JPH05333873A - Noise reducing device - Google Patents

Abstract

PURPOSE:To provide the noise reducing device which has good sound insulating performance and is small in size and comfortably put on. CONSTITUTION:A mount member 30 mounted in the concha is fitted with a microphone 37 for reference input which absorbs a noise 40, a sound radiating means 33 which radiates a canceling sound directly to the auditory meatus, and a microphone 34 for residue detection which gathers a noise residue nearby the auditory meatus. A canceling sound generating means 44 generates the canceling sound for canceling the noise gathered by the microphone 37 for reference input from the noise. The canceling sound generating means 44 is so adjusted as to minimize the residue signal gathered by the microphone 34 for residue detection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small noise reduction device that acoustically reduces noise.

[0002]

2. Description of the Related Art Conventionally, a noise signal having a phase opposite to that of a noise source and an amplitude equal to that of the noise signal is formed, and the voice signal is emitted by a speaker to cancel the noise from the noise source to reduce the noise. The system is known.

FIG. 12 is a diagram showing an outline of an example of this type of noise reduction device. That is, in FIG.
Is a reference input microphone for collecting noise from the noise source 10. The noise voice signal obtained from the reference input microphone is supplied to the cancellation sound forming circuit 12, and a voice signal having an opposite phase and an equal amplitude is formed with respect to the noise generated from the noise source 10. The canceling sound from the canceling sound forming circuit 12 is supplied to the speaker 13 and is emitted to reduce noise.

Reference numeral 15 is a residual detection microphone for collecting noise residuals in the sound field 14 near the ear.
The residual obtained from this residual detection microphone is fed back to the cancellation sound forming circuit 12, and the cancellation sound forming circuit 12 reforms the cancellation sound so that the residual becomes zero.

By the way, in the noise reduction system as shown in FIG. 11, the speaker 13 as an output device is used.
Is installed in a room or hall, and noise is spatially reduced for the entire room or hall. Ideally, the reference input microphone 11 is arranged near the noise source 10, while the residual detection microphone 15 is ideally arranged on the human ear, more precisely, on the eardrum side.

Further, conventionally, a system in which a speaker and a residual detection microphone 15 are installed around a chair is known.

[0007]

However, in this noise reduction system, the positions of the speaker and the microphone are
Since it is installed in a considerably distant position and is large in size, it is difficult to move and has a drawback of taking up a large space. Further, since the residual detection microphone is installed at a physically fixed predetermined position and the noise is reduced only in the surrounding area, the area where the noise is reduced is limited. Therefore, there is a problem that the noise reduction effect is reduced due to the movement of the human head or body.

Therefore, as shown in FIG. 13, as a small noise reduction device, a cancellation sound is emitted from a headphone driver, and a reference input microphone and a residual detection microphone are incorporated in the headphone. Is being considered.

That is, FIG. 13 shows a headphone for one ear, and 20 shows the headphone as a whole. A headphone driver 21 is provided inside the headphones 20. In addition, an ear pad 22 is provided on a portion of the headphone 20 that is in contact with a person. When the headphone 20 is worn by a person, the part that is open to the outside, that is, the direction in which sound waves are emitted from the headphone driver 21, is
A reference microphone 23 is attached to the back side portion on the opposite side. The reference input microphone 23 is a microphone for picking up noise generated around the ears, and its diaphragm surface is arranged toward the outside of the headphones.

Further, a cover 24 is provided on the front surface of the headphone driver 21 in the sound emission direction, and a microphone 25 for residual detection is provided on the cover 24, and its diaphragm surface faces the headphone driver 21 side. Are arranged in this way. In this case, two microphones 23 and 25 are arranged across the headphone driver 21 to provide a difference in paths of about the time required for processing for minimizing the residual difference in the cancellation sound forming circuit 12.

According to this noise reduction device using the headphone system, the headphone itself is smaller than the above-mentioned system, and in addition, the sound insulation effect of the headphones itself is a great advantage.

However, in this headphone type noise reduction device, the pressure feeling around the ears by the ear pads 22 becomes a problem, and there is a drawback that wearing for a long time causes a great feeling of fatigue to humans. Moreover, even though it is compact, further miniaturization is desired for portability.

In view of the above points, an object of the present invention is to provide a noise reduction device which is more compact, has a good feeling of wearing, and can withstand wearing for a long time.

[0014]

In order to solve the above-mentioned problems, the noise reducing device according to the present invention has a mounting member 3 to be mounted in the auricle when the reference numerals of the embodiments described later correspond to each other.
0 (or 50), and when the mounting member is mounted in the auricle, the mounting member is mounted on a portion exposed to the outside, and the reference input microphone 37 (or 54) for collecting noise. ), And a canceling sound forming means 44 for forming a canceling sound for canceling the noise from the noise picked up by the reference input microphone, and the canceling sound directly attached to the ear canal, which is attached to the mounting member. Sound emitting means 33 (or 55) for emitting a sound,
A residual detection microphone 34 (or 56) attached to the mounting member, for collecting a noise residual in the vicinity of the ear canal whose noise is reduced by the cancellation sound emitted from the sound emitting means. The residual signal picked up by the residual detection microphone is supplied to the canceling sound forming means 44, and the canceling sound forming means 44 is adjusted to minimize the residual difference.

[0015]

In the canceling sound forming means 44, a noise canceling sound is formed from the audio signal from the reference input microphone. The noise canceling sound is emitted to the ear canal by the sound emitting means. The residual detection microphone picks up the noise residual near the ear canal. The collected residual signal is supplied to the canceling sound forming means, and the canceling sound forming means is adjusted so that the residual difference is minimized.

Since the reference input microphone, the sound emitting means, and the residual detection microphone are mounted on the mounting member mounted in the auricle, a noise reduction device having a small size and a comfortable fit can be obtained.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of a noise reducing device according to the present invention will be described below with reference to the drawings.

In the example of the noise reducing device of the present invention described below, the mounting member is a so-called earphone type.
There are roughly two types of earphone shapes, one of which is a type in which a disk-shaped earphone body is simply attached to the ear canal entrance in the ear canal (hereinafter referred to as type A).
The other type is a type having an insertion portion into the ear canal (hereinafter referred to as type B).

First, an embodiment of the earphone type A will be described with reference to FIG. The basic configuration of the present invention is to attach all of the earphone driver, the reference input microphone, and the residual detection microphone to the earphone, but the configuration of this type A is
A small residual detection microphone is provided adjacent to the earphone driver, and a small reference input microphone is arranged toward the outside of the earphone.

That is, in FIG. 1, reference numeral 30 generally indicates a disc-shaped earphone. This earphone 30
The whole is housed in the concave portion of the ear canal entrance portion in the auricle and attached to the ear.

As shown in FIG. 1A, the one surface 31 side of the earphone 30 is a sound emitting surface, and the earphone driver 33 is attached so that the sound emitting direction faces the surface 31 side. When the earphone 30 is mounted in the auricle, the sound wave emitted from the earphone driver 33 is directly emitted from the surface 31 to the ear canal entrance. Further, in this example, the residual detection microphone 34 is attached to the central portion of the surface 31 to detect the noise residual in the auditory canal entrance space where noise is canceled by the sound wave emitted from the earphone driver 33. Is configured as follows.

The surface 32 of the earphone 30 opposite to the sound emitting surface 31 is exposed to the outside when the earphone 30 is mounted in the auricle. An earphone cord connecting portion 35 is provided on the surface 32 side exposed to the outside, and an earphone cord 36 is led out from the connecting portion 35. Further, a reference input microphone 37 is attached to the surface 32 side such that its diaphragm is directed to the outside and noise from the outside is picked up.

In this type A example, the mounting positions of the earphone driver 33 and the residual detection microphone 34 are not limited to those shown in FIG. 1A.

2 and 3 show another example of the mounting positions of the earphone driver 33 and the residual detection microphone 34. In both cases, the sound emitting surface 31 side of the earphone 30 is spatially divided. Split the earphone driver 33
And the mounting position of the residual detection microphone 34 is secured. That is, in the example of FIG. 2, the surface side facing the auditory canal entrance is divided into two, one semicircular space is the sound emission space by the earphone driver 33, and the other semicircular space is the residual detection microphone. This is the position for attaching 34.

In the example of FIG. 3, the size of the earphone driver 33 having a circular sound emitting surface is made smaller than the circular portion of the surface 31, and the earphone driver 33 is also provided.
Is placed at a position where its center is eccentric from the center of the circular portion of the surface 31. And this earphone driver 3
The residual detection microphone 34 is mounted in the space of the gap generated when 3 is small.

In the circuit configuration example of the noise reduction device according to the present invention, an adaptive processing circuit is used for noise reduction. Before describing this embodiment, FIG.
The adaptive noise reduction circuit will be described with reference to FIG.
In FIG. 4, 1 is a main input terminal, 2 is a reference input terminal, and the signal input through the main input terminal 1 is supplied to the combining circuit 4 through the delay circuit 3. In addition, the signal input through the reference input terminal 2 is an adaptive filter circuit 5
Is supplied to the synthesizing circuit 4 via. The output of the synthesizing circuit 4 is fed back to the adaptive filter circuit 5 and is also led to the output terminal 6.

In this noise reduction apparatus, the main input terminal 1 is supplied with the desired signal s and a noise n0 uncorrelated with the desired signal s. On the other hand, noise n1 is input to the reference input terminal 2. Noise n1 of this reference input
Is uncorrelated with the desired signal, but is correlated with noise n0.

The adaptive filter circuit 5 has a reference input noise n1.
Is filtered to output a signal y that approximates noise n0. Then, the synthesis circuit 4 performs a process of subtracting the output signal of the adaptive filter circuit 5 from the output signal of the delay circuit 3. The delay circuit 3 takes the processing time in the adaptive filter circuit 5 into consideration.

The adaptive algorithm in the adaptive filter circuit 5 works so as to minimize the subtraction output (residual output) e which is the output of the synthesis circuit 4. That is, now s, n
Assuming that 0, n1 and y are statistically stationary and the average value is 0, the residual output e is e = s + n0-y. The expected value of the square of this is that s is n0,
Also, because it is y ^{uncorrelated, E [e 2] = E} [s 2] + E [(n0 -y) 2] + 2E [s (n0 -y)] = E [s 2] + E [(n0 - y) ² ]. Assuming that the adaptive filter circuit 5 converges,
The adaptive filter circuit 5 is adjusted so that E [e ² ] is minimized. At this time, since E [s ² ] is not affected, Emin [e ² ] = E [s ² ] + Emin [(n 0 -y) ² ]. That, E E by [e ^2] is minimized [(n0 -y) ^2] is minimized, the output y of the adaptive filter circuit 5 will estimate the noise n0. And
The expected value of the output from the combining circuit 4 is only the desired signal s. That is, adjusting the adaptive filter circuit 5 to minimize the total output power is equivalent to the subtraction output e becoming the least-squares estimated value of the desired speech signal s.

The adaptive filter circuit 5 can be realized by either an analog signal processing circuit or a digital signal processing circuit. FIG. 5 shows an example in which the adaptive filter circuit 5 is realized by using a digital filter. This example uses the so-called LMS (Least Mean Square) method as an adaptive algorithm.

As shown in FIG. 5, an FIR filter type adaptive linear combiner 300 is used in this example. this is,
A plurality of delay circuits DL1, DL2, ... DLm (m is a positive integer) each having a delay time Z ⁻¹ of a unit sampling time, input noise n1 and each delay circuit DL1, DL
2, ... DLm is provided with weighting circuits MX0, MX1, MX2, ... MXm for multiplying the output signal of DLm by a weighting coefficient, and an adder circuit 310 for adding the outputs of the weighting circuits MX0 to MXm. The output of the adder circuit 310 is y.

The weighting coefficients supplied to the weighting circuits MX0 to MXm are formed on the basis of the residual signal e from the synthesizing circuit 4 in the LMS arithmetic circuit 320 including, for example, a microcomputer. The algorithm executed by the LMS arithmetic circuit 320 is as follows.

Now, the input vector X _k at time k is
As shown in FIG. 5, X _k = [x _0k x _1k x _2k ... x _mk ] ^T , the output is y _k , and the weighting coefficient is w _jk (j = 0,1,2, ... m). Then, the relationship of input and output is as shown in the following Equation 1.

[0034]

[Equation 1] Becomes

Then, the weight vector W _{k at} time _k
Is defined as W _k = [w _0k w _1k w _2k ... w _mk ] ^T , the input / output relationship is given by y _k = X _k ^T · W _k . Here, if the desired response is d _k , the residual e _k is expressed as follows. e _k = d _k −y _k = d _k −X _k ^T · W _{k In the} LMS method, the weight vector is updated sequentially by the formula W _{k + 1} = W _k +2 μ · e _k · X _k . Here, μ is a gain factor (step gain) that determines the speed and stability of adaptation.

In the noise reduction device which is the object of the present invention,
The synthesizer circuit 4 serves as a sound synthesizer. That is, the adaptive filter circuit 5 forms a noise canceling audio signal -y having a phase opposite to that of the noise and an equal amplitude, and supplies this to the earphone driver 33 to acoustically add to the noise which is the main sound to reduce the noise. The configuration. The residual e in this case is picked up by the residual detection microphone 34.

FIG. 6 is a circuit configuration diagram of an embodiment of the noise reduction device according to the present invention. In this example, the adaptive filter circuit using the digital filter as described above is used. The noise source 40 is the main input.
Only thinking. The noise from this noise source 40 is propagated to the ear 41 as shown in the figure.

At this time, the earphone 3 attached to the ear
The reference input microphone 37 attached to the outer surface 32 of 0 simultaneously picks up noise input to the ear. Sound is picked up by the reference input microphone 37,
The signal obtained by being converted into an electric signal is supplied to the A / D converter 43 via the amplifier 42, converted into a digital signal, and supplied to the adaptive filter circuit 44. Then, the output signal of the adaptive filter circuit 44 is returned to the analog audio signal by the D / A converter 45, and the amplifier 4
It is supplied to the earphone driver 33 via 6. Then, the earphone driver 33 emits the noise canceling sound to the ear canal entrance, and acoustically synthesizes it with the noise sound wave from the noise source 40. At the ear canal entrance of the ear 41, the noise from the noise source 40 is generated. Will be reduced.

Then, the noise residual at the entrance of the ear canal is picked up by the residual detecting microphone 34 attached to the earphone 30 adjacent to the earphone driver 33. The residual error of the ear canal entrance of the ear 12 collected by the residual detection microphone 41 is supplied to the adaptive filter circuit 44 via the amplifier 47. The adaptive filter circuit 44 adjusts its output signal so that the residual is minimized. Thus, the noise is adaptively reduced so that the noise at the ear canal entrance of the ear 12 is minimized.

In this example, the parts from amplifier 42 to amplifier 47 enclosed by dotted lines in the drawing can be carried separately from the earphone 30 and can be connected to the earphone 30 by a cord. In that case, a battery as a power source can be provided on the portable device side. Of course, the parts from the amplifier 42 to the amplifier 47 may be integrated with the earphone 30.

Next, an example of the present invention in the case of earphone type B will be described. Also in this example, the circuit configuration is as shown in FIG.
The same as the example above. For Type B earphones,
Since there is a portion to be inserted into the ear canal, the reference input microphone and the residual detection microphone are attached using this insertion portion. In the case of this type B example,
Compared with the former case, the internal space at the time of mounting is characterized as a small air chamber that is almost closed and a proper volume can be obtained with a small amplitude.

FIG. 7, FIG. 8, FIG. 9, FIG. 10 and FIG.
Examples of this type B are shown in FIG.

In FIGS. 7 to 11, reference numeral 50 represents the type B earphone as a whole. This earphone 5
As shown in the drawing, reference numeral 0 indicates an ear canal insert portion 51 having a hollow shape 52 and a cylindrical shape, and the ear canal insert portion 5
1, and a large diameter portion 53 having a diameter larger than that of the insertion portion 51. The large diameter portion 53 is exposed to the outside when the earphone 50 is attached to the ear. In any of the embodiments, the reference input microphone 54 is attached to the back surface portion of the large diameter portion 53 exposed to the outside so that ambient noise can be detected.

In the example of FIG. 7, the earphone driver 55 is provided at the bottom of the hollow portion 52 of the insertion part 51 in the ear canal. In addition, the residual detection microphone 56
Is also provided at the bottom of the hollow portion 52 in proximity to the earphone driver 55 so that the noise residual in the hollow portion 52 where the sound is reproduced by the earphone driver 55 can be detected.

In the case of the example of FIG. 7, the ear canal insertion portion 5
1 is present and the residual detection microphone 56 is provided in the hollow portion 52 thereof, it is possible to prevent the residual detection microphone 56 from picking up a frictional sound generated by directly touching the skin. it can.

In the example of FIG. 8, the earphone driver 5
5 is provided on the side surface of the hollow portion 52 of the insertion portion 51 in the ear canal at an intermediate portion thereof. On the other hand, the residual detection microphone 56 is provided at the bottom of the hollow portion 52.

In the case of the example of FIG. 8, the same effect as that of the example of FIG. 7 can be obtained, and the earphone driver 55 is used.
7 is larger than that in the example of FIG. 7, the spatial path (voice propagation path) between the two can be lengthened, and the processing time in the adaptive filter circuit 44 is lengthened. It is possible.

The example of FIG. 9 is an example in which the positions of the earphone driver 55 and the residual detection microphone 56 are opposite to those of the example of FIG. 8, and the earphone driver 55 causes the earphone driver 55 to have a bottom portion of the hollow portion 52 of the insertion portion 51. On the other hand, the residual detection microphone 56 is provided in the middle insertion portion of the hollow portion 52.

The examples of FIGS. 8 and 9 are earphones 50.
The noise that has entered from outside and the audio signal generated by the earphone driver 55 are added and propagate to the eardrum in the acoustically canceled state, and the process can be detected by the residual detection microphone 56. ..

In the example of FIG. 10, an earphone driver 55,
Both of the residual detection microphones 56 are examples in which they are attached to the side wall portion of the middle portion of the hollow portion 52 of the ear canal insertion portion 51. In this example, the path between the two can be secured for a relatively long time, and at the same time, the state in which the system output and the noise signal cancel each other can be detected by the residual detection microphone 56, which propagates to the eardrum. It will be like this.

In the example of FIG. 11, an earphone driver 55,
The residual detection microphone 56 has the same arrangement as that of the example of FIG. 7 arranged at the bottom of the hollow portion 52 of the insertion portion 51 into the ear canal. This is an example in which a partition 57 is provided to make the propagation path of the sound wave with the difference detection microphone 56 longer. By doing so, the path from the earphone driver 55 to the residual detection microphone 56 becomes long, and thus the processing time in the adaptive filter circuit 44 can be made relatively long. Therefore, the adaptive filter circuit 4
4 has an advantage that high speed processing is not required.

It should be noted that securing a long path as in the example of FIG. 11 does not cause a problem in a system capable of high-speed processing, and therefore the optimum arrangement is selected in consideration of the entire system. ..

[0053]

As described above, according to the present invention, the reference input microphone and the residual detection microphone are provided in the earphone of the type to be mounted at the entrance of the ear canal or the type to be mounted in the ear canal. I did so,
A very small noise reduction device can be realized.

According to such a small and compact noise reduction device, there is an effect that the sound insulation is improved, and there is no feeling of pressure unlike the above-mentioned headphone type, and it can endure long-time use. In addition, it is very small and lightweight, which is convenient for carrying.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a mounting member of a noise reduction device according to the present invention.

FIG. 2 is a diagram showing another example of a mounting member of the noise reduction device according to the present invention.

FIG. 3 is a diagram showing another example of a mounting member of the noise reduction device according to the present invention.

FIG. 4 is a diagram showing an outline of an adaptive noise reduction system.

FIG. 5 is a diagram showing an example of an adaptive filter circuit.

FIG. 6 is a diagram showing an example of a circuit configuration of a noise reduction device of the present invention.

FIG. 7 is a diagram showing another example of a mounting member of the noise reduction device according to the present invention.

FIG. 8 is a diagram showing another example of a mounting member of the noise reduction device according to the present invention.

FIG. 9 is a diagram showing another example of a mounting member of the noise reduction device according to the present invention.

FIG. 10 is a diagram showing another example of a mounting member of the noise reduction device according to the present invention.

FIG. 11 is a diagram showing another example of a mounting member of the noise reduction device according to the present invention.

FIG. 12 is a diagram showing an outline of a system for acoustically reducing noise.

FIG. 13 is a diagram showing an example of a main part of a previously proposed noise reduction device.

[Explanation of symbols]

 30,50 Earphone 33,55 Earphone driver 34,56 Residual detection microphone 37,54 Reference input microphone 44 Adaptive filter circuit

Claims (4)

[Claims] 1. A mounting member to be mounted in the auricle, and when the mounting member is mounted in the auricle, the mounting member is mounted to a portion exposed to the outside to collect noise. Of the reference input microphone, and a canceling sound forming means for forming a canceling sound for canceling this noise from the noise picked up by the reference input microphone, and the canceling sound forming means attached to the mounting member and directly attached to the ear canal. A sound emitting means for emitting the canceling sound, and a noise residual in the vicinity of the ear canal, which is attached to the mounting member and is noise reduced by the canceling sound emitted from the sound emitting means. And a residual signal picked up by the residual detection microphone is supplied to the cancellation sound forming means, and the cancellation sound forming means minimizes the residual error. Noise reduction device adapted to be urchin adjusted. 2. The noise reduction device according to claim 1, wherein the canceling sound forming means is composed of an adaptive filter circuit. 3. The mounting member has a shape that is locked to the auricle at the ear canal entrance, and the sound emitting means and the residual detection are provided on the surface side of the mounting member facing the ear canal. The noise reduction device according to claim 1 or 2, wherein the noise reduction device and the microphone are attached at positions spatially separated from each other. 4. The mounting member has an insertion portion to be inserted into the ear canal, the insertion portion includes a hollow portion, and the sound emitting means emits the cancellation sound through the hollow portion. The noise reduction device according to claim 1 or 2, wherein the noise detection microphone is attached to a position where noise residuals are collected in the hollow portion.