Active noise control system for automotive vehicle

• US 5,245,664 A
• Filed: 12/21/1990
• Issued: 09/14/1993
• Est. Priority Date: 12/29/1989
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Kinoshite, Akio, Aoki, Hirofumi
• Primary Examiner(s): Ng, Jin F.
• Assistant Examiner(s): TONG, NINA C
• Application Number:
  US07/629,637
• Time in Patent Office: 998 Days
• Field of Search: 381/71
• US Class Current: 381/71.4
• 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 2210/1282 Automobiles
• CPC Class Codes: G10K 2210/12821 Rolling noise; Wind and body noise
• CPC Class Codes: G10K 2210/3046 Multiple acoustic inputs, multiple acoustic outputs
• CPC Class Codes: G10K 2210/3221 Headrests, seats or the like, for personal ANC systems

Abstract

An active noise control system includes a plurality of vibration pickups for detecting of physical quantities of noise sources, such as vibrations of suspension members of a vehicle, and a plurality of microphones for detecting residual noises transmitted to observing positions. The output signals of the vibration pickups are added up by means of an adder to be input to a controller. The active noise control system also includes a plurality of delay circuits for applying delay times to the respective output signals of the vibration pickups so as to essentially equalize transmitting time of one of the output signals with that of the other output signals. The output signals of the microphones are input to the controller independently of each other. The controller outputs drive signals to a plurality of loudspeakers independent of each other to cause the loudspeakers to produce control sounds so that the control sounds interfere with the noises transmitted from the noise sources to decrease the noises transmitted to the observing positions.

Claims

1. An active noise control system for decreasing noises transmitted to an observing position from a plurality of independent noise sources, said system comprising:

a plurality of noise source detecting means for monitoring physical quantities of individual noise sources to produce first signals indicative of the physical quantities of the noise sources;

signal collecting means for collecting said first signals to produce a second additive signal indicative of the sum of the first signals, said signal collecting means comprising time delay adjusting means for adjusting a time difference between reception of said respective first signals from said noise source detecting means to the signal collecting means in accordance with each respective propagation delay of said first signals at said observing position;

residual noise detecting means for monitoring a residual noise transmitted to the observing position to produce a third signal indicative of the residual noise;

sound source means, arranged at a location neighboring the observing position, for producing a control sound to cause the noise transmitted from the noise sources to interfere with the control sound so as to decrease the noise transmitted to the observing position; and

control means for receiving said second and third signals to produce a fourth signal for deriving the sound source means on the basis of the second and third signals.

2. An active noise control system as set forth in claim 1, wherein said noise source detecting means are arranged at locations proximate individual noise sources.

3. An active noise control system for decreasing noises transmitted to an observing position from a plurality of independent noise sources as set forth in claim 1, wherein said control means includes an adaptive noise cancelling adaptor of a finite impulse response type which receives first signals passed through the signal collecting means weighted with respective weight coefficients, carries out adaptive noise cancelling filtering operation using filter coefficients and outputs the fourth signal.

4. An active noise control system for decreasing noises transmitted to an observing position from a plurality of independent noise sources, said system comprising:

a plurality of noise source detecting means for monitoring physical quantities of individual noise sources to produce first signals indicative of the physical quantities of the noise source;

signal collecting means for collecting said first signals to produce a second additive signal indicative of the sum of the first signals;

residual noise detecting means for monitoring a residual noise transmitted to the observing position, to produce a third signal indicative of the residual noise;

sound source means, arranged at a location neighboring the observing position, for producing a control sound to cause the noises transmitted from the noise sources to interfere with the control sound so as to decrease the noises transmitted to the observing position; and

control means for receiving said second and third signals to produce a fourth signal for driving the sound source means on the basis of the second and third signals.

wherein said system is applied to an automotive vehicle;

wherein said noise source detecting means are mounted on the outer peripheries of tire wheels for detecting air pressures within tires to produce said first signals in accordance with the air pressures within the tires.

5. An active noise control system for decreasing noises transmitted to an observing position from a plurality of independent noise sources, said system comprising:

a plurality of noise source detecting means for monitoring physical quantities of individual noise sources to produce first signals indicative of the physical quantities of the noise source;

signal collecting means for collecting said first signals to produce a second additive signal indicative of the sum of the first signals;

residual noise detecting means for monitoring a residual noise transmitted to the observing position, to produce a third signal indicative of the residual noise;

sound source means, arranged at a location neighboring the observing position, for producing a control sound to cause the noises transmitted from the noise sources to interfere with the control sound so as to decrease the noises transmitted to the observing position; and

control means for receiving said second and third signals to produce a fourth signal for driving the sound source means on the basis of the second and third signals,

wherein said system is applied to an automotive vehicle;

wherein said noise source detecting means are mounted on members fixed to a vehicular body at locations behind door mirrors for detecting pressure fluctuations behind the door mirrors to produce said first signals in accordance with the pressure fluctuations behind the door mirrors.

6. An active noise control system for decreasing noises transmitted to an observing position from a plurality of independent noise sources, said system comprising:

a plurality of noise source detecting means for monitoring physical quantities of individual noise sources to produce first signals indicative of the physical quantities of the noise source;

signal collecting means for collecting said first signals to produce a second additive signal indicative of the sum of the first signals;

residual noise detecting means for monitoring a residual noise transmitted to the observing position, to produce a third signal indicative of the residual noise;

sound source means, arranged at a location neighboring the observing position, for producing a control sound to cause the noises transmitted from the noise sources to interfere with the control sound so as to decrease the noises transmitted to the observing position; and

control means for receiving said second and third signals to produce a fourth signal for driving the sound source means on the basis of the second and third signals,

wherein said system is applied to an automotive vehicle;

wherein said noise source detecting means are mounted on connecting members, one of which connects front-right and front-left suspension members to each other, and the other of which connects rear-right and rear-left suspension members, each of said noise detecting means detecting the sum of vibrations of right and left suspension wheels to produce said first signals in accordance with the sum of the vibrations thereof.

7. An active control system for decreasing noises transmitted to an observing position from a plurality of independent noise sources, said system comprising:

a plurality of noise source detecting means for monitoring physical quantities of individual noise sources to produce first signals indicative of the physical quantities of the noise source;

signal collecting means for collecting said first signals to produce a second signal indicative of the sum of the first signals;

delay circuit means interposed between the noise source detecting means and control means for applying delay times to the respective first signals so as to essentially equalize the time at which the first signals are transmitted to the signal collecting means said delay times being set individually independent from each other for respective sound sources;

residual noise detecting means for monitoring a residual noise transmitted to the observing position, to produce a third signal indicative of the residual noise;

sound source means, arranged at a location neighboring the observing position, for producing a control sound to cause the noises transmitted from the noise sources to interfere with the control sound so as to decrease the noises transmitted to the observing position; and

control means for receiving said second and third signal to produce a fourth signal for driving the sound source means on the basis of the second and third signals.

8. An active noise sound control system for decreasing noises transmitted to an observing position from a plurality of noise sources applicable to a vehicular compartment, the system comprising:

a plurality of noise source detecting means for monitoring physical quantities of individual noise sources of the vehicle to produce first signals indicative of the physical quantities of the noise source;

signal collecting means for collecting said first signals to produce a second additive signal indicative of the sum of the first signals, said signal collecting means having time delay adjusting means for adjusting a time difference between reception of said respective first signals from said noise source detecting means to the signal collecting means with each propagation delay of said first signals at said observing position taken into consideration;

residual noise detecting means for monitoring a residual noise transmitted to the observing position, to produce a third signal indicative of the residual noise;

sound source means, arranged at a location neighboring the observing position, for producing a control sound to cause the noise transmitted from the noise sources to interfere with the control sound so as to decrease the noise transmitted to the observing position; and

control means for receiving said second and third signals to produce a fourth signal for driving the sound source means on the basis of the second and third signals.

9. An active noise control system applied to an automotive vehicle for decreasing noises transmitted to an observing position from a plurality of independent noise sources, said system comprising:

a plurality of noise source detecting means for monitoring physical quantities of individual noise sources to produce first signals indicative of the physical quantities of the noise source;

signal collecting means for collecting said first signals to produce a second additive signal indicative of the sum of the first signals;

residual noise detecting means for monitoring a residual noise transmitted to the observing position, to produce a third signal indicative of the residual noise;

sound source means, arranged at a location neighboring the observing position, for producing a control sound to cause the noises transmitted from the noise sources to interfere with the control sound so as to decrease the noises transmitted to the observing position;

control means for receiving said second third signals to produce a fourth signal for driving the sound source means on the basis of the second and third signals,

wherein said noise source detecting means are mounted on suspension members of the vehicle for detecting vibrations of the suspension members to produce said first signals in accordance with the vibrations thereof.

10. A system for actively cancelling noises derived from a plurality of sound sources having no correlation between each other applicable to a vehicle compartment, comprising:

a) a plurality of sensing means disposed on respective suspension members of the tire wheel portions for detecting and outputting respective road noise signals X₁ to X₄ ;

b) a plurality of loud speakers disposed in door panel inner portions at front right, front left, rear right, and rear left ends of the vehicular compartment so as to face against respective seat positions;

c) a plurality of microphones disposed on head rest positions of respective passenger'"'"'s seats for detecting residual noise sounds and outputting residual noise detection signals e₁ to e₈ ; and

d) a controller having an adder for receiving the road noise signals X₁ to X₄ derived from the respective sensing means and outputting a reference signal X as the added signal for the result of addition, a microprocessor receiving and processing the reference signal X and noise signals e₁ to e₈ from the respective microphones and outputting drive signals Y₁ to Y₄ according to an adaptive filtering process of the controller.

11. A system for actively cancelling noises derived from a plurality of sound sources having no correlation between each other applicable to a vehicular compartment as set forth in claim 10, wherein the controller includes a plurality of delay circuits interposed between the respective sensing means and adder for providing a time difference as a result of subtraction of predetermined delay times Δ

t₁ to Δ

t₄ from a maximum delay time Δ

t max for remaining road noise signals X₁, X₂ and X₄ with one of the road noise signals having the maximum time delay Δ

t max as the reference so that arrival times of controlled sounds from the loud speakers to a receiving point of inner space of the vehicular compartment which corresponds to positions of ear portions of a vehicular driver are coincident with each other.

12. A system for actively cancelling noises derived from a plurality of sound sources having no correlation between each other applicable to a vehicular compartment as set forth in claim 11, wherein said controller further includes an adaptive noise cancelling filter of a Finite Impulse Response type having individual filters according to the number of channels connected to the loud speakers which receive the reference signal X from the adder, carries out the adaptive noise filtering operations on the basis of currently set filter coefficients Wmi (m+1), and outputs the speaker drive signals Y₁ to Y₄.

13. A system for actively cancelling noises derived from a plurality of sound sources having no correlation between each other applicable to a vehicular compartment as set forth in claim 12, wherein said controller includes a digital filter which receives the reference signal X from the adder and produces a filtered reference signal r_1m according to a number of transfer functions between the respective microphones and loud speakers and wherein said adaptive noise cancelling filter is functionally provided with a plurality of filters whose number corresponds to the number of output channels to the respective loud speakers for receiving the reference signal X, executing adaptive signal processing on the basis of filter coefficients set at the time of inputting the reference signal X, and outputting the drive signals Y₁ to Y₄ and the microprocessor functions to receive the filtered reference signal r_1m and residual noise detection signals e₁ to e₈ and to modify the respective filter coefficients of the adaptive noise cancelling filter using a LMS algorithm.

14. A system for actively cancelling noises derived from a plurality of sound sources having no correlation between each other applicable to a vehicular compartment as set forth in claim 13, wherein the reference signal x(n) at a predetermined sampling period n derived from the adder is expressed as follows:

##EQU7## wherein, β

_i denotes a weight coefficient and N_i denotes the predetermined delay times set for the respective delay circuits.

15. A system for actively cancelling noises derived from a plurality of sound sources having no correlation between each other applicable to a vehicular compartment as set forth in claim 14, wherein said digital filter calculates the filtered reference signal r_1m correspondingly to the filter coefficients C_1m which correspond to transfer functions between the microphones and speakers as follows:

##EQU8## wherein, C_1mj denotes the filter coefficient corresponding to j number (j=0, 1, 2, . . , I_c -1) of the transfer function (Finite Impulse Response function) between an m number of the loud speakers and an 1 number of microphones, and wherein said digital filter outputs the filtered reference signal r_1m as the result of calculation to the microprocessor.

16. A system for actively cancelling noises derived from a plurality of sound sources having no correlation between each other applicable to a vehicular compartment as set forth in claim 15, wherein said microprocessor carries out an updating calculation of the filter coefficients on the basis of the following equation:

##EQU9## wherein, W_mi denotes the coefficient of the i number of the filter coefficients of the adaptive filter to derive the m number of the loud speakers, α

denotes a converging coefficient of the adaptive filter, r₁ denotes a weight coefficient e₁ denotes the residual noise detection signal output from the 1 number of the microphones.

17. A system for actively cancelling noises derived from a plurality of sound sources having no correlation between each other applicable to a vehicular compartment as set forth in claim 16, wherein said adaptive filter derives the output values y_m of the drive signals according to a vector calculation of the reference signal X and filter coefficients W_mi as follows:

space="preserve" listing-type="equation">Y.sub.m =Σ

W.sub.mi ·

x(n-j-i).