Electronic filters, signal conversion apparatus, hearing aids and methods

An electronic filter for filtering an electrical signal, comprising:

• a filter having an input for receiving a signal to be filtered, having an output producing a filtered signal and having signal processing means including logarithmic filter means producing an intermediate output signal;
• said filter having a series of filter stage means having inputs and outputs coupled in cascade, each said filter stage means filtering signals at its input according to electrical representations of filter parameters;
• electronic control means coupled to said filter for altering the electrical representations to vary a value of each of said filter parameters in substantially constant percentage amounts of the value of that one of said filter parameters;
• and
• said series of filter stage means including means for filtering signals through the series of filter stage means from a first to a last of said filter stage means and then filtering signals back through said series of filter stage means from the last to the first of said filter stage means to produce the filtered signal.

An electronic filter for filtering an electrical signal having a polarity, comprising:

• a filter having an input for receiving a signal to be filtered, having an output producing a filtered signal and having signal processing means including logarithmic filter means producing an intermediate output signal;
• said filter having a plurality of filter stages having inputs and outputs coupled in cascade, each said filter stage respectively filtering signals at its input according to electrical representations of filter parameters;
• said filter including means for filtering signals through the series of filter stages from a first to a last of said filter stages and then filtering signals back through said series of filter stages form the last to the first of said filter stages;
• and
• electronic control means coupled to said filter for altering the electrical representations to vary a value of each of said filter parameters in substantially constant percentage amounts of the value of that one of said filter parameters.

An electronic filter for an electroacoustic system having microphone means for generating an electrical output from external sounds and electrically driven transducer means for emitting sound, some of the sound emitted by the transducer means returning to the microphone means to add a feedback contribution to its electrical output, the electronic filter comprising:

• means for converting the electrical output of the microphone means to a logarithmic electrical representation;
• first means for combining the microphone output so converted with an adaptive output in logarithmic electrical form to produce a combined signal input in logarithmic electrical form;
• means for electronically filtering the combined signal input in logarithmic form to produce a filtered signal in logarithmic form;
• means for generating a distinct signal;
• second means for combining the filtered signal with the distinct signal for the transducer means;
• and
• said means for electronically filtering also including logarithmic adaptive filter means having electrically stored parameters representing coefficients in logarithmic form, said means for electronically filtering further including linear control means for continually altering the coefficients to vary them in magnitude in substantially constant percentage amounts, said logarithmic adaptive filter means further including means for electronic processing of the filtered signal and the distinct signal relative to the electrically stored parameters to produce an adaptive output in logarithmic form to said first means for combining to substantially offset the feedback contribution in the electrical output of the microphone means in the electroacoustic system.

An electronic filter for an electroacoustic system having microphone means for generating an electrical output from external sounds and electrically driven transducer means for emitting sound corresponding to the external sound, some of the sound emitted by the transducer means returning to the microphone means to add a feedback contribution to its electrical output, the electronic filter comprising:

• means for converting the electrical output of the microphone means to an electrical representation;
• first means for combining the microphone output so converted with an adaptive output to produce a combined signal input;
• electronic filter means for electronically filtering the combined signal input to produce a filtered signal;
• adaptive filter means having electrically stored parameters representing coefficients, said adaptive filter means including linear control means for altering the coefficients in substantially constant percentage amounts, said linear control means interconnected with said electronically filtering means, said adaptive filter means further including means for electronic processing of the filtered signal relative to the electrically stored coefficients to produce said adaptive output to said first means for combining to substantially offset the feedback contribution in the electrical output of the microphone means in the electroacoustic system;
• means for generating a distinct signal;
• and
• second means for combining the filtered signal with the distinct signal for the transducer means.