US3757254A
Expired / Lapsed
US
⏱️ 0.0 years remaining
N system noise reduction system and apparatus using a compression and expansio
Assignee: Victor Company of Japan Ltd
•
Filing: 1971-06-03
•
Granted: 1973-09-04
•
Expires: 1991-06-03
Abstract
Abstract A noise reduction system employs a compression and expansion system using a compressor and an expandor to reduce noise in a signal transmitted through a transmission system. The compressor side of the system comprises a compression circuit means provided in an open loop, through which the signal passes. A control circuit means generates a control voltage in accordance with the level of the output signal from the compression circuit means. This control voltage is applied to the compression circuit means, thereby to control compression ratio. The expandor side comprises an expansion circuit means which is provided in a negative feedback loop of a negative feedback amplifier. A control circuit means generates a control voltage in accordance with the level of the input signal to the negative feedback amplifier. This control voltage is applied to the expansion circuit means, thereby to control expansion ratio. The compressor and the expandor are so constructed that a coefficient k of amplitude control characteristic of the compressor, and a feedback ratio Beta of the expandor become equal to each other. The expansion apparatus can be constructed independently and used in the aforementioned system.
Inventors
- 👤 N Takahashi
- 👤 Y Ishigaki
- 👤 Y Itoh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 21:15
CPC Classifications
H; H03; H03G; H03G9/00; H03G9/02; H03G9/12; H03G9/18
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
418 words
cA noise reduction system employing a compression and expansion system comprising: compressor means including compression circuit means which compresses the amplitude of an input signal with a compression ratio which is variable in accordance with a control voltage applied thereto, said compression circuit means having two control element circuits including control elements with resistance values which vary in accordance with said control voltage, first control circuit means which generates a control voltage in accordance with the level of the output signal of said compression circuit means and applies said control voltage to said compression circuit means, a first signal splitting circuit means for splitting its input signal into two signals having mutually opposing phases and for supplying said two signals respectively to said two control element circuits, first phase inverting circuit means for inverting the phase of the output from one of said two control element circuits of said compression circuit means to mix said inverted output with the output from the other control element circuit; system means for transmitting said output signal of said compressor means; expandor means including negative feedback amplifier circuit means to which the output signal from said compressor is supplied after having been transmitted through said system means, said negative feedback amplifier circuit means having negative feedback circuit means for feeding back the output signal from said negative feedback amplifier circuit means to the input side thereof, said negative feedback circuit means having a feedback ratio which is variable in accordance with a control voltage applied thereto, second control circuit means to which the output signal from said compressor is supplied after having been transmitted through said system means, said second control circuit generating a control voltage in accordance with the level of the signal supplied thereto and applying it to said negative feedback circuit, two control element circuits having control elements with resistance values which vary in accordance with said control voltage, a second signal splitting circuit means for splitting its input signal into two signals having mutually opposing phases and supplying them respectively to said two control element circuits of said negative feedback circuit, and a second phase inverting circuit for inverting the phase of the output from one of said two control element circuit means to mix said output with the output from the other control element circuit, wherein a coefficient k of a total amplitude control characteristic of said compressor and a feedback ratio Beta of said negative feedback circuit are selected to be substantially equal to each other.
Claim 2
Dependent Claim
418 words
cA noise reduction system employing a compression and expansion system comprising: compressor means including compression circuit means which compresses the amplitude of an input signal with a compression ratio which is variable in accordance with a control voltage applied thereto, said compression circuit means having two control element circuits including control elements with resistance values which vary in accordance with said control voltage, first control circuit means which generates a control voltage in accordance with the level of the output signal of said compression circuit means and applies said control voltage to said compression circuit means, a first signal splitting circuit means for splitting its input signal into two signals having mutually opposing phases and for supplying said two signals respectively to said two control element circuits, first phase inverting circuit means for inverting the phase of the output from one of said two control element circuits of said compression circuit means to mix said inverted output with the output from the other control element circuit; system means for transmitting said output signal of said compressor means; expandor means including negative feedback amplifier circuit means to which the output signal from said compressor is supplied after having been transmitted through said system means, said negative feedback amplifier circuit means having negative feedback circuit means for feeding back the output signal from said negative feedback amplifier circuit means to the input side thereof, said negative feedback circuit means having a feedback ratio which is variable in accordance with a control voltage applied thereto, second control circuit means to which the output signal from said compressor is supplied after having been transmitted through said system means, said second control circuit generating a control voltage in accordance with the level of the signal supplied thereto and applying it to said negative feedback circuit, two control element circuits having control elements with resistance values which vary in accordance with said control voltage, a second signal splitting circuit means for splitting its input signal into two signals having mutually opposing phases and supplying them respectively to said two control element circuits of said negative feedback circuit, and a second phase inverting circuit for inverting the phase of the output from one of said two control element circuit means to mix said output with the output from the other control element circuit, wherein a coefficient k of a total amplitude control characteristic of said compressor and a feedback ratio Beta of said negative feedback circuit are selected to be substantially equal to each other.
Claim 3
Dependent Claim
42 words
The system as defined in claim 1 wherein said signal transmission system means comprises a recording medium and means for recording the output signal from said compressor on said recording medium, and means for reproducing the recorded signal from said recording medium.
Claim 4
Dependent Claim
26 words
In the system as defined in claim 1, wherein said transmission system comprises a recording medium on which the output signal from said compressor is recorded.
Claim 5
Dependent Claim
41 words
The system as defined in claim 1 wherein said compression circuit and said negative feedback circuit means have substantially the same circuit construction, and said first control circuit means and said second control circuit means have substantially the same circuit construction.
Claim 6
Dependent Claim
63 words
The system as defined in claim 1 wherein each of said compression circuit means and said negative feedback circuit means respectively comprise a bridge circuit having in one branch a control element with a resistance value which varies in accordance with said control voltage and having an element connected in said bridge connection, the impedance of said last named element varying with frequency.
Claim 7
Dependent Claim
39 words
The system as defined in claim 5 wherein said control element which has a resistance value which varies in accordance with said control voltage comprises NPN type and PNP type transistors which are connected in parallel with each other.
Claim 8
Dependent Claim
143 words
An expansion apparatus for use in the system as defined in claim 1, said expansion apparatus comprising a second negative feedback amplifier circuit, means for supplying the output signal from said compressor means as an input signal to said second negative feedback amplifier after said signal has been transmitted through the signal transmission system, the negative feedback amplifier circuit means further including a negative feedback circuit for feeding back the output signal from said negative feedback amplifier circuit to the input side thereof, the feedback ratio being variable in accordance with a control voltage applied thereto, control circuit means to which the output signal from said compressor is supplied after being transmitted through said signal transmission system means for generating a control voltage in accordance with the level of the supplied output signal and for applying said control voltage to said expansion circuit.
Claim 9
Dependent Claim
92 words
The apparatus as defined in claim 7 wherein said expansion circuit means comprises two control element circuits comprising control elements with resistance values which are variable in accordance with said control voltage, said apparatus further comprising a signal splitting circuit for splitting its input signal into two signals having mutually opposite phases and suppying them respectively to said two control element circuits, and phase inverting circuit means for inverting the phases of the output of one of said two control element circuits to mix said output with the other control element circuit.
Claim 10
Dependent Claim
127 words
The apparatus as defined in claim 7 wherein said expansion circuit comprises an active element with a variable amplification degree for providing a resistance value which is variable in accordance with said control voltage and which is biased by said control voltage, said expansion apparatus further comprising a bias stabilizing circuit comprising an amplifier which drives said active element having said variable amplification degree responsive to an output of said amplifier, and circuit means comprising a diode which detects a very small variation of a power source voltage for supplying a bias to said active element with a variable amplification degree to simultaneously vary the bias of said amplifier, wherein a voltage between a gate and the degree active element are equivalently maintained at a constant value.
Claim 11
Dependent Claim
52 words
The apparatus as defined in claim 7 wherein said expansion circuit means comprises a bridge circuit having in one branch a control element with a resistance value which is variable in accordance with said control voltage and having an element with an impedance which varies with a frequency connected in bridge connection.
Claim 12
Dependent Claim
35 words
The apparatus as defined in claim 10 wherein said control element resistance which varies in accordance with said control voltage comprises NPN type and PNP type transistors which are connected in parallel with each other.
Claim 13
Dependent Claim
265 words
A noise reduction system employing a compression and expansion system comprising: compressor means including compression circuit means which compresses the amplitude of an input signal having a predetermined band width, said compressor acting on a narrow frequency band having less than said predetermined width with a compression ratio which is variable in accordance with control voltage applied thereto, first control circuit means which generates a control voltage in accordance with the level of the output signal of said compression circuit means and applies said control voltage to said compression circuit means; system means for transmitting said compression circuit output signal; expandor means including a negative feedback amplifier circuit means to which the output signal from said compressor is supplied after having been transmitted through said transmitting system means, said negative feedback amplifier circuit means having a negative feedBack circuit means for feeding back the output signal from said negative feedback amplifier means to the input side thereof, said negative feedback circuit means having a feedback ratio which is variable in said narrow frequency band in accordance with a control voltage applied thereto, and second control circuit means to which the output signal from said compressor means is supplied after having been transmitted through said transmitting system means, said second control circuit generating a control voltage in accordance with the level of the signal supplied thereto and applying control voltage to said negative feedback circuit, wherein a coefficient k of a total amplitude control characteristic of said compressor means and feedback ratio Beta of said negative feedback are selected to be substantially equal to each other.
Claim 14
Dependent Claim
265 words
A noise reduction system employing a compression and expansion system comprising: compressor means including compression circuit means which compresses the amplitude of an input signal having a predetermined band width, said compressor acting on a narrow frequency band having less than said predetermined width with a compression ratio which is variable in accordance with control voltage applied thereto, first control circuit means which generates a control voltage in accordance with the level of the output signal of said compression circuit means and applies said control voltage to said compression circuit means; system means for transmitting said compression circuit output signal; expandor means including a negative feedback amplifier circuit means to which the output signal from said compressor is supplied after having been transmitted through said transmitting system means, said negative feedback amplifier circuit means having a negative feedBack circuit means for feeding back the output signal from said negative feedback amplifier means to the input side thereof, said negative feedback circuit means having a feedback ratio which is variable in said narrow frequency band in accordance with a control voltage applied thereto, and second control circuit means to which the output signal from said compressor means is supplied after having been transmitted through said transmitting system means, said second control circuit generating a control voltage in accordance with the level of the signal supplied thereto and applying control voltage to said negative feedback circuit, wherein a coefficient k of a total amplitude control characteristic of said compressor means and feedback ratio Beta of said negative feedback are selected to be substantially equal to each other.
Claim 15
Dependent Claim
23 words
The system as defined in claim 12 wherein said narrow frequency band is the frequency band in which the noise distribution is greater.
Claim 16
Dependent Claim
24 words
The system as defined in claim 12 wherein said narrow frequency band is the high and middle frequency bands of an audio frequency range.
Claim 17
Dependent Claim
111 words
The system as defined in claim 12 wherein said compressor means further includes a first filter circuit to which is applied the output signal of said compression circuit means, said first filter passing the signal only in said narrow frequency band, and means for applying said signal which passes through said first filter circuit to said first control circuit means; said expandor means further including a second filter circuit to which is applied the output signal from said compressor means, said second filter passing the signal only in said narrow frequency band, and means for applying said signal which passes through said second filter circuit to said second control circuit means.
Claim 18
Dependent Claim
42 words
The system as defined in claim 12 wherein said signal transmission system means comprises a recording medium, means for recording the output signal from said compressor means on said recording medium, and means for reproducing the recorded signal from said recording medium.
Claim 19
Dependent Claim
53 words
The apparatus as defined in claim 12 further comprising a filter circuit to which is applied the output signal from said compressor means, said filter circuit passing the signal only in said narrow frequency band, and means for applying said signal which passes through said filter circuit to said second control circuit means.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-09-03 | 1977-03-05 | 1977-09-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-03 | 1981-03-05 | 1981-09-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-03 | 1985-03-05 | 1985-09-04 | $7700.00 | Window Closed / Lapsed |