Digital signal processing hearing aid

• US 6,104,822 A
• Filed: 08/06/1997
• Issued: 08/15/2000
• Est. Priority Date: 10/10/1995
• Status: Expired due to Fees

• Current Assignee: GN Resound A/S (GN Store Nord A/S)
• Original Assignee: AudioLogic, Inc. (Cirrus Logic Incorporated)
• Inventors: Melanson, John L., Lindemann, Eric
• Primary Examiner(s): CHIN, VIVIAN C
• Application Number:
  US08/907,337
• Time in Patent Office: 1,105 Days
• Field of Search: 381/320, 381/321, 381/316, 381/317, 381/312, 381/314, 381/58, 381/98, 381/104, 381/106, 381/107, 381/109, 381/66
• US Class Current: 381/320
• CPC Class Codes: H04R 2225/41 Detection or adaptation of hearing aid parameters or programs to listening situation, e.g. pub, forest
• CPC Class Codes: H04R 2225/43 Signal processing in hearing aids to enhance the speech intelligibility
• CPC Class Codes: H04R 2430/03 Synergistic effects of band splitting and sub-band processing
• CPC Class Codes: H04R 25/453 electronically
• CPC Class Codes: H04R 25/505 using digital signal processing
• CPC Class Codes: H04R 25/70 Adaptation of deaf aid to hearing loss, e.g. initial electronic fitting

Abstract

A digital signal processing hearing aid is disclosed having a plurality of digital signal processing means for processing input digital signals, and a selector switch manipulable by a user for choosing which of the processing means to utilize. Each of the digital signal processing means is designed to provide optimal results in a particular listening environment. Since the user is allowed to choose which of the plurality of processing means to invoke, and since each processing means is specifically designed to operate in a particular listening environment, the hearing aid is capable of providing excellent results in a plurality of listening environments.

Claims

1. A hearing aid, comprising:

an input transducer for converting audio signals into analog electrical signals;

an analog-to-digital converter for converting said analog signals into digital signals;

a processor, capable of executing digital instructions;

a memory device for storing digital data, comprising a plurality of digital signal processing means, each capable of selectively receiving said input digital signals, and each capable of generating a set of output digital signals, each of said digital signal processing means capable of processing said input digital signals to implement a selected filtering strategy designed for a selected situation, each of said digital signal processing means comprising said digital instructions, said digital instructions completely implementing each of said filtering strategies when executed by said processor, at least one of said digital signal processing means comprising;

a filter bank analyzer for dividing said input digital signals into a plurality of individual frequency band signals;

a multi-band processor for processing said plurality of individual frequency band signals to derive a plurality of processed frequency band signals comprising;

means for generating a linear instantaneous power estimate for at least one of said individual frequency band signals to produce an instantaneous linear power estimate stream;

means for converting said instantaneous linear power estimate stream into an instantaneous logarithmic power estimate stream;

means for smoothing said instantaneous logarithmic power estimate stream to produce a smoothed logarithmic power estimate stream comprising;

means for processing said instantaneous logarithmic power estimate stream with a smoothing coefficient time constant to derive a processed power estimate stream;

means for storing a current smoothing filter state;

means for processing said current smoothing filter state with said processed power estimate stream to derive a new smoothing filter state, said new smoothing filter state being stored in said storing means, and representing said smoothed logarithmic power estimate stream; and

means for adaptively generating a new smoothing coefficient time constant based on a comparison of said current smoothing filter state with said instantaneous power estimate stream;

means for calculating a gain coefficient based on said smoothed logarithmic power estimate stream; and

means for processing said one of said individual frequency band signals and said gain coefficient to generate one of said plurality of processed frequency band signals; and

a filter bank combiner for combining said plurality of processed frequency band signals to derive said output digital signals;

wherein said filter-bank analyzer, said multi-band processor, and said filter bank combiner are digital instructions stored in said memory device and capable of being executed by said processor;

a selector manipulatable by a user for selecting one of said digital signal processing means to use in processing said input digital signals, said selector enabling the user to dynamically select which of said filtering strategies to implement in any particular situation, each of said filtering strategies optimized for a particular listening environment;

a digital-to-analog converter for converting said output digital signals into a set of output analog electrical signals; and

an output transducer for converting said output analog electrical signals into a set of output audio signals.

2. A hearing aid, comprising:

an input transducer for converting audio signals into analog electrical signals;

an analog-to-digital converter for converting said analog signals into input digital signals;

a storage for storing a plurality of instruction sequences, each instruction sequence, when executed, implementing a selected digital signal processing strategy, each of said digital processing strategies being optimized for a particular listening environment, at least one of said instruction sequences comprising;

a filter bank analyzer portion for dividing said input digital signals into a plurality of individual frequency band signals;

a multi-band processor portion for processing said plurality of individual frequency band signals to derive a plurality of processed frequency band signals comprising;

means for generating a linear instantaneous power estimate for at least one of said individual frequency band signals to produce an instantaneous linear power estimate stream;

means for converting said instantaneous linear power estimate stream into an instantaneous logarithmic power estimate stream;

means for smoothing said instantaneous logarithmic power estimate stream to produce a smoothed logarithmic power estimate stream comprising;

means for processing said instantaneous logarithmic power estimate stream with a smoothing coefficient time constant to derive a processed power estimate stream;

means for storing a current smoothing filter state;

means for processing said current smoothing filter state with said processed power estimate stream to derive a new smoothing filter state, said new smoothing filter state being stored in said storing means, and representing said smoothed logarithmic power estimate stream; and

means for adaptively generating a new smoothing coefficient time constant based on a comparison of said current smoothing filter state with said instantaneous power estimate stream;

means for calculating a gain coefficient based on said smoothed logarithmic power estimate stream; and

means for processing said one of said individual frequency band signals and said gain coefficient to generate one of said plurality of processed frequency band signals; and

a filter bank combiner portion for combining said plurality of processed frequency band signals to derive said output digital signals;

a logic unit, coupled to said digital-to-analog converter, for executing one of said instruction sequences to process said input digital signals in accordance with one of the selected digital signal processing strategies, said logic unit providing a set of output digital signals;

a program sequencer coupled to said logic unit and said storage for selectively sending one of said instruction sequences to said logic unit for execution thereby;

an instruction sequence selector, coupled to said program sequencer, manipulatable by a user for controlling said program sequencer to select one of said program sequences to send from said storage to said logic unit, said selector enabling the user to dynamically select which of said digital signal processing strategies to implement for a particular listening environment;

a digital-to-analog converter for converting said output digital signals into a set of output analog electrical signals; and

an output transducer for converting said output analog electrical signals into a set of output audio signals.

3. A hearing aid, comprising:

an input transducer for converting audio signals into analog electrical signals;

an analog-to-digital converter for converting said analog signals into input digital signals;

a memory device for storing digital instructions representing a plurality of filtering strategies, including;

a filter bank analyzer for dividing said input digital signals into a plurality of individual frequency band signals, said analyzer comprising;

a first section of complementary comb filters for processing said input digital signals to provide a plurality of intermediate frequency band signals; and

a final section of complementary comb filters for processing said intermediate frequency band signals to provide said plurality of individual frequency band signals;

a multi-band processor for processing said plurality of individual frequency band signals to derive a plurality of processed frequency band signals comprising;

means for generating a linear instantaneous power estimate for at least one of said individual frequency band signals to produce an instantaneous linear power estimate stream;

means for converting said instantaneous linear power estimate stream into an instantaneous logarithmic power estimate stream;

means for smoothing said instantaneous logarithmic power estimate stream to produce a smoothed logarithmic power estimate stream comprising;

means for processing said instantaneous logarithmic power estimate stream with a smoothing coefficient time constant to derive a processed power estimate stream;

means for storing a current smoothing filter state;

means for processing said current smoothing filter state with said processed power estimate stream to derive a new smoothing filter state, said new smoothing filter state being stored in said storing means, and representing said smoothed logarithmic power estimate stream; and

means for adaptively generating a new smoothing coefficient time constant based on a comparison of said current smoothing filter state with said instantaneous power estimate stream;

means for calculating a gain coefficient based on said smoothed logarithmic power estimate stream; and

means for processing said one of said individual frequency band signals and said gain coefficient to generate one of said plurality of processed frequency band signals; and

a filter bank combiner for combining said plurality of processed frequency band signals to derive said output digital signals;

wherein said filter bank analyzer includes said digital instructions, said digital instructions completely implementing each of said filtering strategies when executed by said processor;

a selector, coupled to said memory device and capable of being manipulated by a user for dynamically selecting one of said filtering strategies;

a digital-to-analog converter for converting said output digital signals into a set of output analog electrical signals; and

an output transducer for converting said output analog electrical signals into a set of output audio signals.

4. A hearing aid, comprising:

an input transducer for converting audio signals into analog electrical signals;

an analog-to-digital converter for converting said analog signals into input digital signals;

a memory device for storing digital instructions representing a plurality of filtering strategies, including;

a filter bank analyzer for dividing said input digital signals into a plurality of individual frequency band signals, said analyzer comprising;

a section of complementary comb filters for processing said input digital signals to provide a plurality of intermediate frequency band signals; and

a section of recursive filter resonators for processing said intermediate frequency band signals to provide said plurality of individual frequency band signals;

a multi-band processor for processing said plurality of individual frequency band signals to derive a plurality of processed frequency band signals comprising;

means for generating a linear instantaneous power estimate for at least one of said individual frequency band signals to produce an instantaneous linear power estimate stream;

means for converting said instantaneous linear power estimate stream into an instantaneous logarithmic power estimate stream;

means for smoothing said instantaneous logarithmic power estimate stream to produce a smoothed logarithmic power estimate stream;

means for calculating a gain coefficient based on said smoothed logarithmic power estimate stream; and

means for processing said one of said individual frequency band signals and said gain coefficient to generate one of said plurality of processed frequency band signals; and

a filter bank combiner for combining said plurality of processed frequency band signals to derive a set of output digital signals;

wherein said filter bank analyzer, said multi-band processor, and said filter bank combiner each include said digital instructions, said digital instructions completely implementing each of said filtering strategies when executed by said processor;

selecting means, coupled to said memory device and capable of being manipulated by a user for dynamically selecting one of said filtering strategies;

a digital-to-analog converter for converting said output digital signals into a set of output analog electrical signals; and

an output transducer for converting said output analog electrical signals into a set of output audio signals.

5. A hearing aid, comprising:

an input transducer for converting audio signals into analog electrical signals;

an analog-to-digital converter for converting said analog signals into input digital signals;

means for generating a linear instantaneous power estimate for at least a portion of said input digital signals to produce an instantaneous linear power estimate stream;

a memory device for storing digital instructions representing a plurality of filtering strategies, including;

means for converting said instantaneous linear power estimate stream into an instantaneous logarithmic power estimate stream;

means for smoothing said instantaneous logarithmic power estimate stream to produce a smoothed logarithmic power estimate stream comprising;

means for processing said instantaneous logarithmic power estimate stream with at smoothing coefficient time constant to derive a processed power estimate stream;

means for storing a current smoothing filter state;

means for processing said current smoothing filter state with said processed power estimate stream to derive a new smoothing filter state, said new smoothing filter state being stored in said storing means, and representing said smoothed logarithmic power estimate stream; and

means for adaptively generating a new smoothing coefficient time constant based on a comparison of said current smoothing filter state with said instantaneous power estimate stream; and

means for receiving and processing said smoothed logarithmic power estimate stream and said input digital signals to derive a set of output digital signals;

wherein said means for converting, said means for smoothing, and said means for receiving each include said digital instructions, said digital instructions completely implementing each of said filtering strategies when executed by said processor;

selecting means, coupled to said memory device and capable of being manipulated by a user for dynamically selecting one of said filtering strategies;

a digital-to-analog converter for converting said output digital signals into a set of output analog electrical signals; and

an output transducer for converting said output analog electrical signals into a set of output audio signals.