for providing (L+R) and (L−

R) signals and respective signal paths;

means for providing a spatially expanded stereophonic audio effect in the (L−

R) signal, and

means for processing the (L+R) signal for concentrating the apparent location of central sounds closer to the center between left and right sound emanating loudspeakers, the means for processing comprising;

means for reducing signal levels at bass frequencies, and

means for increasing signal levels at treble frequencies,

the means for reducing signal levels at bass frequencies comprising a gyrator,

the reduction signal levels at bass frequencies and the increase signal levels at treble frequencies are switchable singly or in combination between “

ON” and

“

OFF”

modes.

13. The audio system of claim 12 wherein the gyrator is in shunt across the (L+R) signal path.

14. The audio system of claim 12 wherein the means for increasing signal levels at treble frequencies comprises a high pass filter in series with the (L+R) signal path.

16. The audio system of claim 12 wherein the treble signal increase includes frequencies above 580 Hz.

17. The audio system of claim 12 wherein the switching is responsive to control signals.

18. The audio system of claim 17 wherein the control signals are provided by a microprocessor.

15. The bass signal reduction includes frequencies within the band of 100 Hz to 580 Hz.