Patent US4815142A successfully refreshed from Google Patents.
US4815142A
Expired / Lapsed
US
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Noise reduction device in an electroacoustic system
Assignee: Dogself Sarl
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Filing: 1987-05-27
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Granted: 1989-03-21
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Expires: 2007-05-27
Abstract
Abstract The device comprises at least one correction circuit interposed in the electroacoustic system and comprising a band-pass filter receiving an input signal, a compressor limiter circuit connected to the output of the band-pass filter, a threshold detector circuit connected to the output of the compressor-limiter circuit and looped thereon in order to allow compression, by said compressor limiter circuit, of the signal issued from the band-pass filter, only if the input signal exceeds a predetermined threshold, and a summing-inverter circuit to which is applied, on the one hand, the signal issued from said compressor limiter circuit, and on the other hand, via an inverter circuit, the input signal applied to the input of the band-pass filter. According to the invention, a plurality of correction circuits can be cascade-mounted, said circuits comprising band-pass filters of which the pass-bands are different but do not necessarily overlap.
Inventors
- 👤 Miklos Imreh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 08:20
CPC Classifications
H; H03; H03G; H03G9/00; H03G9/02; H03G9/12; H03G9/18
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
224 words
A noise reduction device for an electroacoustic recording and reproducing system comprising at least one correction circuit interposed in the electroacoustic system, said correction circuit comprising, a band-pass filter having an input terminal for receiving an input signal and an output terminal, a compressor limiter circuit having first and second input terminals and an output terminal, a threshold detector circuit having an input terminal and an output terminal, a summing circuit having first and second inverting input terminals and an output terminal, and an inverter circuit having an input terminal for receiving the input signal and an output terminal, wherein the output terminal of the inverter circuit is connected to the first inverting input terminal of the summing circuit, the output terminal of the compressor limiter circuit is connected to the second inverting input of the summing circuit, the output terminal of the band-pass filter is connected to the first input terminal of the compressor limiter circuit, the output terminal of the threshold detector circuit is connected to the second input terminal of the compressor limiter circuit, and the output terminal of the compressor limiter circuit is connected to the input terminal of the threshold detector circuit, whereby the signal on the output terminal of the band-pass filter is compressed only if said signal exceeds a predetermined threshold detected by the threshold detector circuit.
Claim 2
Dependent Claim
224 words
A noise reduction device for an electroacoustic recording and reproducing system comprising at least one correction circuit interposed in the electroacoustic system, said correction circuit comprising, a band-pass filter having an input terminal for receiving an input signal and an output terminal, a compressor limiter circuit having first and second input terminals and an output terminal, a threshold detector circuit having an input terminal and an output terminal, a summing circuit having first and second inverting input terminals and an output terminal, and an inverter circuit having an input terminal for receiving the input signal and an output terminal, wherein the output terminal of the inverter circuit is connected to the first inverting input terminal of the summing circuit, the output terminal of the compressor limiter circuit is connected to the second inverting input of the summing circuit, the output terminal of the band-pass filter is connected to the first input terminal of the compressor limiter circuit, the output terminal of the threshold detector circuit is connected to the second input terminal of the compressor limiter circuit, and the output terminal of the compressor limiter circuit is connected to the input terminal of the threshold detector circuit, whereby the signal on the output terminal of the band-pass filter is compressed only if said signal exceeds a predetermined threshold detected by the threshold detector circuit.
Claim 3
Dependent Claim
43 words
A device as in claim 1, wherein a plurality of said correction circuits are cascade-mounted in the electroacoustic system and the pass-band for the band-pass filter in each of said correction circuits comprises a different range of frequencies which do not substantially overlap.
Claim 4
Dependent Claim
32 words
A device as in claim 1, wherein the threshold detector circuit comprises a variable gain linear amplifier connected to the output terminal of the compressor limiter circuit, and a voltage reference circuit.
Claim 5
Dependent Claim
35 words
A device as in claim 3, wherein the threshold detector circuit further comprises a delay circuit controlling the compressor limiter circuit with a predetermined time constant adapted to the pass-band frequencies of the band-pass filter.
Claim 6
Dependent Claim
39 words
A device as in claim 3, wherein the threshold detector circuit further comprises a voltage doubler circuit connected to the output terminal of the variable gain linear amplifier, and the voltage reference circuit comprises at least one Zener diode.
Claim 7
Dependent Claim
51 words
A device as in claim 1, wherein the compressor limiter circuit comprises an operational amplifier and a V-MOS field effect transistor controlled by the threshold detector circuit for selectively short-circuiting the input terminal to the operational amplifier when the threshold detector circuit detects that the predetermined voltage threshold has been exceeded.
Claim 8
Dependent Claim
26 words
A device as in claim 1, wherein the compressor limiter circuit comprises means for adjusting the voltage at the output terminal of the compresser limiter circuit.
Claim 9
Dependent Claim
23 words
A device as in claim 2, wherein the pass-band frequencies of the band-pass filters increase for each successive correction circuit mounted in cascade.
References Cited (Backward Citations)
US3757254A
Cited
US3784749A
Cited
US3930208A
Cited
US4035739A
Cited
US4071695A
Cited
US4218662A
Cited
FR2490856A1
Cited
US4550426A
Cited
GB2152785A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-03-20 | 1992-09-19 | 1993-03-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-03-20 | 1996-09-19 | 1997-03-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-03-20 | 2000-09-19 | 2001-03-21 | $7700.00 | Window Closed / Lapsed |