JP2002191089

Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2002191089
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
noise canceling microphone that cancels noise and faithfully converts only the voice of the user
into an electrical signal.
[0002]
2. Description of the Related Art As a conventional noise canceling microphone, a conventional
noise canceling electret condenser microphone is shown in FIG. In the noise cancellation type
electret condenser microphone, the diaphragm 12 is held in the acoustic case 11 in parallel with
the front plate 11 a. A front sound input hole 13 is formed in the front plate 11 a of the sound
case 11 facing the front surface of the diaphragm 12. On the other hand, a rear acoustic input
hole 14 is formed in the rear plate 11 b of the acoustic case 11 facing the rear surface of the
diaphragm 12. Further, in the acoustic case 11 on the back surface side of the diaphragm 12, an
electret capacitor element 15 is provided in proximity to the back surface of the diaphragm 12.
The electrode 16 of the electret capacitor element 15 penetrates the back plate 11 b of the
acoustic case 11 and is led to the outside.
[0003]
Such noise-cancelled electret condenser microphones can cancel noise and faithfully convert only
05-05-2019
1
the user's voice into an electrical signal. That is, noise generated around the microphone enters
the acoustic case 11 from the front acoustic input hole 13 of the acoustic case 11 and reaches
the front of the diaphragm 12, and from the rear acoustic input hole 14 of the acoustic case 11.
It enters into the acoustic case 11 and reaches the back surface of the diaphragm 12. Therefore,
the noises become equal in level at the front and back of the diaphragm 12 and cancel each
other, that is, they are canceled. As a result, the diaphragm 12 does not vibrate in noise, and the
electret capacitor element 15 is not output as an electrical signal.
[0004]
On the other hand, since the voice of the microphone user is generated near the front of the
microphone, it enters the acoustic case 11 from the front acoustic input hole 13 of the acoustic
case 11 and reaches the front of the diaphragm 12. Therefore, in the voice of the user, a
difference occurs in the sound level between the front and back surfaces of the diaphragm 12,
and the diaphragm 12 vibrates according to the level difference. As a result, the voice of the user
is converted into an electric signal by the capacitance change of the capacitor by the diaphragm
12 and the electret capacitor element 15, and is output as an electric signal from the electrode
16 of the electret capacitor element 15.
[0005]
What is important in such a noise cancellation type electret condenser microphone is that the
levels of the noises entering from the front acoustic input hole 13 and the rear acoustic input
hole 14 of the acoustic case 11 match at the front and back of the diaphragm 12 . Otherwise, the
noise is not canceled, the diaphragm 12 vibrates, and an electrical signal due to the noise is
output.
[0006]
However, in the conventional noise canceling electret condenser microphone as described above,
the electret condenser element 15 (acoustic-electrical conversion unit) having a large volume in
the acoustic case 11 on the back side of the diaphragm 12 Is housed in the back of the acoustic
case 11 and is a major obstacle to noise coming from the back acoustic input hole 14 of the
acoustic case 11, so that the level of the back of the diaphragm 12 is also 10 minutes to the level
of the front of the diaphragm 12 There is a problem that the noise level will be 1 or less, that is,
there is a difference in noise level between the front and back of the diaphragm 12, so that
cancellation of the noise becomes insufficient and an electrical signal due to the noise is output.
05-05-2019
2
The
[0007]
FIG. 4 is a characteristic diagram of the noise cancellation type electret condenser microphone. If
the electret condenser element 15 is not present, the input pattern a on the front of the
diaphragm regarding noise and the input pattern b on the back of the diaphragm become the
same. The presence of the capacitor element 15 weakens the input pattern on the back surface of
the diaphragm as c, and the difference from the input pattern a on the front surface of the
diaphragm becomes a non-cancellation component and is converted into an electric signal.
[0008]
Although the microphone includes, for example, a dynamic microphone in addition to the electret
condenser microphone, even with this dynamic microphone, instead of the electret condenser
element, a large volume induction coil element is accommodated in the acoustic case on the back
surface of the diaphragm. Since the induction coil element is an obstacle to noise input from the
rear side of the acoustic case, cancellation of noise is insufficient and there is a problem that an
electrical signal of noise is output.
[0009]
The present invention has been made in view of the above-mentioned point, and an object of the
present invention is to provide a noise cancellation type microphone capable of sufficiently
canceling noise and preventing output of an electric signal due to noise.
[0010]
In the noise canceling microphone of the present invention, a diaphragm is provided in an
acoustic case, and an acoustic input hole is formed in a front plate of the acoustic case opposed
to the front surface of the diaphragm. An acoustic input hole is also formed in an acoustic case
portion on the back side of the diaphragm, and a light emitting element for irradiating light to the
diaphragm as an acoustoelectric conversion unit in the acoustic case on the back side of the
diaphragm, and the light emitting element And a light receiving element for receiving the light
reflected from the diaphragm and converting the light into an electric signal.
[0011]
In the noise canceling microphone, specifically, the acoustic input hole on the back surface side
05-05-2019
3
of the diaphragm is formed in the back plate of the acoustic case facing the back surface of the
diaphragm and the side plate of the acoustic case.
In addition, a cylindrical cavity hood can be provided on the front side at the outer peripheral
end of the front plate of the acoustic case.
[0012]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the attached
drawings, embodiments of the noise canceling microphone according to the present invention
will be described in detail.
FIG. 1 is a view showing an embodiment of a noise canceling microphone according to the
present invention, wherein (a) is a longitudinal sectional view, (b) is a rear view, and (c) is a side
view.
In the noise cancellation type microphone shown in these figures, the diaphragm 32 is held in
parallel to the front plate 31 a in the cylindrical container-like acoustic case 31.
A front sound input hole 33 is formed in a circular shape at the center of the front plate 31 a of
the sound case 31 facing the front surface of the diaphragm 32.
In addition, a cylindrical cavity hood 34 is provided on the front end of the front plate 31 a of the
acoustic case 31 so as to protrude forward.
[0013]
On the other hand, a rear acoustic input hole 35 is formed in the rear plate 31 b of the acoustic
case 31 facing the rear surface of the diaphragm 32. As this back side acoustic input hole 35, as
shown in FIG. 1 (b), two long elongated acoustic input holes 35a are formed inside, and two short
elongated acoustic input holes 35b are formed outside them. Ru. Further, a side acoustic input
hole 36 is formed in the side plate 31 c of the acoustic case 31 on the back side of the
05-05-2019
4
diaphragm 32. As the side acoustic input holes 36, as shown in FIG. 1C, a plurality of elliptical
acoustic input holes 36a are formed at predetermined intervals in the circumferential direction of
the acoustic case 31.
[0014]
A light emitting element 37 and a light receiving element 38 are provided as an acoustoelectric
conversion unit inside the acoustic case 31 on the back side of the diaphragm 32. The light
emitting element 37 emits light to the back surface of the diaphragm 32. The light receiving
element 38 receives the reflected light emitted from the light emitting element 37 and reflected
by the back surface of the diaphragm 32, and converts the reflected light into an electric signal.
The light emitting element 37 and the light receiving element 38 are held on the substrate 39.
The light emitting element 37 and the electrode 40 of the light receiving element 38 pass
through the back plate 31 b of the acoustic case 31 and are led out.
[0015]
In the noise canceling microphone configured as described above, light is emitted from the light
emitting element 37 to the back surface of the diaphragm 32, while the light receiving element
38 receives the reflected light of the light reflected by the back surface of the diaphragm 32. And
converted into electrical signals. Therefore, when the diaphragm 32 vibrates with the voice of the
microphone user, the reflected light is modulated according to the vibration, and the modulated
reflected light is received by the light receiving element 38 and converted into an electrical
signal. An electrical signal corresponding to the voice is output from the light receiving element
38.
[0016]
Usually, the voice of the microphone user is generated near the front of the microphone, so the
sound enters the acoustic case 31 from the front acoustic input hole 33 of the acoustic case 31
and reaches the front of the diaphragm 32. Therefore, in the voice of the user, a difference
occurs in the acoustic level between the front and back surfaces of the diaphragm 32, and the
diaphragm 32 vibrates according to the level difference, and as a result, the light receiving
element using light as described above An electrical signal is output from 38.
05-05-2019
5
[0017]
On the other hand, the noise generated around the microphone enters the acoustic case 31
through the front acoustic input hole 33 of the acoustic case 31 and reaches the front of the
diaphragm 32, and the rear acoustic input hole of the acoustic case 31 It enters into the acoustic
case 31 from the side acoustic input holes 36 and 35 and reaches the back of the diaphragm 32.
Therefore, the noises become equal in level at the front and back of the diaphragm 32 and cancel
each other, that is, they are canceled. As a result, the diaphragm 32 does not vibrate due to noise,
and the reflected light is not modulated, so that an electrical signal is not output from the light
receiving element 38.
[0018]
At this time, in the noise cancellation type microphone described above, only the light emitting
element 37 and the light receiving element 38 of several mm square are accommodated in the
acoustic case 31 on the back surface side of the diaphragm 32, and the acoustics accommodated
in the same portion The volume of the electrical conversion unit can be reduced to about 1/10 or
less of that of the conventional electret capacitor element or induction coil element, so that it
enters the acoustic case 31 from the back surface side of the diaphragm 32 and reaches the back
surface of the diaphragm 32 Noise is not disturbed by the acoustoelectric conversion unit, and
the noise reaches the rear surface of the diaphragm 32 with a sufficient level. Therefore,
according to the noise cancellation type microphone described above, even if the acoustoelectric
conversion unit (the light emitting element 37 and the light receiving element 38) is
accommodated in the acoustic case 31 on the back surface of the diaphragm 32, as shown in FIG.
The input pattern a on the front of the diaphragm and the input pattern b on the rear of the
diaphragm regarding noise become the same, noise can be sufficiently canceled, and output of an
electrical signal due to noise can be prevented.
[0019]
Moreover, according to the noise cancellation type microphone described above, the side surface
plate 31 c of the acoustic case 31 also has the side sound input hole 36 on the back side of the
diaphragm 32 and sufficient cancellation is also made regarding noise input from the side
direction. It is possible. In the conventional noise canceling electret condenser microphone
shown in FIG. 3, the cancellation for the noise input from the side direction is generally 6 to 8 dB,
05-05-2019
6
but according to the noise canceling microphone of the present invention, the noise input from
the side direction It is possible to obtain cancellation of 25 dB or more. Therefore, the noise can
be canceled regardless of the direction.
[0020]
Further, according to the above noise cancellation type microphone, by having the cavity hood
34 at the outer peripheral end of the front plate 31a of the acoustic case 31, the directivity in the
front direction can be improved, and the voice of the user can be made efficient. Can be
converted into electrical signals. As a result of improving the directivity in the front direction, the
noise picked up from the front direction can be canceled by the balance with the noise input
inputted from the side sound input hole 35 of the sound case 31.
[0021]
As described above in detail, according to the noise cancellation type microphone of the present
invention, it is possible to securely prevent noise from being output and sufficiently canceling
noise.
05-05-2019
7