Patent US4622692A successfully refreshed from Google Patents.
US4622692A
Expired / Lapsed
US
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Noise reduction system
Assignee: LINEAR TECHNOLOGY Inc
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Filing: 1984-10-10
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Granted: 1986-11-11
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Expires: 2004-10-10
Abstract
Abstract Electronic circuitry as described which enhances the intelligibility of a speech signal corrupted by low-frequency noise while tending to retain frequency components of the signal characteristic of natural-sounding speech. The circuitry includes a broad band channel which passes the speech signal with little spectral distortion. A high-pass channel produces a high-pass signal corresponding to high-frequency components of the speech signal, components which in themselves provide the human ear with considerable information for discernment of different sounds. An operational amplifier in a summing configuration combines the broadband and high-pass signals to produce a processed speech signal with enhanced intelligibility. Gain control circuitry associated with the high-pass channel reduces gain in the high-pass channel with increasing intensity of high-frequency speech signal components thereby tending to enhance the speech signal to an increasing degree at low signal levels and to otherwise produce a processed speech signal suitable for reproduction of natural-sounding speech.
Inventors
- 👤 William A. Cole
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 23:11
CPC Classifications
H; H03; H03G; H03G9/00; H03G9/02; H03G9/025; H04; H04R; H04R25/00; H04R25/35; H04R25/356; H04R2225/00; H04R2225/43; H04R25/50; H04R25/502
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
328 words
Apparatus for enhancing the intelligibility of an audio-frequency electric speech signal corrupted by low frequency noise, comprising: (a) an input terminal for receiving said speech signal, (b) an output terminal, (c) summing means for adding together signals applied thereto to produce a sum signal, said summing means being connected to said output terminal, (d) a broadband channel connected between said input terminal and said summing means for producing from the speech signal a corresponding broadband signal and applying said broadband signal to said summing means, (e) a high-pass channel connected in parallel with said broadband channel between said input terminal and said summing means and comprising: (i) a high-pass filter connected to said input terminal for producing from said speech signal a high-pass signal which is substantially free of selected low-frequency components, (ii) an automatic gain control amplifier connected to said high-pass filter and having an output, for producing from said high-pass signal an amplified high-pass signal, (iii) said amplifier having a gain control terminal, and means responsive to the amplitude of a signal received at said gain control terminal for varying inversely therewith the gain of said amplifier, (iv) means connected to said output of said amplifier for rectifying said amplified high-pass signal and applying such rectified high-pass signal to said gain control terminal, for varying the gain of said amplifier inversely with the amplitude of said amplified high-pass signal, (v) the parameters of said amplifier being set such that said amplifier has substantially greater gain than that of said broadband channel when said high-pass signal is of low amplitude and such that the contribution of said amplified high-pass signal to said sum signal is small when said high-pass signal is of high amplitude, so that when said high-pass signal is of low amplitude, the contribution of said amplified high-pass signal enhances the intelligibility of said sum signal, and when said high-pass signal is of high amplitude, said sum signal will more faithfully represent natural sounding speech.
Claim 2
Dependent Claim
328 words
Apparatus for enhancing the intelligibility of an audio-frequency electric speech signal corrupted by low frequency noise, comprising: (a) an input terminal for receiving said speech signal, (b) an output terminal, (c) summing means for adding together signals applied thereto to produce a sum signal, said summing means being connected to said output terminal, (d) a broadband channel connected between said input terminal and said summing means for producing from the speech signal a corresponding broadband signal and applying said broadband signal to said summing means, (e) a high-pass channel connected in parallel with said broadband channel between said input terminal and said summing means and comprising: (i) a high-pass filter connected to said input terminal for producing from said speech signal a high-pass signal which is substantially free of selected low-frequency components, (ii) an automatic gain control amplifier connected to said high-pass filter and having an output, for producing from said high-pass signal an amplified high-pass signal, (iii) said amplifier having a gain control terminal, and means responsive to the amplitude of a signal received at said gain control terminal for varying inversely therewith the gain of said amplifier, (iv) means connected to said output of said amplifier for rectifying said amplified high-pass signal and applying such rectified high-pass signal to said gain control terminal, for varying the gain of said amplifier inversely with the amplitude of said amplified high-pass signal, (v) the parameters of said amplifier being set such that said amplifier has substantially greater gain than that of said broadband channel when said high-pass signal is of low amplitude and such that the contribution of said amplified high-pass signal to said sum signal is small when said high-pass signal is of high amplitude, so that when said high-pass signal is of low amplitude, the contribution of said amplified high-pass signal enhances the intelligibility of said sum signal, and when said high-pass signal is of high amplitude, said sum signal will more faithfully represent natural sounding speech.
Claim 3
Dependent Claim
24 words
Apparatus according to claim 1 wherein said means responsive to the amplitude signal received at said gain control terminal comprises a voltage controlled resistance.
References Cited (Backward Citations)
US3818149A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-11-10 | 1990-05-12 | 1990-11-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-11-10 | 1994-05-12 | 1994-11-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-11-10 | 1998-05-12 | 1998-11-11 | $7700.00 | Window Closed / Lapsed |