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EP0615224A2
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A method of determining the sound transfer characteristic of an active noise control system
Assignee: Fujitsu Ltd
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Filing: 1993-09-03
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Granted: —
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Expires: 2013-09-03
Abstract
Abstract Method of determining a transfer characteristic in an active-noise-control system, comprises the steps of: arranging an error-detection means (25) for detecting a noise-cancelling effect, a speaker (26) for generating noise-cancelling sound, the detection means (25) and a speaker (26) being inwardly spaced by a given distance away from an end of a one-dimensional sound field that is defined by a linear ventilating system in which sound travels essentially parallel to the extended direction of the system (22), a noise detection means (23) in the vicinity of a noise source (21) in the one-dimensional sound field, and a transfer-characteristic-detection means (24) between the noise-detection means (23) and the error-detection means (25) in the one-dimensional sound field; supplying an output of the noise-detection means (23) to an adaptive filter that causes the speaker (26) to generate noise cancelling sound, the adaptive filter involving a filter (53) for preventing feedback sound according to an output of the error-detection means (25), a filter (61) for modeling a transfer system detection means, and a noise-cancelling filter (60) whose parameters are continuously adjusted; and activating a transfer-characteristic determining means, through a sequencer (58) when the noise detected by the error-detection means (25) is minimized, to determine the transfer function of the one-dimensional sound field according to outputs of the noise-detection means (23) and transfer-characteristic-detection means (24).
Inventors
- 👤 Tadashi C/O Fujitsu Limited Ohashi
- 👤 Kensaku C/O Fujitsu Limited Fujii
- 👤 Juro C/O Fujitsu Limited Ohga
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 08:44
CPC Classifications
G; G10; G10K; G10K11/00; G10K11/16; G10K11/175; G10K11/178; G10K11/1781; G10K11/17813; G10K11/17815; G10K11/1785; G10K11/17853; G10K11/17854; G10K11/1787; G10K11/17879; G10K11/17881; G10K2210/00; G10K2210/30; G10K2210/301; G10K2210/3018; G10K2210/3023; G10K2210/30232; G10K2210/3045; G10K2210/3049; G10K2210/50; G10K2210/506
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
229 words
A method of determining a transfer characteristic in an active-noise-control system, comprising the steps of: arranging an error-detection means (5) for detecting a noise-cancelling effect, a speaker (6) for generating noise-cancelling sound, the detection means (5) and a speaker (6) being inwardly spaced by a given distance away from an end of a one-dimensional sound field (2) that is defined by a linear ventilating system in which sound travels essentially parallel to the extended direction of the system, a noise detection means (3) in the vicinity of a noise source (1) in the one-dimensional sound field (2), and a transfer-characteristic-detection means (4) between the noise-detection means (3) and the error-detection means (5) in the one-dimensional sound field (2); supplying an output of the noise-detection means (3) to an adaptive filter (7) that causes the speaker (6) to generate noise cancelling sound, the adaptive filter (7) involving a filter for preventing feedback sound according to an output of the error-detection means (5), a filter for modeling a transfer system between the speaker and the error-detection means, and a noise- cancelling filter whose parameters are continuously adjusted; and activating a transfer-characteristic determining means (8), through a sequencer (9) when the noise detected by the error-detection means (5) is minimized, to determine the transfer function of the one-dimensional sound field according to outputs of the noise-detection means (3) and transfer-characteristic-detection means (4).
Claim 2
Independent Claim
136 words
A method of determining the transfer characteristic in an active-noise-control system, comprising the steps of: generating white noise at an end of a one-dimensional sound field that is defined by a linear ventilating system in which sound travels essentially parallel to the extended direction of the system; equalizing the transfer characteristic of the one-dimensional sound field and generating cancelling sound, according to an inverse of the transfer characteristic, to cancel the white noise and prevent noise being output from the other end of the one-dimensional sound field; continuously preventing the noise output and measuring the characteristic data of the one-dimensional sound field at, at least, one measuring point in the one-dimensional sound field; and calculating the transfer function of the one-dimensional sound field in the noise-output-prevented state, according to the characteristic data of the sound field.
Claim 3
Dependent Claim
23 words
The method according to claim 2, wherein the transfer characteristic of the one-dimensional sound field is equalized according to a learning identification method.
Claim 4
Dependent Claim
22 words
The method according to claim 2, wherein the transfer characteristic of the one-dimensional sound field is equalized according to an NLMS method.
Claim 5
Dependent Claim
24 words
The method according to claim 2, wherein the equalization of the transfer characteristic of the one-dimensional sound field involves the teaching a feedback-sound-preventive L-filter.
Claim 6
Dependent Claim
25 words
The method according to claim 2, wherein the equalization of the transfer characteristic of the one-dimensional sound field involves the teaching a noise cancelling D-filter.
Claim 7
Dependent Claim
45 words
The method according to claim 2, wherein the equalization of the transfer characteristic of the one-dimensional sound field involves the teaching a C-filter which models a transfer system between a speaker for generating noise cancelling sound and a microphone for detecting a noise cancelling effect.
Claim 8
Dependent Claim
29 words
The method according to claim 2, wherein the noise-output-prevented state is realized by fixing the parameters of the L- and C-filters and maintaining the adaptive operation of the D-filter.
Claim 9
Dependent Claim
51 words
The method according to claim 2, wherein the characteristic data of the one-dimensional sound field include signal-level data related to a noise-output measured at an end of the one-dimensional sound field and signal-level data related to the noise output measured at, at least, one measuring point in the one-dimensional sound field.
Claim 10
Dependent Claim
16 words
The method according to claim 9, wherein the signal level data are stored in a memory.
Claim 11
Dependent Claim
23 words
The method according to claim 2, wherein the at least one measuring point is sequentially shifted by a given distance at given intervals.
Claim 12
Dependent Claim
26 words
The method according to claim 2, wherein the measured data are subjected to reverse Fourier transformation to obtain the transfer function of the one-dimensional sound field.
Claim 13
Dependent Claim
26 words
The method according to claim 2, wherein an impulse response is obtained from the measured data when obtaining the transfer function of the one-dimensional sound field.
Claim 14
Dependent Claim
26 words
The method according to claim 2, wherein an auto-correlation function is obtained from the measured data when obtaining the transfer function of the one-dimensional sound field.
Claim 15
Dependent Claim
26 words
The method according to claim 2, wherein a cross-correlation function is obtained from the measurd data when obtaining the transfer function of the one-dimensional sound field.
Claim 16
Independent Claim
265 words
An apparatus for estimating a transfer characteristic in an active-noise-control system, comprising: noise detection means (3) disposed in the vicinity of a noise source (1), to detect white noise caused by the noise source (1) that is disposed at an end of a one-dimensional sound field (2) that is defined by a linear ventilating system in which sound travels essentially parallel to the extended direction of the system; error detection means (5) spaced away from the noise source (1) by a given distance and inwardly positioned away from an open end of the one-dimensional sound field (2) by a given distance; a speaker (6) disposed in the vicinity of the error detection means (5), to generate sound for cancelling the white noise; transfer characteristic detection means (4) disposed between the noise detection means (3) and the error detection means (5), to measure the transfer characteristic of the one-dimensional sound field (2); an adaptive filter (7) whose parameters are successively adjusted according to outputs from the noise detection means (3) and error detection means (5), to cause the speaker (6) to generate the noise cancelling sound; a sequencer (9) for starting the determination of a transfer characteristic when the cancelling sound provided by the speaker (6) cancels the noise and the error detection means (5) detects no noise, the sequencer maintaining the noise cancelled state until the determination is completed; and transfer characteristic determination means (8) for determining the transfer function of the one-dimensional sound field according to outputs of the noise-detection means (3) and transfer-characteristic-detection means (4), according to an instruction from the sequencer (9).
Claim 17
Dependent Claim
31 words
The apparatus according to claim 16, wherein the transfer-characteristic-detection means (4) is sequentially shifted by a given distance at given intervals between the noise-detection means (3) and the error-detection means (5).
Claim 18
Dependent Claim
19 words
The apparatus according to claim 16, wherein the sequencer (9) has a memory for storing the determined transfer-function data.
References Cited (Backward Citations)
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