US3784749A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Noise eliminating device
Assignee: Kenwood KK
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Filing: 1972-02-09
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Granted: 1974-01-08
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Expires: 1992-02-09
Abstract
Abstract In a noise reducing device for reducing noises contained in audio signals, a frequency band wherein noises contained in audio signals are highly sensible to an auditor, but the frequency of appearance therein of the audio signals is substantially low is blocked by a required number of band-elimination filters provided in series in a transmission line for transmitting the audio signals, each of the band-elimination filters being bypassed by a corresponding variable impedance circuit, while the same frequency band is passed through a corresponding number of bandpass filters, the outputs of said band-pass filters being supplied respectively to corresponding control signal producing circuits to produce control signals, whereby said variable impedance circuits bypassing the band-elimination filters are controlled respectively by said control signals, and the bandelimination filters are thereby brought into a state effectively blocking the frequency band when the input audio signal level in said frequency band is lower than a predetermined value and vice versa.
Inventors
- 👤 K Kondo
- 👤 S Shigeyama
- 👤 Y Yamada
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 18:29
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/24; H; H03; H03G; H03G9/00; H03G9/02; H03G9/12; H03G9/18
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
125 words
A noise reducing device comprising: a. a transmission line for transmitting audio signals; b. a band-elimination filter provided in said transmission line for blocking a predetermined frequency band wherein noises are contained in the audio signals; c. a variable impedance shunting circuit connected in parallel with said band-elimination filter for conducting the audio signals therethrough the output of said band-elimination filter and said variable impedance circuit being combined; d. a band-pass filter provided in said transmission line for receiving part of the audio signals and passing the same frequency band thus blocked by said band-elimination filter; and e. a control signal producing circuit for producing a control signal out of the output of said band-pass filter for controlling the impedance of said variable impedance circuit.
Claim 2
Dependent Claim
125 words
A noise reducing device comprising: a. a transmission line for transmitting audio signals; b. a band-elimination filter provided in said transmission line for blocking a predetermined frequency band wherein noises are contained in the audio signals; c. a variable impedance shunting circuit connected in parallel with said band-elimination filter for conducting the audio signals therethrough the output of said band-elimination filter and said variable impedance circuit being combined; d. a band-pass filter provided in said transmission line for receiving part of the audio signals and passing the same frequency band thus blocked by said band-elimination filter; and e. a control signal producing circuit for producing a control signal out of the output of said band-pass filter for controlling the impedance of said variable impedance circuit.
Claim 3
Dependent Claim
57 words
A device as defined in claim 1, wherein said control signal is produced when the level of signals from the band-pass filter is below a predetermined value, said control signal increasing the impedance of said variable impedance shunting circuit whereby a larger portion of said audio signals are passed through said band-elimination filter increasing the effectiveness thereof.
Claim 4
Dependent Claim
156 words
A noise reducing device for reducing noises contained in audio signals, which comprises: a. a transmission line for transmitting audio signals; b. a buffer amplifier provided at the input side of said transmission line; c. a band-elimination filter provided at the output side of said buffer amplifier for blocking a predetermined frequency band wherein noises are contained in the audio signals; d. a variable impedance shunting circuit connected in parallel with said band-elimination filter for conducting the audio signal therethrough, the output of said band-elimination filter and said variable impedance circuit being combined; e. a band-pass filter provided at the output side of said buffer amplifier for receiving a part of the output thereof and passing the frequency band equal to that blocked by the band-elimination filter; and f. a control signal producing circuit for rectifying the output of said band-pass filter and producing a control signal for controlling the impedance of said variable impedance circuit.
Claim 5
Dependent Claim
156 words
A noise reducing device for reducing noises contained in audio signals, which comprises: a. a transmission line for transmitting audio signals; b. a buffer amplifier provided at the input side of said transmission line; c. a band-elimination filter provided at the output side of said buffer amplifier for blocking a predetermined frequency band wherein noises are contained in the audio signals; d. a variable impedance shunting circuit connected in parallel with said band-elimination filter for conducting the audio signal therethrough, the output of said band-elimination filter and said variable impedance circuit being combined; e. a band-pass filter provided at the output side of said buffer amplifier for receiving a part of the output thereof and passing the frequency band equal to that blocked by the band-elimination filter; and f. a control signal producing circuit for rectifying the output of said band-pass filter and producing a control signal for controlling the impedance of said variable impedance circuit.
Claim 6
Dependent Claim
57 words
A device as defined in claim 3, wherein said control signal is produced when the level of signals from the band-pass filter is below a predetermined value, said control signal increasing the impedance of said variable impedance shunting circuit whereby a larger portion of said audio signals are passed through said band-elimination filter increasing the effectiveness thereof.
Claim 7
Dependent Claim
193 words
A noise reducing device for reducing noises contained in audio signals comprising: a. a transmission line for transmitting the audio signals; b. a band-elimination filter provided in said transmission line for blocking a frequency band wherein noises are highly sensible to an auditor; c. a variable impedance shunting circuit connected in parallel with said band-elimination filter for conducting the audio signals therethrough, the output of said band-elimination filter and said variable impedance circuit beinG combined; d. a band-pass filter receiving a part of the audio signals and passing the same frequency band thus blocked by said band-elimination filter; e. a variable resistor for varying the output of said band-pass filter and adjusting the noise-reducing level of this device; f. a control signal producing circuit for rectifying the output of said variable resistor connected to said band-pass filter to obtain control signals for controlling the impedance of said variable impedance circuit; and g. another variable resistor interlinked with said first variable resistor for adjusting the input level of an indicating circuit and connected to receive the audio signals from the transmission line for amplifying and indicating the input level of the amplified audio signals.
Claim 8
Dependent Claim
193 words
A noise reducing device for reducing noises contained in audio signals comprising: a. a transmission line for transmitting the audio signals; b. a band-elimination filter provided in said transmission line for blocking a frequency band wherein noises are highly sensible to an auditor; c. a variable impedance shunting circuit connected in parallel with said band-elimination filter for conducting the audio signals therethrough, the output of said band-elimination filter and said variable impedance circuit beinG combined; d. a band-pass filter receiving a part of the audio signals and passing the same frequency band thus blocked by said band-elimination filter; e. a variable resistor for varying the output of said band-pass filter and adjusting the noise-reducing level of this device; f. a control signal producing circuit for rectifying the output of said variable resistor connected to said band-pass filter to obtain control signals for controlling the impedance of said variable impedance circuit; and g. another variable resistor interlinked with said first variable resistor for adjusting the input level of an indicating circuit and connected to receive the audio signals from the transmission line for amplifying and indicating the input level of the amplified audio signals.
Claim 9
Dependent Claim
57 words
A device as defined in claim 5, wherein said control signals are produced when the level of signals from the band-pass filter is below a predetermined value, said control signals increasing the impedance of said variable impedance shunting circuit whereby a larger portion of said audio signals are passed through said band-elimination filter increasing the effectiveness thereof.
Claim 10
Dependent Claim
181 words
A noise reducing device for reducing noise contained in audio signals comprising: a. a transmission line for transmitting to the audio signals; b. a buffer amplifier provided at the input side of said transmission line; c. at least two band-elimination filters provided in series at the output side of said buffer amplifier for blocking respectively two divided portions of a predetermined frequency band wherein noises are contained in the audio signals; d. a variable impedance shunting circuit connected in parallel with each of said band-elimination filters for conducting the audio signals therethrough, the output of said band-elimination filters and said variable impedance circuits being combined; e. at least two-band-pass filters for receiving a part of the output of said buffer amplifier and passing the frequency band blocked by said band-elimination filter; and f. a control signal producing circuit for rectifying the outputs of said band-pass filters separately for obtaining control signals which control the impedance of said variable impedance circuits connected in parallel with said band-elimination filters corresponding to those band-pass filters from which the outputs are obtained for the rectification.
Claim 11
Dependent Claim
181 words
A noise reducing device for reducing noise contained in audio signals comprising: a. a transmission line for transmitting to the audio signals; b. a buffer amplifier provided at the input side of said transmission line; c. at least two band-elimination filters provided in series at the output side of said buffer amplifier for blocking respectively two divided portions of a predetermined frequency band wherein noises are contained in the audio signals; d. a variable impedance shunting circuit connected in parallel with each of said band-elimination filters for conducting the audio signals therethrough, the output of said band-elimination filters and said variable impedance circuits being combined; e. at least two-band-pass filters for receiving a part of the output of said buffer amplifier and passing the frequency band blocked by said band-elimination filter; and f. a control signal producing circuit for rectifying the outputs of said band-pass filters separately for obtaining control signals which control the impedance of said variable impedance circuits connected in parallel with said band-elimination filters corresponding to those band-pass filters from which the outputs are obtained for the rectification.
Claim 12
Dependent Claim
57 words
A device as defined in claim 7, wherein said control signals are produced when the level of signals from the band-pass filters is below a predetermined value, said control signals increasing the impedance of said variable impedance shunting circuit whereby a larger portion of said audio signals are passed through said band-elimination filters increasing the effectiveness thereof.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-01-07 | 1977-07-09 | 1978-01-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-07 | 1981-07-09 | 1982-01-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-07 | 1985-07-09 | 1986-01-08 | $7700.00 | Window Closed / Lapsed |