Hearing compensation system incorporating signal processing techniques

• US 20050111683A1
• Filed: 09/08/2004
• Published: 05/26/2005
• Est. Priority Date: 07/08/1994
• Status: Active Grant

• Current Assignee: Brigham Young University (The Church of Jesus Christ of Latter-Day Saints)
• Original Assignee: Brigham Young University An Educational Institution Corporation of Utah
• Inventors: Christiansen, Richard Wesley, Chabries, Douglas Melvin
• Granted Patent: US 8,085,959 B2
• Time in Patent Office: Days
• US Class Current: 381/317
• CPC Class Codes: H03G 9/005 of digital or coded signals
• CPC Class Codes: H03G 9/025 frequency-dependent volume compression or expansion, e.g. multiple-band systems H03G9/10, H03G9/18 take precedence
• CPC Class Codes: H04R 2430/03 Synergistic effects of band splitting and sub-band processing
• CPC Class Codes: H04R 25/356 Amplitude, e.g. amplitude shift or compression

Abstract

A hearing compensation system comprises a plurality of bandpass filters having an input connected to an input transducer and each bandpass filter having an output connected to the input of one of a plurality of multiplicative automatic gain control (MAGC) circuits whose outputs are summed together and connected to the input of an output transducer. The MAGC circuits attenuate acoustic signals having a constant background level without the loss of speech intelligibility. The identification of the background noise portion of the acoustic signal is made by the constancy of the envelope of the input signal in each of the several frequency bands. The background noise that will be suppressed includes multi-talker speech babble, fan noise, feedback whistle, florescent light hum, and white noise. For use in the consumer electronics field background acoustic noise may be sensed and used to adjust gain in the various MAGC circuits so as to improve a user'"'"'s listening experience, whether the user is hearing impaired or not.

Claims

1. A noise compensation system, comprising:

a first circuit node receiving an electronic signal representative of an original audio signal;

a plurality, n, of channels each including a bandpass filter and a multiplicative automatic gain control (MAGC) circuit, each of said plurality of channels arranged so that an input of the bandpass filter is coupled to the first circuit node, an output of the bandpass filter is coupled to an output of the MAGC and an output of the MAGC is coupled to an output node, each of the n MAGC circuits having a transfer function responsive to a value, K_n, and each bandpass filter selecting for its corresponding channel a certain range of audio frequencies of said electronic signal;

an acoustic input transducer receiving an ambient acoustic noise signal and converting it to an ambient noise electronic signal; and

an ambient noise measurement circuit receiving the ambient noise electronic signal and providing an output K_n to each of the n MAGC circuits.

2. The system of claim 1, wherein said ambient noise measurement circuit further comprises:

a plurality of channels each including a bandpass filter, an ambient noise estimator circuit and a gain calculator, wherein;

each bandpass filter is arranged so that an input of the bandpass filter is coupled to receive the ambient noise electronic signal and the bandpass filter selects a predetermined frequency range of the ambient noise electronic signal to provide to a corresponding ambient noise estimator circuit, and

each ambient noise estimator circuit is coupled to a gain calculator to provide a value K_n for input to a corresponding one of the n MAGC circuits.

3. The system of claim 2, wherein said ambient noise estimator circuit includes an absolute value processor block and a bandpass filter processor block.

4. A noise compensation system, comprising:

a first circuit node coupled to receive a first electronic signal representative of a relatively noise free original audio signal;

a plurality, n, of first channels, each of said n first channels corresponding to a predetermined audio frequency range and each of said n first channels disposed between said first circuit node and a second circuit node and wherein;

each of said n first channels includes a bandpass filter having an input coupled to said first circuit node and adapted to select a predetermined audio frequency range of signals and provide a bandpass-filtered signal to an input of a corresponding multiplicative automatic gain control (MAGC) circuit,

each of said n MAGC circuits has a transfer function responsive to a value K_n; and

each of said n MAGC circuits has an output coupled to said second circuit node;

an audio input transducer adapted to receive an ambient acoustic noise signal and convert it to an ambient noise electronic signal; and

an ambient noise measurement circuit receiving the ambient noise electronic signal and providing n K_n values to said corresponding n MAGC circuits.

5. The system of claim 4 further comprising an acoustic output transducer coupled to said second circuit node.

6. The system of claim 4 wherein:

said ambient noise measurement circuit includes a plurality, n, of second channels, each of said n second channels corresponding to the n^th audio frequency range of said first channels;

each of said n second channels includes a bandpass filter having an input coupled to said first circuit node and adapted to select a predetermined audio frequency range of signals, so as to provide a bandpass-filtered signal to an input of a corresponding ambient noise estimator circuit.

7. The noise compensation system of claim 4 wherein said ambient noise estimator circuits include outputs coupled to respective gain calculators and said gain calculators output K_n values to said respective n MAGC circuits.

8. A noise compensation system comprising:

a first circuit node receiving an electronic signal representative of an original audio signal;

a first switch having a first input, a second input and a common node, said first input coupled to said first circuit node, said second input coupled to an acoustic input transducer arranged to detect ambient acoustic noise and convert it to an ambient noise electrical signal, and said common node coupled to a second circuit node;

a plurality, n, of bandpass filters having inputs coupled to said second circuit node and outputs coupled to common nodes of n corresponding second switches, said switches each having one common node and a first output and a second output;

said first switch and said n second switches switchable between a first state in which said first switch couples said first switch common node to said first circuit node and said n second switches couple said second switch common nodes respectively to n separate multiplicative automatic gain control (MAGC) circuits, and a second state in which said first switch couples said first switch common node to said acoustic input transducer and said n second switches couple said second switch common nodes respectively to n separate acoustic noise estimator (ANE) circuits, in turn coupled to n corresponding gain calculation (GC) circuits which provide n respective K_n outputs to said corresponding MAGC circuits; and

a summing junction combining the outputs of said n MAGC circuits.

9. The system of claim 8, further comprising:

an acoustic output transducer coupled to said summing junction.

10. An audio output device, comprising:

an acoustic input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to receive said electrical signals, each of said audio bandpass filters having an output; and

a plurality of multiplicative automatic gain control (MAGC) circuits coupled to a respective output of one of said plurality of audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise suppression circuit;

wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise suppression circuit.

11. The device of claim 10, further comprising:

an acoustic output transducer responsive to said plurality of MAGC circuits.

12. The device of claim 10, wherein said noise suppression circuit comprises a bandpass filter.

13. The audio output device of claim 12, wherein said bandpass filter is configured to have a single pole at a minimum frequency and a single zero at a cutoff frequency.

14. The audio output device of claim 10, wherein:

said hearing compensation circuit comprises a high pass filter and a low pass filter;

an output of said low pass filter is coupled to an amplifier having amplifier constant K and having an amplifier output; and

said amplifier output and an output of said hearing compensation circuit are summed together.

15. An audio output device, comprising:

an input transducer for converting input acoustical energy into output electrical energy corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to the output of said input transducer;

a plurality of multiplicative automatic gain control (MAGC) circuits, each of said MAGC circuits coupled to an output of one of said audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise estimation circuit; and

an output transducer responsive to said plurality of MAGC circuits,

wherein noise present in the acoustical energy is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

16. The audio output device of claim 15, wherein an acoustic signal having an approximately constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

17. An audio output device, comprising,

an input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to the output of said input transducer;

a plurality of multiplicative automatic gain control (MAGC) circuits, each of said MAGC circuits coupled to an output of one of said audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise estimation circuit; and

an output transducer responsive to said plurality of MAGC circuits,

wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

18. A hearing aid device, comprising:

an input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to receive said output electrical signals, each of said audio bandpass filters having an output;

a plurality of multiplicative automatic gain control (MAGC) circuits, each of said MAGC circuits coupled to an output of one of said plurality of audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise suppression circuit; and

an output transducer responsive to said plurality of multiplicative automatic gain control (AGC) circuits,

wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise suppression circuit.

19. The hearing aid device of claim 18, wherein said noise suppression circuit comprises a bandpass filter.

20. The hearing aid device of claim 19, wherein said bandpass filter is configured to have a single pole at a minimum frequency and a single zero at a cutoff frequency.

21. The hearing aid device of claim 18, wherein:

said hearing compensation circuit comprises a high pass filter and a low pass filter;

an output of said low pass filter is coupled to an amplifier having amplifier constant K and having an amplifier output; and

said amplifier output and an output of said hearing compensation circuit are summed together.

22. A hearing aid device, comprising:

an input transducer for converting input acoustical energy into output electrical energy corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to the output of said input transducer;

a plurality of multiplicative automatic gain control (MAGC) circuits, each of said MAGC circuits coupled to an output of one of said audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise estimation circuit; and

an output transducer responsive to said plurality of MAGC circuits,

wherein noise present in the acoustical energy is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

23. The hearing aid device of claim 22, wherein an acoustic signal having an approximately constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

24. A hearing aid output device, comprising,

an input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy;

a plurality of hearing aid bandpass filters coupled to the output of said input transducer;

a plurality of multiplicative automatic gain control (MAGC) circuits, each of said MAGC circuits coupled to an output of one of said hearing aid bandbass filters, at least one of said AGC circuits including a hearing compensation circuit and a noise estimation circuit; and

an output transducer responsive to said plurality of MAGC circuits,

wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

25. An audio output device, comprising:

an input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy;

a multiplicative automatic gain control (MAGC) circuit coupled to said input transducer, said MAGC circuit including a high pass filter having an output, a low pass filter having an output, the output of said low pass filter being amplified by a factor of K, and a noise suppression circuit having an output; and

an output transducer responsive to said plurality of MAGC circuits,

wherein the amplified output of said low pass filter and the output of the noise suppression circuit are linearly combined to produce a first signal, the output of said high pass filter is linearly combined with the first signal; and

an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said high pass filter, said low pass filter and said noise suppression circuit.

26. The audio output device of claim 25, wherein said noise suppression circuit comprises a bandpass filter.

27. The audio output device of claim 26, wherein said bandpass filter is configured to have a single pole at a minimum frequency and a single zero at a cutoff frequency.

28. An audio output device, comprising:

an input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to receive said electrical signals, each of said audio bandpass filters having an output;

a plurality of multiplicative automatic gain control (MAGC) circuits each having at least one input and at least one output, an input of each of said MAGC circuits coupled to an output of one of said plurality of audio bandpass filters, at least one of said MAGC circuits comprising a hearing compensation circuit and a noise suppression circuit; and

an output transducer responsive to said outputs of said plurality of MAGC circuits;

wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise suppression circuit.

29. The audio output device of claim 28, wherein:

said hearing compensation circuit comprises a high pass filter and a low pass filter;

an output of said low pass filter is coupled to an amplifier having amplifier constant K and having an amplifier output; and

said amplifier output and an output of said hearing compensation circuit are summed together.

30. The audio output device of claim 28, wherein said MAGC circuits include:

a first circuit to obtain an input envelope amplitude from the coupled acoustical bandpass filter output;

a second circuit responsive to the input envelope amplitude to provide a logarithm of the input envelope amplitude;

a noise estimation circuit for obtaining an estimate of noise; and

a subtraction circuit to subtract the estimate of noise from the logarithm of the input envelope amplitude.

31. The audio output device of claim 28 wherein the electrical signals are attenuated and added to said outputs of the MAGC circuits.

32. The audio output device of claim 28, wherein the MAGC circuits have the ability to provide one gain function for noise and another gain function for desired signals.

33. The audio output device of claim 28, wherein the MAGC circuits may utilize a selected one of the gain functions of:

expansion, compression, and saturation.

34. The audio output device of claim 28, wherein the MAGC circuits may utilize selected ones of the gain functions of expansion, compression, and saturation.

35. The audio output device of claim 30, wherein the MAGC circuits provide a maximum limit to the gain.

36. The audio output device of claim 35, wherein the maximum amount of attenuation is set to an amount that results in a minimum gain and the MAGC circuits provide a maximum limit to gain.

37. The audio output device of claim 28, wherein the bandpass filter is implemented with bandpass filters having increasing bandwidth as the center frequency of the bandpass filter increases.

38. The audio output device of claim 28, wherein the bandpass filters are implemented so that all the bandpass filters have the same bandwidth.

39. An audio output device, comprising:

an input transducer for converting input acoustical energy into output electrical energy corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to the output of said input transducer;

a plurality of multiplicative automatic gain control (MAGC) circuits, each having at least one input and at least one output, an input of each of said MAGC circuits coupled to an output of one of said audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise estimation circuit; and

an output transducer responsive to said plurality of MAGC circuits,

wherein noise present in the acoustical energy is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

40. The audio output device of claim 39, wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

41. An audio output device, comprising:

an input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to the output of said input transducer;

a plurality of multiplicative automatic gain control (MAGC) circuits, each having at least one input and at least one output, an input of each of said MAGC circuits coupled to an output of one of said audio bandpass filters, at least one of said AGC circuits including a hearing compensation circuit and a noise estimation circuit;

an output transducer responsive to said plurality of multiplicative AGC circuits,

wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

42. A hearing aid device comprising:

an input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to receive said electrical signals, each of said audio bandpass filters having an output;

a plurality of multiplicative automatic gain control (MAGC) circuits each having at least one input and at least one output, an input of each of said MAGC circuits coupled to an output of one of said plurality of audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise suppression circuit; and

an output transducer responsive to said outputs of said plurality of (MAGC) circuits;

wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise suppression circuit.

43. The hearing aid device of claim 42, wherein:

said hearing compensation circuit comprises a high pass filter and a low pass filter;

an output of said low pass filter is coupled to an amplifier having an amplifier gain of K and having an amplifier output; and

said amplifier output and an output of said hearing compensation circuit are summed together.

46. The hearing aid device of claim 42, wherein the MAGC circuits include:

a first circuit to obtain an input envelope amplitude from the coupled acoustical bandpass filter output;

a second circuit responsive to the input envelope amplitude to provide a logarithm of the input envelope amplitude;

a hearing compensation circuit;

a noise estimation circuit for obtaining an estimate of noise; and

a subtraction circuit to subtract the estimate of noise from the logarithm of the input envelope amplitude.

47. The hearing aid device of claim 42, wherein the electrical signals are attenuated and added to said outputs of the MAGC circuits.

48. The hearing aid device for claim 42, wherein the MAGC circuits have the ability to provide one gain function for noise and another gain function for desired signals.

49. The hearing aid device of claim 42, wherein the MAGC circuits may utilize a selected one of the gain functions of:

expansion, compression, and saturation.

50. The hearing aid device of claim 42, wherein the MAGC circuits may utilize selected ones of the gain functions of:

expansion, compression, and saturation.

51. The hearing aid device of claim 46, wherein the MAGC circuits provide a maximum limit to the gain.

52. The hearing aid device of claim 42, wherein the bandpass filter is implemented with bandpass filters having increasing bandwidth as the center frequency of the bandpass filter increases.

53. The hearing aid device of claim 42, wherein the bandpass filters are implemented so that all the bandpass filters have the same bandwidth.

44. A hearing aid device comprising:

an input transducer for converting input acoustical energy into output electrical energy corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to the output of said input transducer;

a plurality of multiplicative automatic gain control (MAGC) circuits, each having at least one input and at least one output, an input of each of said MAGC circuits coupled to an output of one of said audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise estimation circuit; and

an output transducer responsive to output of said plurality of MAGC circuits,

wherein noise present in the acoustical energy is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

45. The hearing aid device of claim 44, wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

54. A hearing aid device comprising:

an input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to the output of said input transducer;

a plurality of multiplicative automatic gain control (MAGC) circuits, each having at least one input and at least one output, an input of each of said MAGC circuits coupled to an output of one of said audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise estimation circuit;

an output transducer responsive to said plurality of MAGC circuits,

wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

55. An audio output device comprising:

an input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy, thereby measuring the ambient acoustic sound intensity level;

a plurality of audio bandpass filters coupled to receive the output of an electronic device having an audio output, each of said audio bandpass filters having an output;

a plurality of multiplicative automatic gain control (MAGC) circuits, each having at least one input and at least one output, an input of each of said MAGC circuits coupled to an output of one of said plurality of audio bandpass filters, at least one of said MAGC circuits including;

a means for adjusting a gain of the MAGC circuit(s) to provide a boost to signals corresponding to soft sound levels present in the input acoustical energy while preserving the intensities signals corresponding to the loudest sounds present in the input acoustical energy; and

an output transducer responsive to said plurality of MAGC circuits.

56. The audio output device of claim 55, wherein:

said MAGC circuits have a hearing compensation circuit that comprises a high pass filter and a low pass filter;

the output of said low pass filter is coupled to an amplifier having an amplifier gain of K and having an amplifier output; and

said amplifier output and an output of said hearing compensation circuit are summed together.

57. The audio output device of claim 55, wherein the bandpass filter is implemented with bandpass filters having increasing bandwidth as the center frequency of the bandpass filter increases.

58. The audio output device of claim 55, wherein the bandpass filters are implemented so that all the bandpass filters have the same bandwidth.

59. The audio output device of claim 55, wherein the user is able to manually adjust the gain provided to an output intensity level corresponding to the softest sound levels present in the input acoustical energy.

60. The audio output device of claim 55, wherein the gain of the MAGC circuits are held constant for all output levels above an upper comfort level.

61. The audio output device of claim 55, wherein the gain of the MAGC circuits is negative for all output levels above an upper comfort level.

62. An audio output device, comprising:

an input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to receive said electrical signals, each of said audio bandpass filters having an output;

a plurality of multiplicative automatic gain control (MAGC) circuits, each having at least one input and at least one output, an input of each of said MAGC circuits coupled to an output of one of said plurality of audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise suppression circuit; and

an output transducer responsive to said plurality of MAGC circuits.

wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise suppression circuit.

63. The audio output device of claim 62, wherein:

said hearing compensation circuit comprises a high pass filter and a low pass filter;

an output of said low pass filter is coupled to an amplifier having an amplifier gain of K and having an amplifier output; and

said amplifier output and an output of said hearing compensation circuit are summed together.

64. An audio output device comprising:

an input transducer for converting input acoustical energy into output electrical energy corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to the output of said input transducer;

a plurality of multiplicative automatic gain control (MAGC) circuits, each having at least one input and at least one output, an input of each of said MAGC circuits coupled to an output of one of said audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise estimation circuit; and

an output transducer responsive to said plurality of MAGC circuits,

wherein noise present in the acoustical energy is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

65. The audio output device of claim 64, wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

73. The audio output device of claim 64, wherein the maximum amount of attenuation is set to an amount that results in a minimum gain and the MAGC circuits provide a maximum limit to gain.

86. The hearing aid device of claim 73, wherein the MAGC circuits provide a maximum limit to the gain.

66. An audio output device comprising:

an input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to the output of said input transducer;

a plurality of multiplicative automatic gain control (MAGC) circuits, each having at least one input and at least one output, an input of each of said MAGC circuits coupled to an output of one of said audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise estimation circuit;

an output transducer responsive to said plurality of MAGC circuits,

wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

67. The audio output device of claim 66, wherein the MAGC circuits include:

a first circuit to obtain an input envelope amplitude from the coupled acoustical bandpass filter output;

a second circuit responsive to the input envelope amplitude to provide the logarithm of the input envelope amplitude;

a noise estimation circuit for obtaining an estimate of noise; and

a subtraction circuit to subtract the estimate of noise from the logarithm of the input envelope amplitude.

68. The audio output device of claim 66 wherein the electrical signals are attenuated and added to said outputs of the MAGC circuits.

69. The audio output device of claim 66, wherein the MAGC circuits have the ability to provide one gain function for noise and another gain function for desired signals.

70. The audio output device of claim 66, wherein the MAGC circuits may utilize a selected one of the gain functions of:

expansion, compression, and saturation.

71. The audio output device of claim 66, wherein the MAGC circuits may utilize selected ones of the gain functions of:

expansion, compression, and saturation.

72. The audio output device of claim 66, wherein the MAGC circuits provide a maximum limit to the gain.

74. The audio output device of claim 66, wherein the bandpass filter is implemented with bandpass filters having increasing bandwidth as the center frequency of the bandpass filter increases.

75. The audio output device of claim 66, wherein the bandpass filters are implemented so that all the bandpass filters have the same bandwidth.

77. The hearing aid device of claim 68, wherein:

said hearing compensation circuit comprises a high pass filter and a low pass filter;

an output of said low pass filter is coupled to an amplifier having an amplifier gain of K and having an amplifier output; and

said amplifier output and an output of said hearing compensation circuit are summed together.

76. A hearing aid device, comprising:

an input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to receive said electrical signals, each of said audio bandpass filters having an output;

a plurality of multiplicative automatic gain control (MAGC) circuits, each having at least one input and at least one output, an input of each of said MAGC circuits coupled to an output of one of said plurality of audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise suppression circuit; and

an output transducer responsive to said plurality of MAGC circuits.

wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise suppression circuit.

78. An hearing aid device comprising:

an input transducer for converting input acoustical energy into output electrical energy corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to the output of said input transducer;

a plurality of multiplicative automatic gain control (MAGC) circuits, each having at least one input and at least one output, an input of each of said MAGC circuits coupled to an output of one of said audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise estimation circuit; and

an output transducer responsive to said plurality of MAGC circuits,

wherein noise present in the acoustical energy is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

79. The hearing aid device of claim 78, wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

80. A hearing aid device, comprising:

an input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy;

a plurality of audio bandpass filters coupled to the output of said input transducer;

a plurality of multiplicative automatic gain control (MAGC) circuits, each having at least one input and at least one output, an input of each of said MAGC circuits coupled to an output of one of said audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise estimation circuit; and

an output transducer responsive to said plurality of multiplicative AGC circuits,

wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise estimation circuit.

81. The hearing aid device of claim 80, wherein the MAGC circuits include:

a first circuit to obtain an input envelope amplitude from the coupled acoustical bandpass filter output;

a second circuit responsive to the input envelope amplitude to provide the logarithm of the input envelope amplitude;

a hearing compensation circuit;

a noise estimation circuit for obtaining an estimate of noise; and

a subtraction circuit to subtract the estimate of noise from the logarithm of the input envelope amplitude.

82. The hearing aid device of claim 80 wherein the electrical signals are attenuated and added to said outputs of the MAGC circuits.

83. The hearing aid device of claim 80, wherein the MAGC circuits have the ability to provide one gain function for noise and another gain function for desired signals.

84. The hearing aid device of claim 80, wherein the MAGC circuits may utilize a selected one of the gain functions of:

expansion, compression, and saturation.

85. The hearing aid device of claim 80, wherein the MAGC circuits may utilize selected ones of the gain functions of:

expansion, compression, and saturation.

87. The hearing aid device of claim 80, wherein the bandpass filter is implemented with bandpass filters having increasing bandwidth as the center frequency of the bandpass filter increases.

88. The hearing aid device of claim 80, wherein the bandpass filters are implemented so that all the bandpass filters have the same bandwidth.