US 5,706,352 A · Adaptive gain and filtering circuit for a sound reproduction system

Abstract

Adaptive compressive gain and level dependent spectral shaping circuitry for a hearing aid include a microphone to produce an input signal and a plurality of channels connected to a common circuit output. Each channel has a preset frequency response. Each channel includes a filter with a preset frequency response to receive the input signal and to produce a filtered signal, a channel amplifier to amplify the filtered signal to produce a channel output signal, a threshold register to establish a channel threshold level, and a gain circuit. The gain circuit increases the gain of the channel amplifier when the channel output signal falls below the channel threshold level and decreases the gain of the channel amplifier when the channel output signal rises above the channel threshold level. A transducer produces sound in response to the signal passed by the common circuit output.

Claims50

Dependent claims

A hearing aid comprising:

a microphone for producing an input signal in response to sound;
a plurality of channels connected to a common output, each channel comprising:
a filter with preset parameters for receiving the input signal and for producing a filtered signal;
a channel amplifier responsive to the filtered signal for producing a channel output signal;
a channel gain register for storing a gain value;
a channel preamplifier having a preset gain for amplifying the gain value to produce a gain signal;
wherein the channel amplifier is responsive to the channel preamplifier for varying the gain of the channel amplifier as a function of the gain signal;
means for establishing a channel threshold level for the channel output signal;
and
means, responsive to the channel output signal and the channel threshold level, for increasing the gain value when the channel output signal falls below the channel threshold level and for decreasing the gain value when the channel output signal rises above the channel threshold level;
wherein the channel output signals are combined to produce an adaptively compressed and filtered output signal;
and
a transducer for producing sound as a function of the adaptively compressed and filtered output signal.

10 more elements

A hearing aid comprising:

a microphone for producing an input signal in response to sound;
a plurality of channels connected to a common output, each channel comprising:
a filter with preset parameters for receiving the input signal and for producing a filtered signal;
a channel amplifier responsive to the filtered signal for producing a channel output signal;
a channel gain register for storing a gain value;
a channel preamplifier having a preset gain for amplifying the gain value to produce a gain signal;
wherein the channel amplifier is responsive to the channel preamplifier for varying the gain of the channel amplifier as a function of the gain signal;
means for establishing a channel threshold level for the channel output signal;
and
means, responsive to the channel output signal and the channel threshold level, for increasing the gain value when the channel output signal falls below the channel threshold level and for decreasing the gain value when the channel output signal rises above the channel threshold level;
a second channel amplifier responsive to the filtered signal for producing a second channel output signal;
and
means for programming the gain of the second channel amplifier as a function of the gain value for the respective channel;
wherein the second channel output signal is combined with the second channel output signals of the other channels for producing a programmably compressed and filtered output signal;
and
a transducer for producing sound as a function of the programmably compressed and filtered output signal.

13 more elements

A hearing aid comprising:

a microphone for producing an input signal in response to sound;
an amplifier for receiving the input signal and for producing an output signal;
means for establishing a threshold level for the output signal;
a comparator for producing a control signal as a function of the level of the output signal being greater or less than the threshold level;
a gain register for storing a gain setting;
an adder responsive to the control signal for increasing the gain setting by a first preset magnitude when the output signal falls below the threshold level and for decreasing the gain setting by a second preset magnitude when the output signal rises above the threshold level;
wherein the gain register stores the gain setting as a first plurality of least significant bits and as a second plurality of most significant bits;
wherein the first preset magnitude comprises a number of bits less than or equal to a total number of bits comprising the least significant bits;
wherein the amplifier is responsive to the most significant bits stored in the gain register for varying the gain of the amplifier as a function of the gain setting;
and
a transducer for producing sound as a function of the output signal.

8 more elements

A hearing aid comprising a plurality of channels connected to a common output, each channel comprising:

a filter with preset parameters for receiving an input signal in the audible frequency range for producing a filtered signal;
a channel amplifier responsive to the filtered signal for producing a channel output signal;
a channel gain register for storing a gain value;
a channel preamplifier having a preset gain for amplifying the gain value to produce a gain signal;
wherein the channel amplifier is responsive to the channel preamplifier for varying the gain of the channel amplifier as a function of the gain signal;
means for establishing a channel threshold level for the channel output signal;
and
means, responsive to the channel output signal and the channel threshold level, for increasing the gain value up to a predetermined limit when the channel output signal falls below the channel threshold level and for decreasing the gain value when the channel output signal rises above the channel threshold level;
wherein the channel output signals are combined to produce an adaptively compressed and filtered output signal.

6 more elements

A hearing aid for use by a person having a hearing impairment spanning a predetermined frequency range, the hearing aid comprising:

a microphone for producing an input signal in response to sound;
only one broadband filtering channel spanning the predetermined frequency range of the hearing impairment, said channel comprising:
a variable filter with separately variable filter parameters for receiving the input signal and for producing an adaptively filtered signal;
and an amplifier for receiving the adaptively filtered signal and for producing an amplified adaptively filtered output signal;
wherein said broadband filtering channel has a bandwidth corresponding to the predetermined frequency range of the hearing impairment;
a preset filter with preset parameters responsive to the input signal for producing a characteristic signal;
a detector responsive to the characteristic signal for producing a control signal, the detector including means for programming the time constant of the detector;
means responsive to the detector for producing a log value representative of the control signal;
a memory for storing a preselected table of log values, filter parameters and gain values;
wherein the memory is responsive to the log value producing means for selecting a filter parameter and a gain value from the preselected table for the variable filter and the amplifier, respectively, as a function of the produced log value;
wherein the variable filter and the amplifier are responsive to the memory for varying the parameters of the variable filter and varying the gain of the amplifier as a function of the selected filter parameter and gain value, respectively;
and wherein said hearing aid does not include the use of a microprocessor;
and
a transducer for producing sound as a function of the amplified adaptively filtered output signal.

11 more elements

A hearing aid comprising:

a microphone for producing an input signal in response to sound;
a plurality of channels connected to a common output, each channel comprising a filter with preset parameters for receiving the input signal and for producing a filtered signal and an amplifier responsive to the filtered signal for producing a channel output signal;
a second filter with preset parameters responsive to the input signal for producing a characteristic signal;
a detector responsive to the characteristic signal for producing a control signal, the detector including means for programming the time constant of the detector;
means responsive to the detector for producing a log value representative of the control signal;
and
a memory for storing a preselected table of log values and gain values;
wherein the memory is responsive to the log value producing means for selecting a gain value from the preselected table for each of the amplifiers in the channels as a function of the produced log value, and wherein each of the amplifiers in the channels is responsive to the memory for separately varying the gain of the respective amplifier as a function of the respective selected gain value;
and
a transducer for producing sound as a function of the combined channel output signals;
wherein said hearing aid does not include the use of a microprocessor.

8 more elements

A hearing aid comprising:

a plurality of channels connected to a common output, each channel comprising:
a filter with preset parameters for receiving an input signal in the audible frequency range and for producing a filtered signal;
a channel amplifier responsive to the filtered signal for producing a channel output signal;
means for establishing a channel threshold level for the channel output signal;
a comparator for producing a control signal as a function of the level of the channel output signal being greater or less than the channel threshold level;
a channel gain register for storing a gain setting;
an adder responsive to the control signal for increasing the gain setting by a first preset magnitude when the channel output signal falls below the channel threshold level and for decreasing the gain setting by a second preset magnitude when the channel output signal rises above the channel threshold level;
and
a second channel gain register for storing a predetermined channel gain value to define an operating range for the channel as a function of a signal level of the input signal;
wherein the channel amplifier is responsive to the gain register and to the second channel gain register for varying the gain of the channel amplifier as a function of the gain setting and the predetermined channel gain value;
and
wherein the channel output signals are combined to produce an adaptively compressed and filtered output signal.

9 more elements

Dependencies are inferred from the claim text.

Adaptive gain and filtering circuit for a sound reproduction system

Life of this patent

Adaptive gain and filtering circuit for a sound reproduction system

Life of this patent

Abstract

Claims50