Apparatus for reducing noise in a closed space having divergence detector

• US 5,809,152 A
• Filed: 10/10/1996
• Issued: 09/15/1998
• Est. Priority Date: 07/11/1991
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd., Nissan Motor Co., Ltd.
• Original Assignee: Hitachi, Ltd., Nissan Motor Co., Ltd.
• Inventors: Hasegawa, Satoshi, Tabata, Toshiyuki, Saito, Hiroyuki, Nakamura, Mitsuru, Sasaki, Mitsuhide, Sato, Noriharu
• Primary Examiner(s): Kuntz, Curtis A.
• Assistant Examiner(s): LEE, PING
• Application Number:
  US08/728,640
• Time in Patent Office: 705 Days
• Field of Search: 381/71.4, 381/71.8, 381/71.11, 381/71.12, 381/71.1, 381/94.1
• US Class Current: 381/71.8
• CPC Class Codes: G10K 11/17825 Error signals
• CPC Class Codes: G10K 11/17833 by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17883 the reference signal being derived from a machine operating condition, e.g. engine RPM or vehicle speed
• CPC Class Codes: G10K 2210/121 Rotating machines, e.g. engines, turbines, motors; Periodic or quasi-periodic signals in general
• CPC Class Codes: G10K 2210/128 Vehicles
• CPC Class Codes: G10K 2210/3026 Feedback
• CPC Class Codes: G10K 2210/3027 Feedforward
• CPC Class Codes: G10K 2210/503 Diagnostics; Stability; Alarms; Failsafe
• CPC Class Codes: G10K 2210/511 Narrow band, e.g. implementations for single frequency cancellation

Abstract

An automatic sound suppression system is automatically disengaged whenever noise in an area and generated counter noise deviate in their reverse phase relationship or if the amplitude of the counter noise deviates from that of the noise. The system can also be automatically disengaged whenever divergence prediction means predicts that sounds of the noise and the counter noise diverge or whenever divergence prediction means predict that sounds of the noise and the counter noise are about to diverge. The system can also operate as a vibration reducing apparatus which is also automatically disengaged whenever divergence prediction means predicts that a vibration and a generated countervibration diverge.

Claims

1. A noise-reducing apparatus, comprising:

noise detection means for detecting noises generated by propagation of mechanical vibration;

arithmetic means for calculating a signal to produce secondary sounds of reverse phase to the noises in terms of frequencies of the vibrations;

secondary sound generating means for generating the secondary sounds based on the signal calculated by the arithmetic means to reduce the noises;

means for monitoring values of the signal univocally determined by adaptive filter coefficients used by the arithmetic means to calculate the signal; and

means for automatically interrupting the signal before the generation of the secondary sounds if the noises and the secondary sounds at positions of the noise detection means are predicted to deviate in their reverse phase relationship or if amplitudes of the secondary sounds are predicted to deviate from amplitudes of the noises, as determined by said means for monitoring.

2. A noise-reducing apparatus, comprising:

noise detection means for detecting noises generated by propagation of mechanical vibration;

arithmetic means for calculating a signal to produce secondary sounds of reverse phase to the noises in terms of frequencies of the vibrations;

secondary sound generating means for generating the secondary sounds based on the signal calculated by the arithmetic means to reduce the noises;

means for monitoring values of the signal univocally determined by adaptive filter coefficients used by the arithmetic means to calculate the signal; and

means for automatically interrupting the signal before the generation of the secondary sounds if remaining sounds of the noises and the secondary sounds at positions of the noise detection means are predicted to increase, as determined by said means for monitoring values.

3. A noise-reducing apparatus, comprising:

control means for reducing noises generated by propagation of mechanical vibration by actively canceling the noises out with secondary sounds generated by a signal calculated in terms of frequencies of the mechanical vibrations;

divergence prediction means for monitoring values of the signal univocally determined by filter coefficients used by the control means and predicting whether remaining sounds of the noises and the secondary sounds will diverge or not based on the monitored values; and

function interruption means for automatically interrupting the signal and function of the control means if the divergence prediction means predicts a divergence.

5. A noise-reducing apparatus according to claim 3, wherein the divergence prediction means further includes means for monitoring sound pressures of the remaining sounds to predict whether the remaining sounds will diverge or not based on the monitored values and the monitored sound pressures.

4. A noise-reducing apparatus, comprising:

control means for reducing noises generated by propagation of mechanical vibration by actively canceling the noises out with secondary sounds generated by a signal calculated in terms of frequencies of the mechanical vibrations;

divergence prediction means for monitoring values of the signal functionally related to filter coefficients used by the control means and predicting whether remaining sounds of the noises and the secondary sounds will diverge or not based on the monitored values;

function interruption means for automatically interrupting the signal and function of the control means if the divergence prediction means predicts a divergence; and

wherein the control means generates the signal as an output of an adaptive digital filter, and the divergence prediction means monitors coefficient values of the adaptive digital filter used to produce the signal to predict whether the remaining sounds will diverge or not.

6. A noise-reducing apparatus, comprising:

control means for reducing noises generated by propagation of mechanical vibration by actively canceling the noises out with secondary sounds generated as calculated in terms of frequencies of the mechanical vibrations;

divergence prediction means for monitoring values functionally related to filter coefficients used by the control means and predicting whether remaining sounds of the noises and the secondary sounds will diverge or not based on the monitored values;

function interruption means for automatically interrupting function of the control means if the divergence prediction means predicts a divergence; and

wherein said monitored values include secondary sound signals fed to a secondary sound generating actuator provided in the control means.

7. Vibration-reducing apparatus, comprising:

control means for reducing mechanical vibrations propagated from a vibration source by canceling the mechanical vibrations out with secondary vibrations generated by a signal calculated in terms of frequencies of the mechanical vibrations;

divergence prediction means for monitoring values of the signal univocally determined by filter coefficients used by the control means and predicting whether synthesized vibrations of the propagated mechanical vibrations and the secondary vibrations will diverge or not based on the monitored values; and

function interruption means for automatically interrupting the signal and function of the control means if the divergence prediction means predicts a divergence.

8. A noise control system, comprising:

a noise detector for detecting noise;

a counter noise generator for generating a signal to produce counter noise to reduce at least a portion of the noise detected by the noise detector, the counter noise generator including a filter with adaptive filter coefficients;

a noise divergence predictor for monitoring values of the signal univocally determined by the filter coefficients and predicting a future divergence condition with the counter noise generator contributing undesirable noise based on the monitored values; and

a controller for limiting the signal before the generation of the counter noise by the counter noise generator in response to the noise divergence predictor predicting a future divergence condition.

9. A noise control system according to claim 8, wherein said controller includes a control switch for shutting off the signal from the counter noise generator in response to the noise divergence predictor predicting a future divergence condition.

10. A noise control system according to claim 8, wherein the counter noise generator includes apparatus for controlling the phase and amplitude of the counter noise being generated as a predetermined function of the phase and amplitude of the noise detected by the noise detector.

11. A noise control system according to claim 8, wherein the noise divergence predictor includes apparatus for predicting a divergence as a predetermined function of the phase and amplitude of the noise detected by the noise detector.

12. A noise control system according to claim 8, wherein the noise detector and counter noise generator are disposed in a passenger compartment of a combustion engine driven vehicle, with the passenger compartment subjected to engine induced mechanical vibrations causing the noise detected at the noise detector.

13. A noise control system according to claim 8, wherein the noise detector and counter noise generator are disposed in a passenger compartment of a combustion engine driven vehicle, with the passenger compartment subjected to sound generated by sound generation means, said sound being detected by the noise detector.

14. The noise control system of claim 8, wherein the controller automatically limits the generation of noise by the counter noise generator in response to the noise divergence predictor predicting a future divergence condition.

15. A noise control system for controlling sound in an occupant compartment comprising:

a noise detector for detecting noise;

a counter noise generator for generating a signal to produce counter noise to reduce at least a portion of the noise detected by the noise detector, the counter noise generator including a filter with adaptive filter coefficients;

a noise divergence predictor for monitoring values of the signal univocally determined by the filter coefficients and predicting a future divergence condition with the counter noise generator contributing undesirable noise based on the monitored values; and

a controller for limiting the signal before the generation of noise by the counter noise generator in response to the noise divergence predictor predicting a future divergence condition.

16. A method of controlling noise in an occupant compartment of a combustion engine driven vehicle, with mechanical vibration induced noise occurring in the occupant compartment, comprising:

detecting noise in the occupant compartment at a predetermined detector location;

generating a signal to produce counter noise to reduce at least a portion of the noise of the occupant compartment by a counter noise speaker spaced from the detector location, the counter noise generator including a filter with adaptive filter coefficients;

predicting a future divergence condition in the occupant compartment during which the counter noise speaker contributes undesirable noise by monitoring values of the signal univocally determined by the filter coefficients; and

automatically limiting the signal before the generation of noise by the counter noise speaker in response to the predicting of a future divergence condition.

17. In a method of reducing undesirable noise by generating a signal to produce counter noise, the step of automatically interrupting the signal before the generation of the counter noise whenever the counter noise increases the amount of undesirable noise as determined by monitoring values of the signal univocally determined by adaptive filter coefficients used in the generation of the counter noise, thereby eliminating counter noise which contributes to undesirable noise.

18. In a method of reducing undesirable noise by generating a signal to produce counter noise, the step of automatically interrupting the signal before the generation of the counter noise whenever the counter noise is about to increase the amount of undesirable noise, as determined by monitoring values of the signal univocally determined by adaptive filter coefficients used in the generation of the counter noise, thereby eliminating counter noise which contributes to undesirable noise.

19. A noise-reducing apparatus comprising:

detecting means for detecting a sound pressure of noise;

controlling means for determining an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

at least one loudspeaker for generating the secondary sound;

means for detecting output power of the signal, said output power being proportional to the level of a magnitude of the secondary sound generated from said loudspeaker;

means for discriminating whether or not the detected output power is higher than that of a predetermined threshold; and

means for determining that an undesirable phenomenon of abnormal noise increase is occurring when the detected output power continues to exceed that of said threshold for at least a predetermined period of time, thereby to stop generating said secondary sound from said loudspeaker.

20. A noise-reducing apparatus comprising:

detecting means for detecting a sound pressure of noise;

controlling means for determining an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

at least one loudspeaker for generating the secondary sound;

means for detecting output power of the signal, said output power being proportional to the level of a magnitude of said secondary sound generated from said loudspeaker;

means for discriminating whether or not the detected output power is higher than that of a predetermined threshold;

means for adding together time periods for which the detected output power exceeds that of said threshold; and

means for determining that an undesirable phenomenon of abnormal noise increase is occurring when the value of the time periods added by said adding means exceeds a predetermined value, thereby to stop generating said secondary sound from said loudspeaker.

21. A noise-reducing apparatus comprising:

detecting means for detecting a sound pressure of noise;

controlling means for determining an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

at least one loudspeaker for generating the secondary sound;

means for detecting output power of the signal, said output power being proportional to the level of a magnitude of the secondary sound generated from said loudspeaker;

means for discriminating whether or not the detected output power is higher than that of a predetermined threshold;

means for adding together time periods for which the detected output power is higher than that of said threshold; and

means for determining that an undesirable phenomenon of abnormal noise increase is occurring when the ratio of the value of the time periods added by said adding means to a predetermined fixed period of time is more than a predetermined value, thereby to stop generating said secondary sound from said loudspeaker.

22. A noise-reducing apparatus comprising:

detecting means for detecting a sound pressure of noise;

controlling means for determining an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

at least one loudspeaker for generating the secondary sound;

means for sampling with a predetermined sampling period output power of the signal, said output power being proportional to the level of a magnitude of the secondary sound generated from said loudspeaker;

means for counting the number of times the detected output power exceeds that of a threshold; and

means for determining that an undesirable phenomenon of abnormal noise increase is occurring when said count exceeds a predetermined value, thereby to stop generating said secondary sound from said loudspeaker.

23. A noise-reducing apparatus comprising:

detecting means for detecting a sound pressure of noise;

controlling means for determining an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

at least one loudspeaker for generating the secondary sound;

means for sampling with a predetermined sampling period output power of the signal, said output power being proportional to the level of a magnitude of the secondary sound generated from said loudspeaker;

means for counting the number of times the detected output power exceeds that of a threshold; and

means for determining that an undesirable phenomenon of abnormal noise increase is occurring when the ratio of said count to that of a predetermined number of times of sampling is more than a predetermined value, thereby to stop generating said secondary sound from said loudspeaker.

24. A method of using a loudspeaker to reduce noise, comprising the steps of:

detecting a sound pressure of the noise;

determining an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

detecting output power of the signal, said output power being proportional to a magnitude of the secondary sound generated from the loudspeaker;

discriminating whether the detected output power is higher than that of a predetermined threshold; and

determining that an undesirable phenomenon of abnormal noise increase is occurring when the detected output power continues to exceed that of said threshold for at least a predetermined period of time and ceasing generating said secondary sound from said loudspeaker in response thereto.

25. A method of using a loudspeaker to reduce noise, comprising the steps of:

detecting a sound pressure of the noise;

determining an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

detecting output power of the signal, said output power being proportional to a magnitude of the secondary sound generated from said loudspeaker;

discriminating whether the detected output power is higher than that of a predetermined threshold;

adding together time periods for which the detected output power exceeds that of said threshold; and

determining that an undesirable phenomenon of abnormal noise increase is occurring when a value of the time periods added together exceeds a predetermined value and ceasing generating said secondary sound from said loudspeaker in response thereto.

26. A method of using a loudspeaker to reduce noise, comprising the steps of:

detecting sound pressure of the noise;

determining an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

detecting output power of the signal, said output power being proportional to a magnitude of said secondary sound generated from said loudspeaker;

discriminating whether the detected output power is higher than that of a predetermined threshold;

adding together time periods for which the detected output power is higher than that of said threshold; and

determining that an undesirable phenomenon of abnormal noise increase is occurring when a ratio of a value of the time periods added together to a predetermined fixed period of time is more than a predetermined value and ceasing generating said secondary sound from said loudspeaker in response thereto.

27. A method of using a loudspeaker to reduce noise, comprising the steps of:

detecting a sound pressure of the noise;

determining an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

sampling with a predetermined sampling period output power of said signal, said output power being proportional to a magnitude of the secondary sound generated from said loudspeaker;

providing a count of a number of times the sampled output power exceeds that of a threshold; and

determining that an undesirable phenomenon of abnormal noise increase is occurring when said count exceeds a predetermined value and ceasing generating said secondary sound from said loudspeaker in response thereto.

28. A method of using a loudspeaker to reduce noise, comprising the steps of:

detecting a sound pressure of the noise;

determining an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

sampling, with a predetermined sampling period, output power of said signal, said output power being proportional to a magnitude of said secondary sound generated from said loudspeaker;

providing a count of a number of times the sampled output power of the signal exceeds that of a threshold; and

determining that an undesirable phenomenon of abnormal noise increase is occurring when a ratio of said count to that of a predetermined number of times of sampling is more than a predetermined value and ceasing generating said secondary sound from said loudspeaker in response thereto.

29. A noise-reducing apparatus, comprising:

a first detector which detects a sound pressure of noise;

a controller, responsive to said first detector, which determines an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

at least one loudspeaker which generates the secondary sound;

a second detector which detects output power of the signal;

a discriminator, responsive to said second detector which determines whether the detected output power is higher than that of a predetermined threshold; and

a threshold detector which determines that an undesirable phenomenon of abnormal noise increase is occurring when the detected output power of the signal continues to exceed that of said threshold for at least a predetermined period of time and ceases generating said secondary sound from said loudspeaker in response thereto.

30. A noise-reducing apparatus, comprising:

a first detector which detects a sound pressure of noise;

a controller, responsive to said first detector which determines an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

at least one loudspeaker which generates the secondary sound;

a second detector which detects output power of the signal, said output power being proportional to a magnitude of said secondary sound generated from said loudspeaker;

a discriminator, responsive to said second detector which determines whether or not the detected output power is higher than that of a predetermined threshold;

an adder which adds together time periods for which the detected output power exceeds that of said threshold; and

a threshold detector which determines that an undesirable phenomenon of abnormal noise increase is occurring when a value of the time periods added by said adder exceeds a predetermined value and ceases generating said secondary sound from said loudspeaker in response thereto.

31. A noise-reducing apparatus, comprising:

a first detector which detects sound pressure of noise;

a controller, responsive to said first detector, which determines an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

at least one loudspeaker which generates the secondary sound;

a second detector which detects output power of the signal, said output power being proportional to a magnitude of said secondary sound generated from said loudspeaker;

a discriminator, responsive to said second detector, which determines whether or not the detected output power is higher than that of a predetermined threshold;

an adder which adds together time periods for which the detected output power is higher than that of said threshold; and

a threshold detector which determines that an undesirable phenomenon of abnormal noise increase is occurring when a ratio of a value of the time periods added by said adder to a predetermined fixed period of time is more than a predetermined value, and thereby ceases generation of said secondary sound from said loudspeaker.

32. A noise-reducing apparatus, comprising:

a first detector which detects a sound pressure of noise;

a controller, responsive to said first detector, which determines an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

at least one loudspeaker which generates the secondary sound;

a sampler which samples, with a predetermined sampling period, output power of the signal, said output power being proportional to a magnitude of the secondary sound generated from said loudspeaker;

a counter that provides a count of a number of times the detected output power exceeds that of a threshold; and

a threshold detector which determines that an undesirable phenomenon of abnormal noise increase is occurring when said count exceeds a predetermined value and ceases generating said secondary sound from said loudspeaker in response thereto.

33. A noise-reducing apparatus, comprising:

a first detector which detects a sound pressure of noise;

a controller, responsive to said first detector, which determines an amplitude and a phase of a signal to produce secondary sound required for reducing the detected noise;

at least one loudspeaker which generates the secondary sound;

a sampler that samples, with a predetermined sampling period, output power of the signal, said output power being proportional to a magnitude of said secondary sound generated from said loudspeaker;

a counter that provides a count of a number of times the detected output power exceeds that of a threshold; and

a threshold detector which determines that an undesirable phenomenon of abnormal noise increase is occurring when a ratio of said count to that of a predetermined number of times of sampling is greater than a predetermined value and ceases generating said secondary sound from said loudspeaker in response thereto.