Audio signal processing

• US 7,164,768 B2
• Filed: 06/21/2001
• Issued: 01/16/2007
• Est. Priority Date: 06/21/2001
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Aylward, J. Richard, Anderson, Erik E.
• Primary Examiner(s): PENDLETON, BRIAN T
• Application Number:
  US09/886,868
• Publication Number:
  US 20030002693A1
• Time in Patent Office: 2,035 Days
• Field of Search: 381/300, 381/307, 381/22, 381/18, 381/19, 381/20, 381/17, 381/21, 381/23
• US Class Current: 381/22
• CPC Class Codes: H04S 3/00 Systems employing more than two channels, e.g. quadraphonic H04S5/00, H04S7/00 take precedence

Abstract

A method for processing and transducing audio signals. An audio system has a first audio signal and a second audio signal that have amplitudes. A method for processing the audio signals includes dividing the first audio signal into a first spectral band signal and a second spectral band signal; scaling the first spectral band signal by a first scaling factor proportional to the amplitude of the second audio signal; and scaling the first spectral band signal by a second scaling factor to create a second signal portion. Other portions of the disclosure include application of the signal processing method to multichannel audio systems, and to audio systems having different combinations of directional loudspeakers, full range loudspeakers, and limited range loudspeakers.

Claims

1. In an audio system having a first audio signal and a second audio signal, said first and second audio signals having amplitudes, a method for processing audio signals comprising:

dividing said first audio signal into a first spectral band signal and a second spectral band signal

scaling said first spectral band signal by a first scaling factor related to the amplitude of said first audio signal to create a first signal portion,

scaling said first spectral band signal by a second scaling factor related to the amplitude of said second audio signal to create a second signal portion,

adjusting said first and second scaling factors to create an apparent source of sound that is a selected one of forward and rearward,

filtering said first signal portion by a first filter to produce a filtered first signal portion, and

filtering said second signal portion by a second filter to produce a filtered second signal portion.

2. A method for processing audio signals in accordance with claim 1, wherein said first and second audio signals are associated with directional channels in a multichannel audio system.

3. A method for processing audio signals in accordance with claim 2, wherein

$\frac{\mathrm{SF1}}{\mathrm{SF2}}=\frac{\mathrm{ampl2}}{\mathrm{ampl1}},$

wherein SF1 is said first scaling factor, SF2 is said second scaling factor, ampl1 is said amplitude of said first audio signal and ampl2 is said amplitude of said second audio signal.

4. A method for processing audio signals in accordance with claim 3, wherein said first filter and said second filter include a filter portion having a frequency response and time delay effect similar to that of the human head.

5. A method for processing audio signals in accordance with claim 1, wherein said first filter and said second filter include a filter portion having a frequency response and time delay effect similar to that of the human head.

6. A method for processing audio signals in accordance with claim 5, wherein one of said first filter or said second filter has filter portion having a frequency response and time delay effect similar to frequency response and time delay effect of the human head on a sound wave arriving from the front of said human head and the other of said first filter or second filter has filter portion having a frequency response and time delay effect similar to frequency response and time delay effect of the human head on a sound wave arriving from the rear of said human head.

7. A method for processing audio signals in accordance with claim 5, wherein said first filter and said second filter have a filter portion having frequency response and time delay effect similar to frequency response and time delay effect of the human head on a sound wave arriving from the front of said human head.

8. A method for processing audio signals in accordance with claim 5, wherein said first filter and said second filter have a filter portion having a frequency response and time delay effect similar to frequency response and time delay effect of the human head on a sound wave arriving from the rear of said human head.

9. A method for processing audio signals in accordance with claim 5, wherein said first filter and said second filter include a filter portion having a frequency response and time delay effect inverse to said filter having a frequency response and time delay effect similar to the human head.

10. In an audio system having a first audio signal and a second audio signal, said first and second audio signals having amplitudes, a method for processing said audio signals comprising,

dividing said first audio signal into a first spectral band signal and a second spectral band signal;

scaling said first spectral band signal by a first scaling factor related to the amplitude of said first audio signal to create a first signal portion,

scaling said first spectral band signal by a second scaling factor related to the amplitude of said second audio signal to create a second signal portion,

adjusting said first and second scaling factors to create an apparent source of sound that is a selected one of being forward and rearward,

filtering said first signal portion by a first filter to produce a filtered first signal portion, and

filtering said second signal portion by a second filter to produce a filtered second signal portion,

wherein one of said first filter and said second filter has a flat frequency response.

11. A method for processing audio signals in accordance with claim 10, wherein the other of said first filter and said second filter has a flat frequency response.

12. A method for processing first and second audio signals having first and second amplitudes respectively, comprising,

dividing said first audio signal into a first spectral band signal and a second spectral band signal;

scaling said first spectral band signal by a first scaling factor related to the amplitude of said first audio signal to create a first signal portion,

scaling said first spectral band signal by a second scaling factor related to the amplitude of said second audio signal to create a second signal portion,

adjusting said first and second scaling factors to create an appearance source of sound that is a selected one of being forward and rearward,

wherein said first and second audio signals are associated with directional channels in a multichannel audio system,

filtering said first signal portion by a first filter to produce a filtered first signal portion,

filtering said second signal portion by a second filter to produce a filtered second signal portion,

wherein

$\frac{\mathrm{SF}<br><br><br><br>1}{\mathrm{SF}<br><br><br><br>2}=\frac{\mathrm{ampl}<br><br><br><br>2}{\mathrm{ampl}<br><br><br><br>1},$

wherein SF1 is said first scaling factor, SF2 is said second scaling factor, ampl1 is said amplitude of said first audio signal and ampl2 is said amplitude of said second audio signal, and

combining said filtered first signal portion, said filtered second signal portion and said second spectral band signal.

13. A method for processing audio signals comprising,

dividing said first audio signal into a first spectral band signal and a second spectral band signal;

scaling said first spectral band signal by a first scaling factor related to the amplitude of said first audio signal to create a first signal portion,

scaling said first spectral band signal by a second scaling factor related to the amplitude of said second audio signal to create a second signal portion,

adjusting said first and second scaling factors to create an apparent source of sound that is a selected one of being forward and rearward,

wherein said first and second audio signals are associated with directional channels in a multichannel audio system,

filtering said first signal portion by a first filter to produce a filtered first signal portion,

filtering said second signal portion by a second filter to produce a filtered second signal portion, and

combining said filtered second signal portion with said second spectral band signal.

14. A method for processing first and second audio signals having first and second amplitudes respectively comprising,

dividing said first audio signal into a first spectral band signal and a second spectral band signal;

scaling said first spectral band signal by a first scaling factor related to the amplitude of said first audio signal to create a first signal portion,

scaling said first spectral band signal by a second scaling factor related to the amplitude of said second audio signal to create a second signal portion,

adjusting said first and second scaling factors to create an apparent source of sound that is a selected one of being forward and rearward,

wherein said first and second audio signals are associated with directional channels in a multichannel audio system,

filtering said first signal portion by a first filter to produce a filtered first signal portion,

filtering said second signal portion by a second filter to produce a filtered second signal portion, and

combining said filtered first signal portion, said filtered second signal portion and said second spectral band signal.

15. In an audio system having a first audio signal and a second audio signal, said first and second audio signals having amplitudes, a method for processing audio signals comprising:

dividing said first audio signal into a first spectral band signal and a second spectral band signal

scaling said first spectral band signal by a first scaling factor related to the amplitude of said first audio signal to create a first signal portion,

scaling said first spectral band signal by a second scaling factor related to the amplitude of said second audio signal to create a second signal portion, and

adjusting said first and second scaling factors to create an apparent source of sound that is a selected one of being forward and rearward,

wherein

$\frac{\mathrm{SF}<br><br><br><br>1}{\mathrm{SF}<br><br><br><br>2}=\frac{\mathrm{ampl}<br><br><br><br>2}{\mathrm{ampl}<br><br><br><br>1},$

wherein SF1 is said first scaling factor, SF2 is said second scaling factor, ampl1 is said amplitude of said first audio signal and ampl2 is said amplitude of said second audio signal.

16. In an audio system having a first audio signal and a second audio signal, said first and second audio signals having amplitudes, a method for processing said audio signals comprising,

dividing said first audio signal into a first spectral band signal and a second spectral band signal;

scaling said first spectral band signal by a first scaling factor related to the amplitude of said first audio signal to create a first signal portion,

scaling said first spectral band signal by a second scaling factor related to the amplitude of said second audio signal to create a second signal portion,

adjusting said first and second scaling factors to create an apparent source of sound that is a selected one of being forward and rearward,

filtering said first signal portion by a first filter to produce a filtered first signal portion,

filtering said second signal portion by a second filter to produce a filtered second signal portion, and

combining said filtered first signal portion with said second audio signal to produce a first combined signal.

17. A method for processing audio signals in accordance with claim 16, with an audio system including a directional loudspeaker unit, said combining further including combining said second spectral band signal and said filtered second signal portion so that said first combined signal includes said filtered first signal portion, said filtered second signal portion, said second spectral band signal, and said second audio signal and further comprising,

electroacoustically transducing, by said directional loudspeaker unit, said first combined signal.

18. In an audio system having a first audio signal and a second audio signal, said first and second audio signals having amplitudes, a method for processing audio signals comprising:

dividing said first audio signal into a first spectral band signal and a second spectral band signal

scaling said first spectral band signal by a first scaling factor related to the amplitude of said first audio signal to create a first signal portion,

scaling said first spectral band signal by a second scaling factor related to the amplitude of said second audio signal to create a second signal portion, and

adjusting said first and second scaling factors to create an apparent source of sound that is a selected one of being forward and rearward,

wherein the sum of said first scaling factor and said second scaling factor is one.

19. In an audio system having a plurality of directional channels, a first audio signal and a second audio signal, said first and second audio signals representing adjacent directional channels on the same lateral side of a listener in a normal listening position, a method for processing audio signals further comprising:

a method for processing said audio signals, comprising,

dividing said first audio signal into a first spectral band signal and a second spectral band signal;

scaling said first spectral band signal by a first time varying calculated scaling factor related to the amplitude of said first audio signal to create a first signal portion;

scaling said first spectral band signal by a second time varying calculated scaling factor related to the amplitude of said second audio signal to create a second signal portion,

adjusting said first and second scaling factors to make the apparent source of sound one of forward and rearward of said normal listening position,

filtering said first signal portion by a first filter to produce a filtered first signal portion, and

filtering said second signal portion by a second filter to produce a filtered second signal portion.

20. A method for processing first and second audio signals representing adjacent directional channels on the same lateral side of a listener in a normal listening position comprising,

dividing said first audio signal into a first spectral band signal and a second spectral band signal;

scaling said first spectral band signal by a first time varying calculated scaling factor related to the amplitude of said first audio signal to create a first signal portion; and

scaling said first spectral band signal by a second time varying calculated scaling factor related to the amplitude of said second audio signal to create a second signal portion,

filtering said first signal portion by a first filter to produce a filtered first signal portion,

filtering said second signal portion by a second filter to produce a filtered second signal portion, and

combining said filtered first signal portion with said second audio signal to produce a first combined signal.

21. A method for processing audio signals in accordance with claim 20 with an audio system including a directional loudspeaker unit, said combining further including combining said second spectral band signal and said filtered second signal portion so that said first combined signal includes said filtered first signal portion, said filtered second signal portion, said second spectral band signal, and said second audio signal, said method further comprising,

electroacoustically transducing, by said directional loudspeaker unit, said first combined signal.

22. In an audio system having a first audio signal and a second audio signal, said first and second audio signals having amplitudes, a method for processing audio signals comprising

dividing said first audio signal into a first spectral band signal and a second spectral band signal

scaling said first spectral band signal by a first scaling factor related to the amplitude of said first audio signal to create a first signal portion,

scaling said first spectral band signal by a second scaling factor related to the amplitude of said second audio signal to create a second signal portion,

adjusting said first and second scaling factors to create an apparent source of sound that is a selected one of being forward and rearward, and

time delaying said first spectral band signal relative to said second spectral band signal.

23. A method for processing first and second audio signals having first and second amplitudes respectively comprising,

dividing said first audio signal into a first spectral band signal and a second spectral band signal;

scaling said first spectral band signal by a first scaling factor related to the amplitude of said first audio signal to create a first signal portion,

scaling said first spectral band signal by a second scaling factor related to the amplitude of said second audio signal to create a second signal portion,

adjusting said first and second scaling factors to create an apparent source of sound that is a selected one of being forward and rearward,

wherein said first and second audio signals are associated with directional channels in a multichannel audio system,

filtering said first signal portion by a first filter to produce a filtered first signal portion,

filtering said second signal portion by a second filter to produce a filtered second signal portion,

wherein

$\frac{\mathrm{SF1}}{\mathrm{SF2}}=\frac{\mathrm{ampl2}}{\mathrm{ampl1}},$

wherein SF1 is said first scaling factor, SF2 is said second scaling factor, ampl1 is said amplitude of said first audio signal and ampl2 is said amplitude of said second audio signal, and

combining said filtered second signal portion with said second spectral band signal.