US4805733A — Active silencer

Claim 1

Independent Claim 183 words

An active silencer provided at a pipe which has one end reaching a noise source and another end open, said active silencer comprising: means for generating a sound into said pipe so that a noise passing through said pipe from said noise source is reduced; means for collecting the sound dissipated from the open end of the pipe, said sound collecting means being provided outside the pipe close to said another open end and away from said sound generating means; means connected to said sound collecting means for generating a lead phase output signal by leading a phase of an output signal of said sound collecting means by a phase substantially corresponding to a predetermined time τ, said predetermined time τ being set so that τ=L/C, wherein L is a distance between said sound generating means and said sound collecting means and C is the speed of sound; and means connected to said phase leading means for outputting a drive signal which is an inverted signal of said lead phase output signal and for driving said sound generating means by said drive signal.

Claim 2

Dependent Claim 183 words

An active silencer provided at a pipe which has one end reaching a noise source and another end open, said active silencer comprising: means for generating a sound into said pipe so that a noise passing through said pipe from said noise source is reduced; means for collecting the sound dissipated from the open end of the pipe, said sound collecting means being provided outside the pipe close to said another open end and away from said sound generating means; means connected to said sound collecting means for generating a lead phase output signal by leading a phase of an output signal of said sound collecting means by a phase substantially corresponding to a predetermined time τ, said predetermined time τ being set so that τ=L/C, wherein L is a distance between said sound generating means and said sound collecting means and C is the speed of sound; and means connected to said phase leading means for outputting a drive signal which is an inverted signal of said lead phase output signal and for driving said sound generating means by said drive signal.

Claim 3

Dependent Claim 31 words

An active silencer according to claim 1, wherein use is made of a speaker as said sound generating means and use is made of a microphone as said sound collecting means.

Claim 4

Dependent Claim 113 words

At active silencer according to claim 1, wherein said phase leading means is provided with a phase comparison circuit, a voltage controlled oscillation circuit which outputs an oscillating signal of a frequency proportional to the input voltage, and a delay circuit with a delay time set to said predetermined time, wherein part of said oscillating signal is input to said delay circuit, an output signal of said sound collecting means and an output signal of said delay circuit are input to said phase comparison circuit, and an output of said phase comparison circuit is input to said voltage controlled oscillation circuit, whereby said oscillating signal is used as said lead phase output signal.

Claim 5

Dependent Claim 28 words

An active silencer according to claim 3, wherein said phase comparison circuit issues an output signal in accordance with a phase difference detected by said phase comparison circuit.

Claim 6

Dependent Claim 49 words

An active silencer according to claim 4, wherein said phase comparison circuit issues a predetermined reference voltage when said detected phase difference is zero and issues a voltage which changes over a predetermined voltage range about said reference voltage when said detected phase difference changes from -π/2 to π/2.

Claim 7

Dependent Claim 25 words

An active silencer according to claim 3, wherein a low pass filter is connected between said phase comparison circuit and said voltage controlled oscillation circuit.

Claim 8

Dependent Claim 24 words

An active silencer according to claim 3, wherein a band pass filter is connected between said voltage controlled oscillation circuit and said delay circuit.

Claim 9

Dependent Claim 37 words

An active silencer according to claim 7, wherein said band pass filter is constituted by converter means for converting a sawtooth wave output of said voltage controlled oscillation circuit into a sine wave of the same frequency.

Claim 10

Dependent Claim 71 words

An active silencer according to claim 3, wherein said drive signal outputting means is provided with a voltage controlled amplification circuit, whose gain changes in accordances with the input voltage, and a phase inversion circuit, said voltage controlled amplification circuit amplifying said lead phase output signal input thereto with a gain corresponding to the output of said phase comparison circuit and supplying said amplified output signal to said phase inversion circuit.

Claim 11

Dependent Claim 35 words

An active silencer according to claim 9, wherein said voltage controlled amplification circuit amplifies said lead phase output signal with a maximum gain when a phase difference detected by said phase comparison circuit is zero.

Claim 12

Dependent Claim 50 words

An active silencer according to claim 9, further provided with a mixer which adds the output signals of a plurality of voltage controlled amplification circuits receiving as input lead phase output signals of respective, differing frequency ranges, the output signal of said mixer being supplied to said phase inversion circuit.

Claim 13

Dependent Claim 65 words

An active silencer according to claim 11, wherein a plurality of said phase leading means is provided, said phase leading means receiving as input from said sound collecting means only the output signals of respective, predetermined frequency ranges, each of the lead phase output signals output from said plurality of phase leading means being input into each of said plurality of voltage controlled amplification circuits.

Claim 14

Dependent Claim 30 words

An active silencer according to claim 12, further provided with a band pass filter which takes into a predetermined phase leading means only output signals of said predetermined frequency range.

Claim 15

Dependent Claim 257 words

An active silencer provided at a pipe which has one end reaching a noise source and another end reaching the atmosphere, said active silencer comprising: means for generating a sound into said pipe so that a noise passing through said pipe from said noise source is reduced; means for collecting the sound passing through said pipe from said sound generating means, said sound collecting means being provided at a position further away from said noise source than said sound generating means; means connected to said sound collecting means for generating a lead phase output signal by leading a phase of an output signal of said sound collecting means by a phase substantially corresponding to a time determined by a distance between said sound generating means and sound collecting means, comprising: means for comparing a phase of said output signal of said sound collecting means with that of a delay signal produced by delaying said lead phase output signal, means for oscillating said lead phase output signal according to an output signal of said phase comparing means, a frequency of said lead phase output signal being proportional to said output signal of said phase comparing means, and means for delaying said lead phase output signal, wherein said phase comparing means, said oscillating means, and said delay means constitute a phase locked loop; and means responsive to said lead phase output signal for outputting a drive signal which is an inverted signal of said lead phase output signal and for driving said sound generating means by said drive signal.

Claim 16

Dependent Claim 257 words

An active silencer provided at a pipe which has one end reaching a noise source and another end reaching the atmosphere, said active silencer comprising: means for generating a sound into said pipe so that a noise passing through said pipe from said noise source is reduced; means for collecting the sound passing through said pipe from said sound generating means, said sound collecting means being provided at a position further away from said noise source than said sound generating means; means connected to said sound collecting means for generating a lead phase output signal by leading a phase of an output signal of said sound collecting means by a phase substantially corresponding to a time determined by a distance between said sound generating means and sound collecting means, comprising: means for comparing a phase of said output signal of said sound collecting means with that of a delay signal produced by delaying said lead phase output signal, means for oscillating said lead phase output signal according to an output signal of said phase comparing means, a frequency of said lead phase output signal being proportional to said output signal of said phase comparing means, and means for delaying said lead phase output signal, wherein said phase comparing means, said oscillating means, and said delay means constitute a phase locked loop; and means responsive to said lead phase output signal for outputting a drive signal which is an inverted signal of said lead phase output signal and for driving said sound generating means by said drive signal.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1992-02-21	1992-08-22	1993-02-21	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1996-02-21	1996-08-22	1997-02-21	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2000-02-21	2000-08-22	2001-02-21	$7700.00	Window Closed / Lapsed

Active silencer

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