Electronic hearing aid with gain control means for eliminating low frequency noise
First Claim
1. A hearing aid device for the compensation of hearing deficiencies and for enhancing the intelligibility of audio-frequency speech signals corrupted by low frequency noise, said device comprising:
- a signal input transducer for converting input audio speech signals to electric speech signals,an output terminal adapted for connection to an output transducer for supplying acoustic output signals compensated for a hearing deficiency of a hearing-impaired person, anda control circuit having an input terminal connected between the output side of said input transducer and said output terminal, said control circuit comprising;
summing means for summing signals applied thereto and producing a sum signal;
a low-frequency channel, including a first band-pass filter, connected between said input terminal and said summing means for coupling to said summing means a low-frequency signal which is substantially free of frequency components above a selected frequency;
a high-frequency channel connected in parallel with said low-frequency channel between said input terminal and said summing means and comprising;
a second band-pass filter connected to said input terminal for producing from said electric speech signal a high-frequency signal which is substantially free of frequency components below said selected frequency,a variable gain amplifier connected to the output of said high-pass filter and having a gain control terminal and an output terminal, for compressing said high-frequency signal and producing a compressed high-frequency signal at its output terminal,means for generating a control signal for controlling the gain of said amplifier including means connected to the output of said high-frequency filter for controllably amplifying said high-frequency signal, means for rectifying said amplified high-frequency signal, and means for comparing the level of such rectified high-pass signal against a reference level and applying to said gain control terminal a signal proportional to the difference, for varying the gain of said amplifier inversely with the amplitude of said rectified high-frequency signal, anda potentiometer connected between the output terminal of said amplifier and said summing means for coupling a controllable portion of said compressed high-frequency signal to said summing means;
a power amplifier having an input terminal and an output terminal connected to said device output terminal; and
a potentiometer connected between the output of said summing means and the input terminal of said power amplifier for coupling a controllable portion of said sum signal to said power amplifier.
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Abstract
Electronic circuitry is described which enhances the intelligibility of a speech signal corrupted by low-frequency noise and certain flaws of miniaturized hearing aids are overcome by packaging the circuitry in a housing to be worn on the body of the hearing-impaired person and electrically coupling the output of the circuit to a high quality of a type to be worn in the ear speaker. The circuitry includes a low-frequency channel which passes components of the speech signal between about 600 Hz and about 1.2 KHz, and a parallel high-frequency channel which passes speech signal components between about 1.7 KHz and 4.6 KHz. The high-frequency channel includes a gain control amplifier for compressing the dynamic range of high-frequency components and means for adjusting the level of the compressed high-frequency signal relative to the level of signals passed by the low-frequency channel. The low-frequency and high-frequency signals are combined in a summing amplifier, the output level of which is controlled by a volume control and then amplified in power sufficiently to drive a wide dynamic range external speaker.
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Citations
7 Claims
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1. A hearing aid device for the compensation of hearing deficiencies and for enhancing the intelligibility of audio-frequency speech signals corrupted by low frequency noise, said device comprising:
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a signal input transducer for converting input audio speech signals to electric speech signals, an output terminal adapted for connection to an output transducer for supplying acoustic output signals compensated for a hearing deficiency of a hearing-impaired person, and a control circuit having an input terminal connected between the output side of said input transducer and said output terminal, said control circuit comprising; summing means for summing signals applied thereto and producing a sum signal; a low-frequency channel, including a first band-pass filter, connected between said input terminal and said summing means for coupling to said summing means a low-frequency signal which is substantially free of frequency components above a selected frequency; a high-frequency channel connected in parallel with said low-frequency channel between said input terminal and said summing means and comprising; a second band-pass filter connected to said input terminal for producing from said electric speech signal a high-frequency signal which is substantially free of frequency components below said selected frequency, a variable gain amplifier connected to the output of said high-pass filter and having a gain control terminal and an output terminal, for compressing said high-frequency signal and producing a compressed high-frequency signal at its output terminal, means for generating a control signal for controlling the gain of said amplifier including means connected to the output of said high-frequency filter for controllably amplifying said high-frequency signal, means for rectifying said amplified high-frequency signal, and means for comparing the level of such rectified high-pass signal against a reference level and applying to said gain control terminal a signal proportional to the difference, for varying the gain of said amplifier inversely with the amplitude of said rectified high-frequency signal, and a potentiometer connected between the output terminal of said amplifier and said summing means for coupling a controllable portion of said compressed high-frequency signal to said summing means; a power amplifier having an input terminal and an output terminal connected to said device output terminal; and a potentiometer connected between the output of said summing means and the input terminal of said power amplifier for coupling a controllable portion of said sum signal to said power amplifier. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification