Noise cancellor

Claim 2

A noise cancellor for canceling noise which is generated from a driving device and propagates to a predetermined object point, comprising: a first sensor (22) for detecting noise generated from the driving device (10) and converting the noise to electric signals; signal processing means (25) for multiplying said electric signals by a predetermined factor series to form control signals; sound producing means (30) for producing, in response to said control signals, sound which interferes with the noise so as to cancel the noise at the object point (13); and a second sensor (26) for detecting sound at the object point, converting them to electric signals, and inputting them to the signal processing means; characterized in that: said signal processing means (25) includes adaptive active control means for changing said factor series in response to the electric signals detected by said second sensor (26), 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.

Claim 3

A noise cancellor according to claim 1, characterized in that said selecting means includes means for determining the frequency of change from said second control mode to said first control mode, in accordance with a difference between the present factor series and a factor series of last time.

Claim 4

A noise cancellor according to claim 1, characterized in that wherein said selecting means has means for determining the frequency of change from said second control mode to said first control mode, in accordance with a lapsed time after the driving device is started.

Claim 5

A noise cancellor according to claim 1, charac­terized in that said selecting means has means for determining the frequency of change from said second control mode to said first control mode, in accordance with an operating condition of the driving device (10) or transfer functions around the driving device.

Claim 6

A noise cancellor according to claim 1, charac­terized by further comprising a control unit (31) for sending instructions of stop and restart of the driving device (10) to the signal processing means (25), and characterized in that said signal processing means includes output means for memorizing the present factor series when said signal processing means receives the instruction of stop and for outputting the memorized factor series as an initial value when said signal proc­essing means receives the instruction of restart.

Claim 7

A noise cancellor for canceling noise which is generated from a driving device and propagates to a predetermined object point comprising: a first sensor (22) for detecting noise generated from the driving device (10) and converting the noise to electric signals; signal processing means (25) for multiplying said electric signals by a predetermined factor series to form control signals; sound producing means (30) 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 (26) for detecting sound at said object point (13), converting said sound to electric signals, and inputting them to said signal processing means; characterized in that: said signal processing means (25) includes 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.

Claim 8

A noise cancellor for canceling noise which is generated from a driving device and propagates to a predetermined object point comprising: a first sensor (22) for detecting noise generated from the driving device (10) and converting the noise to electric signals; signal processing means (25) for multiplying said electric signals by a predetermined factor series to form control signals; sound producing means (30) 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 (26) for detecting sound at said object point (13), converting said sound to electric signals, and inputting them to said signal processing means; characterized in that: said signal processing means (25) includes 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.

Claim 9

A noise cancellor according to claim 6, characterized in that said adjusting means has means for determining whether said factor series should be changed, based on the following expression: ( | h m - h m-1 | ) N > ε, where h m is a factor series set last time, h m-1 is a factor series set just before last time, N is a number for determination, and ε is a constant.

Claim 10

A noise cancellor for canceling noise which is generated from a driving device and propagates to a predetermined object point, comprising: a first sensor (22) for detecting said noise gener­ated from the driving device (10) and converting said noise to electric signals; signal processing means (25) for multiplying said electric signals by a predetermined factor series to form control signals; sound producing means (30) for producing, in response to said control signals, sound which interferes with said noise so as to cancel said noise at said object point (13); a second sensor (26) 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 (31) for sending instructions of stop and restart of said driving device; characterized in that: said signal processing means (25) includes 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.

Claim 11

A noise cancellor for canceling noise which is generated from a driving device and propagates to a predetermined object point, comprising: a first sensor (22) for detecting said noise gener­ated from the driving device (10) and converting said noise to electric signals; signal processing means (25) for multiplying said electric signals by a predetermined factor series to form control signals; sound producing means (30) for producing, in response to said control signals, sound which interferes with said noise so as to cancel said noise at said object point (13); a second sensor (26) 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 (31) for sending instructions of stop and restart of said driving device; characterized in that: said signal processing means (25) includes 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.

Claim 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: a sensor (22) for detecting noise generated from said driving device (10) and converting it to time series signals; signal processing means (25) for producing control signals in response to said time series signals; and sound producing means (30) for producing, in response to said control signals, sound which interferes with said noise so as to cancel said noise at said object point (13); characterized in that: said signal processing means (25) stores impulse response functions responding to only specific frequen­cies based on the driving frequency of said driving device (10), and produces control signals by convoluting said time series signals by said impulse response functions.

Claim 13

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: a sensor (22) for detecting noise generated from said driving device (10) and converting it to time series signals; signal processing means (25) for producing control signals in response to said time series signals; and sound producing means (30) for producing, in response to said control signals, sound which interferes with said noise so as to cancel said noise at said object point (13); characterized in that: said signal processing means (25) stores impulse response functions responding to only specific frequen­cies based on the driving frequency of said driving device (10), and produces control signals by convoluting said time series signals by said impulse response functions.

Claim 14

A noise cancellor according to claim 9, characterized in that said impulse response functions are obtained by means of inverse Fourier transform of components of transfer functions which correspond to said driving frequency and integral multiples thereof.

Claim 15

A noise cancellor according to claim 9, characterized in that said impulse response functions are obtained by means of inverse Fourier transform of transfer functions, which have frequencies falling within ranges over which said driving frequency and integral multiples thereof are allowed to change.

Claim 16

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: a sensor (2) for detecting noise generated from the driving device (10) and converting it to time series signals; signal processing means (25) for producing control signals in response to said time series signals; and sound producing means (30) for producing, in response to said time series control signal, sound which interferes with said noise so as to cancel said noise at the object point (13); characterized in that: said signal processing means (25) holds only compo­nents of transfer functions, which have specific fre­quencies based on said driving frequency of said driving device, convertes the time series signals to frequency domain signals by means of Fourier transform, multiplies said frequency domain signals by said components of the transfer functions, and convertes the resultant to time series control signals by means of inverse Fourier transform.

Claim 17

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: a sensor (2) for detecting noise generated from the driving device (10) and converting it to time series signals; signal processing means (25) for producing control signals in response to said time series signals; and sound producing means (30) for producing, in response to said time series control signal, sound which interferes with said noise so as to cancel said noise at the object point (13); characterized in that: said signal processing means (25) holds only compo­nents of transfer functions, which have specific fre­quencies based on said driving frequency of said driving device, convertes the time series signals to frequency domain signals by means of Fourier transform, multiplies said frequency domain signals by said components of the transfer functions, and convertes the resultant to time series control signals by means of inverse Fourier transform.

Claim 18

A noise cancellor according to claim 12, characterized in that said components of said transfer functions include components corresponding to said driv­ing frequency, integral multiples thereof and predeter­mined frequency ranges over which said driving frequency and integral multiples thereof are allowed to change.

Claim 21

A method according to claim 14, characterized in that said selecting step includes a process of deter­mining the frequency of change from said active control to said adaptive active control, in response to a dif­ference between the present factor series and a factor series of last time.

Claim 22

A method according to claim 15, characterized in that said selecting step includes a process of deter­mining the frequency of change from said active control to said adaptive active control in response to a lapsed time after the driving device (10) is started.

Claim 23

A method according to claim 14, characterized in that said selecting step includes a process of deter­mining the frequency of change from said active control to said adaptive active control, in accordance with an operating condition of the driving device (10) or trans­fer functions around the driving device.

Claim 24

A method according to claim 14, characterized in that said producing step includes a first process of memorizing the present factor series when a stop instruction of said driving device (10) is output and a second process of outputting, as an initial value, the memorized factor series when a restart instruction of said driving device is output.

Claim 27

The method according to claim 19, character­ized in that said frequency of change of said factor series is determined by the following expression: ( | h m - h m-1 | ) N > ε, where hm is a factor series of last time, h m-1 is a fac­tor series from which said factor series of last time was changed, N is a number for determination and ε is a constant.

Claim 32

A method according to claim 22, characterized in that said impulse response functions are obtained by means of inverse Fourier transform of components of transfer functions which correspond to said driving fre­quency and integral multiples thereof.

Claim 33

A method according to claim 22, characterized in that said impulse response functions are obtained by means of inverse Fourier transform of transfer func­tions, which have frequencies falling within ranges over which said driving frequency and said integral multiples thereof are allowed to change.

Claim 36

A method according to claim 25, characterized in that said components of said transfer functions include components corresponding to said driving frequency, integral multiples thereof and predetermined frequency ranges over which said driving frequency and integral multiples thereof are allowed to change.