System and method for improving clarity of audio systems

• US 6,335,973 B1
• Filed: 10/23/1997
• Issued: 01/01/2002
• Est. Priority Date: 01/11/1996
• Status: Expired due to Term

• Current Assignee: Qwest Communications International Incorporated (Lumen Technologies, Inc.)
• Original Assignee: Qwest Communications International Incorporated (Lumen Technologies, Inc.)
• Inventors: Case, Eliot M.
• Primary Examiner(s): Isen, Forester W.
• Assistant Examiner(s): PENDLETON, BRIAN T
• Application Number:
  US08/956,677
• Time in Patent Office: 1,531 Days
• Field of Search: 381/61, 381/98, 381/103, 846/98
• US Class Current: 381/61
• CPC Class Codes: H03G 9/025 frequency-dependent volume compression or expansion, e.g. multiple-band systems H03G9/10, H03G9/18 take precedence

Abstract

A system and method for improving clarity of an audio signal selects frequencies of the audio signal for processing and adds even harmonic distortion to the selected frequencies, preferably, of at least the second order. The system and method are particularly suited for hearing aid, voice messaging, and telephony applications. In addition, the system and method may be applied to other very low bandwidth signals, such as data compressed audio signals, computer voice files, computer audio files, and numerous other technologies which have an audio response less than normal human perception. The technique also applies to the use of perceptually coded audio.

Claims

1. A method for improving clarity of an input signal for a hearing aid, the method comprising:

selecting frequencies of the input signal for processing; and

adding even harmonic distortion to the selected frequencies by applying a nonlinear transfer function having a ratio of positive half-cycle gain to a negative half-cycle gain greater than unity.

2. The method of claim 1 wherein:

the even harmonic distortion added to the selected frequencies is of at least the second order.

3. The method of claim 1 wherein adding comprises:

applying a nonlinear transfer function having a unity gain for positive half-cycles and a gain less than unity for negative half-cycles.

4. The method of claim 3 wherein:

the nonlinear transfer function has a variable negative half cycle gain.

5. The method of claim 1 wherein selecting comprises:

attenuating a portion of the frequencies of the input signal by applying a gain less than unity so as to deselect that portion.

6. The method of claim 1 wherein selecting comprises:

amplifying a portion of the frequencies of the input signal by applying a gain greater than unity so as to select that portion.

7. A method for improving clarity of an audio signal for a phone switch, the method comprising:

selecting frequencies of the audio signal for processing; and

adding even harmonic distortion to the selected frequencies by applying a nonlinear transfer function having a ratio of positive half-cycle gain to negative half-cycle gain greater than unity.

8. The method of claim 7 wherein:

the even harmonic distortion added to the selected frequencies is of at least the second order.

9. The method of claim 7 wherein:

the phone switch is a central office telephone switch.

10. The method of claim 7 wherein:

the phone switch is a cellular phone switch.

11. The method of claim 7 wherein adding comprises:

applying a nonlinear transfer function having a unity gain for positive half-cycles and a gain less than unity for negative half-cycles.

12. The method of claim 11 wherein:

the nonlinear transfer function has a variable negative half cycle gain.

13. A method of improving clarity of an audio signal for a voice messaging system, the method comprising:

selecting frequencies of the audio signal for processing; and

adding even harmonic distortion to the selected frequencies by applying a nonlinear transfer function having a ratio of positive half-cycle gain to negative half-cycle gain greater than unity.

14. The method of claim 13 wherein:

the even harmonic distortion added to the selected frequencies is of at least the second order.

15. The method of claim 13 wherein adding comprises:

applying a nonlinear transfer function having a unity gain for positive half-cycles and a gain less than unity for negative half-cycles.

16. The method of claim 15 wherein:

the nonlinear transfer function has a variable negative half cycle gain.