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DESCRIPTION JPH02246599

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DESCRIPTION JPH02246599
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
noise suppression microphone system for capturing a signal 'S / N well in an environment where
external noise enters. [Prior Art] For example, articles (Wlllias ^, Harr1son et al., 'ANew ^
pplicatlon or Adap ve No1se Cancallatlon', 1 [! ???? ASSP Vol ASSP-34 No, Feb, 1986 P, 21
to 27) introduces a method for extracting an S / N signal of an audio signal surrounded by an
acoustic barrier with good S / N. FIG. 5 is a block diagram showing a noise suppression
microphone system when it is applied to a car. In the above-mentioned article, the noise is the
engine noise and wind noise of the jet, the acoustic barrier is an oxygen mask, but in the case of a
car, the noise is considered to be a running noise and the acoustic barrier is a car body or a glass
portion. In FIG. 5, ? indicates a microphone attached to the outside of the windshield 4, 2 a
microphone attached to the inside of the windshield 4, and 3 synthesizes the output signals P
and r of the microphone 1.2 to produce one output. Reference numeral 8 denotes a connector for
connecting the output signal 2 to in-vehicle devices. Further, 5 is a car body, 6 is a driver who is
a speaker, 7 is a seat, W1 is an outer running noise, and S is a voice signal uttered by the driver
6. Next, the operation will be described. In hand-free car telephones and voice control systems, it
is important to capture the voice of the user to the traveling noise W with a high S / N ratio. FIG.
6 is a diagram showing an input state of voice and noise entering the microphone 2 and the
microphone l. When the driver 6 utters a voice, the output signal P, r of the microphone 1 ░ 2 is
expressed by the following equation. ??????? ??????? Here, IW. Audio signal
directly input to the microphone 2, noise signal directly input to the two microphones 1, audio
signal input to the microphone 1 through the windshield 4, noise signal input to the microphone
2 through the windshield 4. Due to the sound insulation of the windshield 4, the output signal P
is a signal centered on voice and r is a signal centered on noise. FIG. 7 is a block diagram
showing the function of the synthesis circuit. In FIG. 7, 21 is an adaptive filter, and 22 is an
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adder. The adaptive filter 21 is composed of, for example, a 100-tap FIR (finite impulse response)
filter, and the filter coefficients have the value of Z according to a known LMS (Least-meansquares) algorithm as described in the above-mentioned article. Is updated to be smaller (to
become
The noise component in the signal P is adaptively canceled by the output signal Y of the adaptive
filter 21 by the LMS algorithm to produce the output signal Z. As described above, in this
conventional example, the microphone 2 and the microphone l separate the acoustic barrier of
the windshield 4 and the distance between both microphones is as short as about 2011, so the
conditions shown in the above-mentioned article are satisfied and few taps The noise
components could be removed with a number of FIR filters. [Problems to be Solved by the
Invention] Since the conventional noise suppression microphone system is configured as
described above, in the environment where the microphone l outside the windshield 4 receives
wind pressure, the outside microphone l itself receives There is a problem that noise is newly
generated by wind noise and the noise suppression capability is reduced. The present invention
has been made to solve the above-mentioned problems, and it is an object of the present
invention to obtain a noise suppression microphone system having high noise suppression
capability even under an environment subjected to wind pressure. [Means for Solving the
Problems] The noise suppression microphone system according to the present invention
separates the outer and inner spaces by bringing them into close contact with a wall surface or
the like, and provides the container having sound insulation, and the outer and inner sides of this
container. And a means for combining the outputs of the two microphones. [Operation] The
container in the present invention has a sound insulation property of a predetermined level or
more, and noise noise intruding from the outside of the wall is inputted to the microphone inside
and outside the container at the same level, and the sound coming from outside the container
inside the wall Acts to reduce the sound pressure level input to the microphones in the container,
and the combining means operates to remove noise components from the signals from both
microphones. Embodiments of the noise suppressing microphone system of the present invention
will be described below with reference to the drawings. FIG. 1 is a configuration explanatory view
showing the entire configuration of one embodiment of the present invention. In FIG. 1,
microphones 1 and 2, a composite circuit 3, a windshield 4, a car body 5, a driver 6, and a seat 7
are shown. Connector 8, output signal P, r. Z is the same as in FIG. A container 9 is in close
contact with the windshield 4 and is a container made of hard glass with a radius of 5C11 for
sealing the microphone 1. The connector 10 connects the microphones 1 and 2 with the
composite circuit 3. FIG. 2 is an enlarged sectional view of a portion of the container 9. As shown
in FIG. 2, the container 9 is formed in a hemispherical shape with a radius of 5 cm, and the
periphery of the open end is formed to have a flat collar.
The flange portion is fixed to the windshield 4 with the adhesive rubber 11. An adhesive is
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applied to one side of the adhesive rubber 11, and the container 9 is fixed to the windshield 4
with the adhesive rubber 11 by this adhesive. Since the adhesive rubber 11 is made of a
plastically deformable material, the container 9 can be adhered to any position of the windshield
4. A microphone l is fixed to the outside of the container 9 (that is, the side facing the front glass
4) with a fixing rubber la via an adhesive. Similarly, the microphone 2 is fixed to the inner side
(that is, the side of the driver 6) of the container 9 via the adhesive by means of the fixing: fA2a.
The inside of the container 9 is a space, and a hole is provided through the cable led out from the
microphone 1, and after the cable from the microphone 1 is penetrated through this hole, the
hole is used as a sealing putty 12. Closed. The cable derived from the microphone 1.2 is
connected to the connector 10, and the connector 10 is connected to the input end of the
combining circuit 3 shown in FIG. Thereby, the output signal P of the microphone 1.2. r is to be
input to the synthesis circuit 3. The distance between the microphones 1 and 2 is approximately
21. Next, the operation will be described. FIG. 3 is an explanatory view showing an input state of
voice and noise entering the microphone 1.2. In FIG. 3, when the driver 6 utters a voice, the
output signals P and r of the microphone 1.2 are expressed by the following equations. P ? Ss +
W 4 r ? S a + W s where S. Voice signal directly input to the microphone 2, W; noise signal input
to the microphone 1 through the windshield 4 audio signal input to the microphone 1 through
the 34s container 9 W4: windshield 4 The noise signal that is input to the microphone 1 through
the window, but the noise signal that enters the container 9 from the inside of the container 9
through the windshield 4 and further enters the microphone 2 in the vehicle compartment has a
sound insulation characteristic of the container 9 of 6 dB or more Because it is smaller than the
noise signal W4, it is ignored. Similarly, the noise signal of the container 9 is 6 dB or more and is
smaller than the noise signal W because the noise signal passing through the windshield 4 and
entering the vehicle compartment and further from inside to outside of the container 9 into the
microphone 1 is also 6 dB or more. ignore. The synthesis circuit 3 operates to remove noise
components from the output signal P of the microphone centered on the voice signal and the
output signal r of the microphone centered on the noise signal as in the prior art, and produces
the output signal Z.
In the above embodiment, the container 9 is attached to the vehicle interior, and the microphone
1.2 is attached to the container 9, but the container 9 is attached to the outside of the windshield
4 as shown in FIG. , And the microphone 1.2 may be attached with the windshield 4 held
therebetween. In the above embodiment, the container 9 has a hemispherical shape with a radius
of 5 cm. However, if the space inside and outside of the container 9 can be separated, it is not
limited to any size and shape. Furthermore, in the above embodiment, the material of the
container 9 is hard glass, but it may not be hard glass as long as it has a sound insulation of 6 dB
or more. In the above embodiment, the system of the present invention is applied to a car, but
the application is not limited to that for a car, and it is also applicable to household glass, ships,
aircraft and the like. Furthermore, in the above embodiment, although one microphone 1.2 is
provided at each of the inside and the outside of the container 9, a plurality of microphones may
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be provided, and the microphones l and 2 of the inside and the outside of the container 9 may be
provided. Although the distance was 2 cm, it does not care about the direction and distance of
the microphone. As described above, according to the present invention, the inside and the
outside are separated by a container made of a sound insulating material and in close contact
with the wall surface, and microphones are installed on the inside and the outside of the
container. Since the noise suppression microphone system is configured, there is an effect that
the sound signal in the wall surface can be output with a good S / N ratio against the noise
intruding from the outside of the wall surface without being affected by the wind noise.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a block diagram showing the configuration of a noise suppression microphone system
according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view
showing in detail the structure of the container in the embodiment above, and FIG. 3 is the
microphone in the embodiment above FIG. 4 is a cross-sectional view showing the structure of a
container in the noise suppression microphone system according to another embodiment of the
present invention, and FIG. 5 is a block showing a conventional noise suppression microphone
system. FIG. 6 is an explanatory view showing the situation of human power to voice and noise
microphones in the conventional noise suppression microphone system, and FIG. 7 is a block
diagram showing the function of the conventional synthesis circuit.
1.2 иии Microphone, 1 a, 2 a иии Microphone fixed rubber, 3 и и и Composite circuit, 4 и и и и и и и и и и 9
container, 11 и и и adhesive rubber band, figure Among them, the same reference numerals
indicate the same or corresponding parts.
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