Enhancing the aural perception of speech

• US 20030216907A1
• Filed: 05/14/2002
• Published: 11/20/2003
• Est. Priority Date: 05/14/2002
• Status: Abandoned Application

• Current Assignee: Acoustic Technologies Incorporated (Cirrus Logic Incorporated)
• Original Assignee: Acoustic Technologies Incorporated (Cirrus Logic Incorporated)
• Inventors: Thomas, John D.
• Application Number:
  US10/145,315
• Publication Number:
  US 20030216907A1
• Time in Patent Office: Days
• US Class Current: 704/200.1
• CPC Class Codes: G10L 21/0264 characterised by the type of parameter measurement, e.g. correlation techniques, zero crossing techniques or predictive techniques
• CPC Class Codes: G10L 21/0364 for improving intelligibility

Abstract

An electrical signal representing speech is filtered by attenuating low frequency components of the signal. The RMS amplitude of the signal after filtering is compared with the RMS amplitude of the signal before filtering and the ratio is used to control the gain of an amplifier coupled to the filtered signal. The harmonic content of the electrical signal is increased, before or after filtering, by raising the signal to a power, filtering, raising the signal to the inverse power, and filtering. The power is preferably greater than one and less than two. The final output signal is approximately as loud as the original signal.

Claims

1. An apparatus for processing an electrical signal representing speech for enhancing the perception of speech, said apparatus comprising:

a harmonics generator having an input for receiving said electrical signal and an output, said generator increasing the harmonic content of the electrical signal;

a first filter coupled to said output and producing a filtered output signal;

a multiplier coupled to said first filter for adjusting the amplitude of the filtered output signal;

a first amplitude detector coupled to said first filter for producing a first control signal representative of said filtered output signal;

a second amplitude detector coupled to said harmonics generator for producing a second control signal; and

a divider for producing a third control signal representative of the ratio of the second control signal to the first control signal;

wherein said third control signal is coupled to said multiplier for adjusting the amplitude of the filtered output signal.

2. The apparatus as set forth in claim 1 wherein said harmonics generator increases the odd harmonics of said electrical signal.

3. The apparatus as set forth in claim 1 wherein said second amplitude detector is coupled to the output of said harmonics generator.

4. The apparatus as set forth in claim 1 wherein said second amplitude detector is coupled to the input of said harmonics generator.

5. The apparatus as set forth in claim 1 wherein said harmonics generator includes:

a first amplifier having a first exponential transfer function;

a second filter coupled to said first amplifier; and

a second amplifier having a second exponential transfer function;

wherein said first exponential transfer function is a power greater than one and less than two and said second exponential transfer function is a power greater than zero and less than one.

6. The apparatus as set forth in claim 5 wherein said harmonics generator further includes a third filter coupled to said second amplifier.

7. The apparatus as set forth in claim 6 wherein said second filter is a high shelf filter and said third filter is a low shelf filter.

8. The apparatus as set forth in claim 5 wherein said first exponential transfer function is a power ≧

1.2 and ≧

1.5.

9. The apparatus as set forth in claim 1 wherein said first filter is a high shelf filter.

10. An apparatus for increasing the harmonic content of an electrical signal, said apparatus comprising:

a first amplifier having a first transfer function, sgn(x)·

[abs(x)]^c;

a first filter coupled to said first amplifier; and

a second amplifier having a second transfer function, sgn(x)·

[abs(x)]^1/c;

wherein 1<

c<

2.

11. The apparatus as set forth in claim 10 and further including:

a second filter coupled to said second amplifier.

12. The apparatus as set forth in claim 10 wherein 1.2≦

c≦

1.5.

13. A method for processing an electrical signal representing speech for enhancing the perception of speech, said method comprising the steps of:

increasing the harmonic content of the electrical signal to produce an enhanced signal;

attenuating low frequency components of the enhanced signal to produce a filtered, enhanced signal; and

adjusting the amplitude of the filtered, enhanced signal in accordance with the ratio of the amplitudes of the unfiltered signal to the filtered signal.

14. The method as set forth in claim 13 wherein said increasing step includes the step of increasing the odd harmonic content of the electrical signal.

15. The method as set forth in claim 13 wherein said increasing step includes the steps of:

expanding the electrical signal by a power less than two to produce an augmented signal;

attenuating low frequency components of the augmented signal to produce a filtered, augmented signal; and

compressing the filtered, augmented signal by a power greater than zero and less than one.

16. The method as set forth in claim 15 wherein said increasing step further includes the step of:

attenuating high frequency components of the filtered, augmented signal to produce the enhanced signal.

17. A method for processing an electrical signal representing speech for enhancing the perception of speech, said method comprising the steps of:

attenuating low frequency components of the electrical signal to produce an enhanced signal; and

adjusting the amplitude of the enhanced signal in accordance with the ratio of the amplitudes of the electrical signal to the enhanced signal.

18. The method as set forth in claim 17 and further including the step of:

increasing the odd harmonic content of the enhanced signal to produce an output signal.

19. The method as set forth in claim 18 wherein said increasing step is the first step in the method.

20. The method as set forth in claim 18 wherein said increasing step is the last step in the method.

21. The method as set forth in claim 17 wherein said increasing step includes the steps of:

expanding the enhanced signal by a power less than two to produce an augmented signal;

attenuating low frequency components of the augmented signal to produce a filtered, augmented signal; and

compressing the filtered, augmented signal by a power greater than zero and less than one; and

attenuating high frequency components of the filtered, augmented signal to produce the output signal.