JPH06161466A - Sound eliminating device - Google Patents

Abstract

PURPOSE:To provide the sound eliminating device which is arranged closely to the ear during a normal travel to attenuate a travel noise auditorily effectively, and stored in a headrest and not an obstacle at riding-ON/OFF time and during a backward travel. CONSTITUTION:This sound eliminating device consists of an acceleration sensor 8 which detects a noise, adaptive filters 12a and 12b which perform adaptive control over a detected noise signal, speakers 2a and 2b which reproduce the outputs of the adaptive filters 12a and 12b, microphones 3a and 3b which detect a noise at a control point, FIR filters 13a and 13d which process the noise signal from the acceleration sensor 8, LMS computing elements 14a-14d which calculate and update the coefficients of the adaptive filters 12a and 12b from the outputs of the filters and the outputs of the microphones 3a and 3b, and coefficient adders 15a-15b; and the speakers 2a and 2b and microphones 3a and 3b are constituted in one body in a speaker box, which is movable to and away from the headrest.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffler using active noise control in a noisy environment.

[0002]

2. Description of the Related Art In recent years, an active noise control method has been proposed in which a control sound is output from a speaker by using a digital signal processing technique to mute environmental noise at a listening position.

A conventional silencer will be described below with reference to the drawings. (FIG. 8) and (FIG. 9) are block diagrams of a conventional silencer. In FIGS. 8 and 9, 2a and 2b are speakers for car audio mounted near doors, rear trays or dashboards, and 3a and 3b are microphones mounted near the headrest 5, for example, on the ceiling. Headrest attached to the seat, 6 is a seat body, 8 is an acceleration sensor, 9 is an engine, 10 is a control unit, 11 is a passenger compartment, 1
2a and 12b are adaptive filters, and 13a to 13d.
Is an FIR filter, 14a to 14d are LMS calculators, 1
5a to 15b are coefficient adders.

The operation of the muffler having the above structure will be described below. The noise signal detected by the acceleration sensor 8 attached to the engine 8 is input to the adaptive filter 12a in the control unit 10. The signal adaptively controlled here is the speaker 2
Reproduced by a. The reproduced sound and the noise from the noise source interfere with each other, and the interference sound is detected by the microphones 3a and 3b. On the other hand, the noise signal from the acceleration sensor 8 is FI
Signal processing is performed by the R filters 13a and 13b. Here, the transfer function from the speaker 2a to the microphone 3a is identified in advance in the FIR filter 13a.
The transfer function from the speaker 2a to the microphone 3b is previously identified in the R filter 13b. And FIR
The output of the filter 13a and the output of the microphone 3a are respectively input to the LMS calculator 14a, and coefficients are obtained so that the signal from the microphone 3a is minimized.
The output of b and the output of the microphone 3b are respectively input to the LMS calculator 14b, the coefficients are obtained so that the signal from the microphone 3b is minimized, and the coefficients are added by the coefficient adder 15a to obtain the coefficient of the adaptive filter 12a. To update.

[0005] Now, W ₁ the coefficients of the adaptive filter 12a, each r ₁₁ the output of the FIR filter 13A-13B, r _12, the coefficient update equation of the adaptive filter 12a and the output of the microphone 3a~3b and e _1, e ₂ Is

[0006]

[Equation 1]

It is expressed as Similarly, the coefficient update formula of the adaptive filter 12b is

[0008]

[Equation 2]

It is represented by Therefore, the adaptive filters 12a and 12b adaptively control the input signals so as to reduce the detection signals e1 and e2 at the microphones 3a and 3b according to (Equation 1) and (Equation 2). As a result, noise generated from the engine 9 to which the acceleration sensor 8 is attached is attenuated by the microphones 3a to 3b.

This control algorithm is called Multiple Error F
iltered-x LMS (SJ Elliott, IM Stothers and P.
A. Nelson, "A multple error LMS algorithm and its
application to the active control of sound and vib
ration. "IEEE Trans.Acoust. Speech Signal Process.
ASSP-35, pp1423-1434 (1987))
Say.

Next, consider the case of controlling a plurality of noise sources such as road noise. (FIG. 10) shows a block diagram of the silencer when two noise sources are present. (Figure 10)
2a and 2b are car audio speakers mounted near doors, rear trays or dashboards, 3a and 3b are microphones mounted near the headrest 5, for example, on the ceiling, and 8a and 8b are mounted on suspensions near the tires. Acceleration sensor, 12a-12
d is an adaptive filter, 13a to 13h are FIR filters, 14a to 14h are LMS calculators, and 15a to 15
d is a coefficient adder, and 16a and 16b are signal adders.

As can be seen from FIG. 10, the algorithm shown in FIG. 9 is applied to each noise source, and the noises generated from the two noise sources are combined by the signal adders 16a and 16b. It can be attenuated at 3b.

[0013]

[Problems to be Solved by the Invention] However (FIG. 8)
As described above, when a door speaker that is often found in general car audio and a speaker near the front tray, the rear tray, or the dashboard are used as the control speakers 2a and 2b, the speakers 2a and 2b and the microphones 3a and 3b are used.
Distance (C11, C12, C21, C22 in (Fig. 9))
Therefore, the processing speed of the control unit 10 must be very high in order to control the random sound such as the transient sound and road noise of the engine 8, and if the processing speed cannot catch up with the noise transmission speed. In this case, there is a problem that it cannot be controlled, or that the volume of sound cannot be sufficiently reduced.

Further, when the microphones 3a and 3b are installed on the ceiling or the like, the microphones 3a and 3b are located far from the ears of the occupants, so that there is a problem in that a sufficient sound deadening effect cannot be obtained.

The present invention solves the above-mentioned problems, and the engine muffled noise and road noise during normal running are obtained without disturbing the user when getting on and off the vehicle and without obstructing the rear view when moving backward. A muffling device that can sufficiently attenuate random noise such as noise or wind noise at the ears of passengers.

[0016]

In order to achieve this object, a silencer of the present invention comprises a noise detector for detecting noise from a noise source, an adaptive filter for adaptively controlling the detected noise signal, and a noise detector for the noise detector. A speaker that is movable with respect to the headrest of the in-vehicle seat that reproduces the output, and a speaker that is integrated with the speaker by being installed immediately before the speaker that detects the reproduced sound of the speaker and the noise from the noise source and uses it as the error signal of the adaptive filter And an error detector.

[0017]

With this configuration, the speaker and the error detector are arranged near the ears of the occupant during normal traveling, so that audible traveling noise can be sufficiently attenuated.

Further, since the speaker and the error detector are housed in the headrest when getting in and out of the vehicle or when moving backward, there is no obstruction to getting in or out of the vehicle or obstruction of the rear view.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

(FIG. 1) to (FIG. 4) show the arrangement of the control speaker and the error detecting microphone of the silencer in one embodiment of the present invention. (FIG. 1) is a top view, (FIG. 2) is a front view, and (FIG. 3) and (FIG. 4) are left side views. In (FIG. 1) to (FIG. 4), 1a,
1b is a speaker box in which a control speaker and an error detection microphone are attached, 2a and 2b are speakers, 3a and 3
Reference numeral b is a microphone, 4 is a movable support device having a structure that supports and can move the speaker boxes 1a and 1b, 5 is a headrest, 6 is a seat body, and 7 is a passenger sitting on the seat 6.

By the way, the speakers 2a and 2b and the microphone 3
Needless to say, a and 3b are connected to the control unit 10 as shown in (FIG. 9) and (FIG. 10). The operation of the muffling device configured as described above will be described below.

First, during normal running, the speaker boxes 1a and 1b are arranged near the ears of the occupant 7 while moving forward as shown in FIGS. 1 and 3. As can be seen from these figures, the speakers 2a, 2b and the microphones 3a, 3
b and the ears of the passenger 7 are very close to each other.
Therefore, the coefficients (C11, C12, C21, C) of the FIR filters 13a to 13h described in (FIG. 9) and (FIG. 10) are used.
22), the delay time becomes small. Therefore, the time required for the sounds reproduced by the speakers 2a to 2b to reach the ears of the passengers 7 is sufficiently shorter than the time required for the engine noise and road noise due to vibrations from the road surface to reach the ears of the passenger 7. A sufficient margin can be obtained in the processing time, and the running noise can be reliably damped by this. Further, since the control point is near the ears of the occupant 7, the sound deadening effect obtained by the microphones 3a and 3b is almost the same as the auditory effect, so that the effect can be seen very well. Furthermore, since the number of taps of the FIR filters 13a to 13h can be reduced, the size can be reduced. Further, as can be seen from (FIG. 2), the microphones 3a and 3b and the speakers 2a and 2b are close to each other, which is very advantageous for the low-frequency reproduction capability of the speakers 2a and 2b, and the speakers 2a and 2b can be downsized. .

Next, when the vehicle is going backwards by entering the garage, etc., or when the vehicle is not in normal driving such as getting on and off at the parking lot (FIG. 4)
The speaker boxes 1a and 1b as shown in FIG.
To the side of. As a result, it is possible to prevent getting in and out of the vehicle and deterioration of the backward visibility.

As described above, the speaker boxes 1a and 1b
Is attached to the movable support device 4 so as to be movable back and forth, and its structure is similar to a so-called radio rod antenna.

Further (FIG. 5) is a side view of the seat 6 and the headrest 5. The headrest 5 is movable from the position shown by the wavy line to the position shown by the solid line, and the headrest 5 of the passenger 7 is Adjustable to contact. As a result, the positions of the speaker boxes 1a and 1b can be arranged at the ear of each person for everyone. Therefore, it is possible to prevent the auditory effect from greatly different for each individual.

The movement of the peaker boxes 1a, 1b and the headrest 5 may be performed manually, but may be performed electrically using a motor or the like. At that time, for example, when the speaker boxes 1a and 1b are moved, whether the microprocessor confirms that all the doors are properly closed when the engine is started, and further confirms that the transmission is in the forward movement (low gear or D range). Alternatively, when it is confirmed that the wheels are moving forward by the direction of rotation of the propeller shaft, axle shaft, etc., it is determined that the vehicle is in a normal traveling state, and the speaker box 1a,
The microprocessor controls so that 1b moves forward from the headrest 5 (FIG. 1). Next, when the vehicle is going backwards by putting it in a garage, etc., make sure that the transmission is going backwards or if the wheels are rotating in the backward direction (see FIG. 4). Is stored in the headrest 5. When the vehicle is stopped with the engine running, the microprocessor stores the speaker boxes 1a and 1b in the headrest 5 when the door is opened.
When the door closes again and moves forward, the speaker box 1a,
1b is brought into the state of (FIG. 1). Further, when the engine is stopped and the vehicle is parked, the microprocessor controls that the speaker boxes 1a and 1b are housed in the headrest 5 after confirming that the engine is stopped.

Regarding the movement of the headrest 5, for example, a pressure sensor is installed at a place where the head of the occupant will hit, and the output of the pressure sensor allows the microprocessor to judge whether or not the headrest 5 is in contact with the head. Move the headrest 5 to the optimum position.

Next, another embodiment of the present invention will be described. (FIG. 6) shows a state where the speaker boxes 1a, 1b move from the headrest 5 and noise control is possible during normal running, and (FIG. 7) shows the speaker boxes 1a, 1b.
It shows that b is stored in the headrest 5. As described above, the speaker boxes 1a and 1b may be housed in the headrest 5, and the same effect as above can be obtained.

[0029]

According to the present invention, since the speaker and the error detector can be integrally arranged at the ears of the occupant at the time of normal traveling, the traveling noise can be effectively attenuated in hearing and the speaker Can be small. Furthermore, by storing the speaker and the error detector in the headrest when getting in and out of the vehicle or moving backward, it is possible to realize an excellent muffling device that does not interfere with getting in and out of the vehicle or obstruct the rear view.

[Brief description of drawings]

FIG. 1 is a diagram showing a positional relationship between a control speaker and an error detection microphone of a silencer according to an embodiment of the present invention.

FIG. 2 is a diagram showing a positional relationship between a control speaker and an error detection microphone of the silencer according to the embodiment of the present invention.

FIG. 3 is a diagram showing a positional relationship between a control speaker and an error detection microphone of a silencer according to an embodiment of the present invention.

FIG. 4 is a diagram showing a positional relationship between a control speaker and an error detection microphone of the silencer according to an embodiment of the present invention.

FIG. 5 is a view showing a seat and a headrest.

FIG. 6 is a diagram showing a control speaker of a silencer according to another embodiment of the present invention.

FIG. 7 is a diagram showing a control speaker of a silencer according to another embodiment of the present invention.

FIG. 8 is a diagram showing a conventional silencer.

FIG. 9 is a block diagram showing an algorithm of a conventional silencer.

FIG. 10 is a block diagram showing an algorithm of a conventional silencer.

[Explanation of symbols]

 1a, 1b Speaker box 2a, 2b Speaker 3a, 3b Microphone 4 Movable support device 5 Headrest 6 Seat 7 Passenger 8 Accelerometer 9 Engine 10 Control unit 11 Cab 12a-12d Adaptive filter 13a-13h FIR filter 14a-14h LMS Arithmetic unit 15a to 15d Coefficient adder 16a, 16b Signal adder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Tamura 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A noise detector for detecting noise from a noise source, an adaptive filter for adaptively controlling a noise signal detected by the noise detector, and an output of the adaptive filter for attenuating noise of an automobile. A speaker installed on the headrest of the in-vehicle seat that reproduces the noise, and an error detector installed immediately in front of the speaker that detects the reproduced sound of the speaker and the noise from the noise source and uses it as the error signal of the adaptive filter. A silencer, wherein the error detector is integrated with the speaker, and the speaker and the error detector are movable with respect to a headrest. 2. The silencer according to claim 1, wherein the speaker and the error detector are housed in the headrest when the vehicle moves backward, when the vehicle gets on and off, or when the engine is stopped. 3. The headrest has a pressure sensor at a portion with which the head of a person sitting on the seat comes into contact, and judges whether the head is in contact with the output signal of the pressure sensor. The muffler according to claim 1, wherein the muffler moves forward until it comes into contact.