Noise cancellor
First Claim
1. A noise cancellor for canceling noise which is generated from a driving device and propagates to a predetermined object point, comprising:
- a first sensor for detecting the noise generated from the driving device and converting the noise to electric signals;
signal processing means for multiplying said electric signals by a predetermined factor series to form control signals;
sound producing means for producing, in response to said control signals, sound which interferes with the noise so as to cancel the noise at the object point; and
a second sensor for detecting sound at the object point, converting them to electric signals, and inputting them to the signal processing means;
said signal processing means including adaptive active control means for changing said factor series in response to the electric signals detected by said second sensor, and selecting means for selecting a first control mode wherein said adaptive active control means is used or a second control wherein said factor series is fixed, in accordance with a predetermined condition, until the electric signals from the second sensor have a value which falls within a predetermined range.
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Accused Products
Abstract
A noise cancellor includes a first sensor for detecting a noise generated from a driving device and converting the noise to electric signals. A signal processor receives the electric signals and forms control signals by multiplying the electric signals by a predetermined factor series. In response to the control signals, a speaker produces sound which interferes with the noise so as to cancel the noise at an object point. A second sensor detects sound at the object point and converts them to electric signals which are inputted to the signal processor. The signal processor switches the control mode, in accordance with a predetermined condition, to an adaptive active control wherein the factor series is changed in response to the electric signal applied from the second sensor or an active control wherein the factor series is fixed.
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Citations
26 Claims
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1. A noise cancellor for canceling noise which is generated from a driving device and propagates to a predetermined object point, comprising:
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a first sensor for detecting the noise generated from the driving device and converting the noise to electric signals; signal processing means for multiplying said electric signals by a predetermined factor series to form control signals; sound producing means for producing, in response to said control signals, sound which interferes with the noise so as to cancel the noise at the object point; and a second sensor for detecting sound at the object point, converting them to electric signals, and inputting them to the signal processing means; said signal processing means including adaptive active control means for changing said factor series in response to the electric signals detected by said second sensor, and selecting means for selecting a first control mode wherein said adaptive active control means is used or a second control wherein said factor series is fixed, in accordance with a predetermined condition, until the electric signals from the second sensor have a value which falls within a predetermined range. - View Dependent Claims (2, 3, 4, 5)
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6. A noise cancellor for canceling noise which is generated from a driving device and propagates to a predetermined object point comprising:
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a first sensor for detecting said noise generated from the driving device and converting the noise to electric signals; signal processing means for multiplying said electric signals by a predetermined factor series to form control signals; sounding means for producing, in response to said control signals, sound which interferes with said noise so as to cancel the noise at said object point; and a second sensor for detecting sound at said object point, converting said sound to electric signals, and inputting them to said signal processing means; said signal processing means including adaptive active control means for changing said factor series in response to said electric signals detected by said second sensor, and adjusting means for adjusting frequency of change of said factor series in accordance with a predetermined condition, until the electric signals from the second sensor have a value which falls within a predetermined range. - View Dependent Claims (7)
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8. A noise cancellor for canceling noise which is generated from a driving device and propagates to a predetermined object point, comprising:
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a first sensor for detecting said noise generated from the driving device and converting said noise to electric signals; signal processing means for multiplying said electric signals by a predetermined factor series to form control signals; sound producing means for producing, in response to said control signals, sound which interferes with said noise so as to cancel said noise at said object point; a second sensor for detecting sound at said object point, converting the sound to electric signals, and inputting them to said signal processing means; and a control unit for sending instructions of stop and restart of said driving device; said signal processing means including adaptive active control means for changing the present factor series in response to said electric signals detected by said second sensor, and output means for memorizing the present factor series when said output means receives said instruction of stop and for outputting, as an initial value, said factor series stored in said output means when said output means receives said instruction of restart.
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9. A noise cancellor for canceling noise which is generated from a driving device having a predetermined driving frequency and propagates to a predetermined object point, comprising:
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a sensor for detecting noise generated from said driving device and converting it to time series signals; signal processing means for storing impulse response functions responding to only specific frequencies based on the driving frequency of said driving device and for producing control signals by convoluting said time series signals by said impulse response functions; and sound producing means for producing, in response to said control signals, sound which interferes with said noise so as to cancel said noise at said object point. - View Dependent Claims (10, 11)
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12. A noise cancellor for canceling noise which is generated from a driving device having a predetermined driving frequency and propagates to a predetermined object point, comprising:
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a sensor for detecting noise generated from the driving device and converting it to time series signals; signal processing means for holding only components of transfer functions, which have specific frequencies based on said driving frequency of said driving device, converting the time series signals to frequency domain signals by means of Fourier transform, multiplying said frequency domain signals by said components of the transfer functions, and converting the resultant to time series control signals by means of inverse Fourier transform; and sound producing means for producing, in response to said time series control signals, sound which interferes with said noise so as to cancel said noise at the object point. - View Dependent Claims (13)
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14. A method of canceling noise which is generated from a driving device and propagates to an object point, comprising:
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a first converting step of detecting noise and converting it to electric signals; a producing step of producing control signals by multiplying said electric signals by a predetermined factor series; a canceling step of producing, in response to the control signals, sound which interferes with said noise so as to cancel said noise at the object point; and a second converting step of detecting sound at said object point to convert said sound to electric signals; said producing step including a selecting process of selecting adaptive active control wherein said factor series is changed in response to said electric signals converted by said second converting step or active control wherein said factor series is to be fixed, in accordance with a predetermined condition, until the electric signals from the second sensor have a value which falls within a predetermined range. - View Dependent Claims (15, 16, 17, 18)
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19. A method of canceling noise which is generated from a driving device and propagates to an object point, comprising:
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a first converting step of detecting noise and converting it to electric signals; a producing step of producing control signals by multiplying said electric signals by a predetermined factor series; a canceling step of producing, in response to the control signals, sound which interferes with said noise so as to cancel said noise at said object point; a second converting step of detecting sounds at said object point to convert said sound to electric signals; and a changing step of changing said factor series in response to said electric signals converted by said second converting step, said changing step including a process of adjusting the frequency of change of said factor series, in accordance with a predetermined condition, until the electric signals from the second sensor have a value which falls within a predetermined range. - View Dependent Claims (20)
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21. A method of canceling noise which is generated from a driving device and propagates to an object point, comprising:
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a converting step of detecting noise generated from said driving device and converting it to electric signals; a producing step of producing control signals by multiplying said electrical signals by a predetermined factor series; a canceling step of producing, in response to the control signals, sound which interferes with said noise to cancel said noise at the object point; a memorizing step of memorizing the present factor series when a stop instruction of said driving device is outputted; and an outputting step of outputting the stored factor series as an initial value when a restart instruction of said driving device is outputted.
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22. A method of canceling noise which is generated from a driving device having a predetermined driving frequency and propagates to an object point, comprising:
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a step of detecting noise generated from said driving device and converting it to time series signals; a step of producing control signals by convoluting said time series signals by impulse response functions which response to only specific frequencies based on said driving frequency of said driving device; and a step of producing, in response to the control signals, sound which interferes with said noise to cancel said noise at said object point. - View Dependent Claims (23, 24)
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25. A method of canceling noise which is generated from a driving device having a predetermined driving frequency and propagates to a predetermined object point, comprising:
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a converting step of detecting noise generated from the driving device and converting it to time series signals; a processing step of holding only components of transfer functions, which have specific frequencies based on said driving frequency of said driving device, converting the time series signals to frequency domain signals by means of Fourier transform, multiplying said frequency domain signals by said components of the transfer functions, and converting the resultant to time series control signals by means of inverse Fourier transform; and a canceling step of producing, in response to said time series control signals, sound which interferes with said noise so as to cancel said noise at the object point. - View Dependent Claims (26)
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Specification