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JP2014033301

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DESCRIPTION JP2014033301
Abstract: [Problem] To provide a contact type microphone which is easy to pick up sound due to
skin conduction and hard to pick up external noise without causing decrease in productivity and
difficulty in mass production. A contact type microphone for converting vibration of a soft tissue
of a human body by transmitted sound into an electric signal and collecting the electric signal,
which functions as a vibration transmitting medium, and a plurality of films are separated in
front of the diaphragm 13 It is characterized in that a multilayer film 16 is disposed. Since
silicone is not used as the vibration transmission medium, problems such as the decrease in
productivity and the difficulty in mass production can be avoided. In addition, when the pickup
surface 11a is brought into contact with the skin 20, the film 16-1 vibrates integrally with the
skin 20 and therefore the transmission loss can be ignored, and the skin conduction sound is
transmitted through the film 16-2 and the diaphragm 13 It is transmitted to. On the other hand,
when the pickup surface is not in contact with the skin, the respective films prevent airborne
sound from infiltrating, thereby providing a sound insulation effect on noise. [Selected figure]
Figure 1
Contact microphone
[0001]
The present invention relates to a contact type microphone for acquiring a sound (skin
conduction sound) transmitted through soft tissue of a human body.
[0002]
Conventionally, in a contact type microphone, a structure is generally used in which the front
chamber of the diaphragm is filled with silicone having an acoustic impedance substantially
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equivalent to that of human soft tissue as a vibration transmission medium, and the surface of
this silicone is used as a pickup surface of skin conduction sound. (See, for example, Patent
Document 1).
[0003]
That is, for example, as shown in FIG. 6A, the contact type microphone 1 is housed in the case 2
similarly to the case 2 made of resin or the like, the diaphragm (diaphragm) 3 housed in the case
2 And a vibration / electricity conversion element 4 for converting the vibration of the
diaphragm 3 into an electric signal.
[0004]
The case 2 has a cylindrical shape with a bottom, and a diaphragm front chamber 2a is formed in
front of the diaphragm 3, and vibration due to sound transmitted through the skin 10 which is
soft tissue of the human body (skin conduction sound) is taken from the pickup surface 1a. An
opening 2 b for transmission to the diaphragm 3 is formed.
[0005]
The pickup surface 1a to the diaphragm front chamber 2a are filled with silicone 5 having an
acoustic impedance substantially equal to that of the soft tissue of the human body.
The silicone 5 acts as a medium for transmitting skin conduction sound to the diaphragm 3 by
bringing the pickup surface 1 a into contact with the skin 10.
On the other hand, the airborne sound is attenuated when entering the silicone 5 from the
pickup surface 1a as shown in FIG. 6B, and the transmission to the diaphragm 3 is blocked or
suppressed.
[0006]
In this way, by filling the diaphragm front chamber 2a with silicone 5, the acoustic impedance is
matched with the soft tissue of the human body to make it easy to pick up the vibration at the
time of contact, and it is difficult to pick up the airborne sound at the time of noncontact. A range
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can be secured.
The vibration caused by the skin conduction sound transmitted to the diaphragm 3 through the
silicone 5 is converted into an electric signal by the vibration-electric conversion element 4 and
collected.
[0007]
Unexamined-Japanese-Patent No. 2007-101305
[0008]
However, in the contact type microphone configured as described above, when filling the silicone
5 in the diaphragm front chamber 2a, use the silicone 5 as a vibration transmission medium,
such as mixing of air bubbles, securing of curing time, introduction of dedicated filling
equipment, etc. Problems such as a decrease in productivity and the difficulty of mass
production.
[0009]
On the other hand, if the silicone 5 is not used, air-borne sound is transmitted from the pickup
surface 1a to the diaphragm 3 via the silicone 5 in a state where the contact type microphone 1
is not in contact with the skin, picking up external noise. Become.
[0010]
The present invention has been proposed in view of the above, and an object of the present
invention is a contact that is easy to pick up sound by skin conduction and hard to pick up
external noise without causing a decrease in productivity or difficulty in mass production.
Providing a microphone.
[0011]
In order to solve the above-mentioned problems, a contact type microphone of the present
invention according to claim 1 is a contact type microphone which converts vibration by sound
transmitted to soft tissue of a human body into an electric signal and collects the electric signal,
The multilayer film 16 functions as a vibration transmission medium, and a plurality of films are
disposed in front of the diaphragm 13 so as to be separated from each other.
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[0012]
The invention according to claim 2 is the contact type microphone according to claim 1, the case
12 for accommodating the diaphragm 13 and the vibration electric conversion for
accommodating the vibration of the diaphragm 13 into the electric signal, which is
accommodated in the case 12 And means (14).
[0013]
The invention according to claim 3 is the contact-type microphone according to claim 1 or 2,
wherein the multilayer film 16 comprises first and second films 16-1 and 16-2, and the first and
second films. A first spacer 17-1 interposed on an outer peripheral portion between the films 161 and 16-2 and separating the first and second films 16-1 and 16-2 by a predetermined distance;
And a second spacer 17-2 interposed between the outer periphery of the second film 16-2 and
the case 12 and separating the second film 16-2 and the case 12 at a predetermined interval. The
first film 16-1 is brought into contact with the skin 20 and collected.
[0014]
According to the contact type microphone of the present invention, since silicone is not used as
the vibration transfer medium, it is possible to avoid the problems such as the decrease in
productivity and the difficulty of mass production due to the use of silicone.
Also, when the pickup surface is in contact with the skin, the film in close contact with the skin of
the multilayer film vibrates integrally with the skin, so transmission loss due to this film can be
ignored and the skin conduction sound is in close contact with the skin It is transmitted to the
diaphragm through the film other than the film.
On the other hand, when the pickup surface is not in contact with the skin, the respective films of
the multilayer film prevent the infiltration of the airborne sound, so that the sound insulation
effect on the noise works.
[0015]
Accordingly, it is possible to provide a contact type microphone that is hard to pick up airborne
sound (external noise) and easy to pick up skin conduction sound (voice) without causing a
decrease in productivity or difficulty in mass production.
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[0016]
The structural example of the contact-type microphone which concerns on embodiment of this
invention is shown, (a) A sectional view in case a skin conduction sound is picked up, (b) A figure
for explaining attenuation of air propagation sound. FIG.
It is a characteristic view showing the measurement result of the sensitivity to the frequency of
the skin conduction sound (sound) in the case of one film and two films.
It is a characteristic view showing the measurement result of the sensitivity to the frequency of
the airborne sound (external noise) in the case of one film and two films.
It is a figure which compares and shows the range width, the skin conduction sound, and the
airborne sound in the case of one film and two films, respectively.
It is a figure which compares and shows skin conduction sound and air propagation sound in a
contact type microphone concerning conventional and an embodiment of the present invention.
The example of a structure of the conventional contact type microphone is shown, (a) A figure is
sectional drawing in the case of collecting skin conduction sound, (b) A figure is sectional
drawing for demonstrating attenuation | damping of airborne sound.
[0017]
Hereinafter, an embodiment of the present invention will be described based on the drawings.
[0018]
FIG. 1A is a cross-sectional view showing a configuration example of a contact type microphone
according to an embodiment of the present invention.
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The contact type microphone 11 makes the pickup surface 11a contact the skin 20 which is a
soft tissue of a human body, for example, the neck or the lower part of an ear, and picks up skin
conduction sound.
[0019]
The contact type microphone 11 is housed in a case 12 made of resin or the like, a diaphragm
(diaphragm) 13 housed in the case 12 and a case 12 similarly to the conventional case, and
vibration of the diaphragm 13 is detected. A vibration / electricity conversion element (vibration
/ electricity conversion means) 14 for converting into an electric signal is provided.
For example, an electret or a piezoelectric element (piezo element) can be used as the vibrationelectric conversion element 14.
[0020]
The case 12 has a cylindrical shape with a bottom, and a diaphragm front chamber 12a is formed
in front of the diaphragm 13 to transmit vibration due to the sound transmitted from the skin 20
which is soft tissue of the human body to the diaphragm 13 from the pickup surface 11a. An
opening 12b is formed.
[0021]
On the side of the pickup surface 11 a of the case 12, a multilayer film 16 serving as a vibration
transmission medium for transmitting skin conduction sound to the diaphragm 13 is provided.
In this embodiment, the multilayer film 16 includes the first and second films 16-1 and 16-2 and
a spacer 17-1 interposed in the outer peripheral portion between the films 16-1 and 16-2. And a
second spacer 17-2 interposed in the outer peripheral portion between the second film 16-2 and
the case 12.
[0022]
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The first and second films 16-1 and 16-2 are respectively made of a resin such as PET
(polyethylene terephthalate) or ABS (acrylonitrile butadiene styrene), a metal such as SUS
(stainless steel), or a combination thereof The preferred thickness is in the range of 25 μm to 3
mm.
Similarly, the spacers 17-1 and 17-2 may be made of resin such as PET or ABS, metal such as
SUS, double-sided tape such as non-woven fabric with adhesive, or a combination of these, and
preferred thickness Is in the range of 0.1 mm to 3 mm. Here, the diameter of the opening 12 b of
the case 12 is 0.1 mm or more.
[0023]
Then, the pickup surface 11a is brought into contact with the skin 20, and the vibration due to
the sound transmitted to the soft tissue of the human body (skin conduction sound) is
transmitted to the diaphragm 13 via the multilayer film 16 and the vibration electric conversion
element 14 Convert to an electrical signal and pick it up.
[0024]
In the above configuration, when the pickup surface 11a is in contact with the skin 20, the film
16-1 in close contact with the skin 20 vibrates integrally with the skin 20 and the skin
conduction sound is a film other than the film 16-1. 16-2 is transmitted to the diaphragm 13.
Thus, since the transmission loss of the film 16-1 can be ignored by moving the skin 20 and the
film 16-1 integrally, the sound by skin conduction becomes easy to pick up.
[0025]
On the other hand, when the pickup surface 11a is not in contact with the skin 20, as shown in
FIG. 1 (b), the multilayer film 16 (films 16-1 and 16-2) disposed in front of the diaphragm 13 has
external noise. Sound insulation effect works because it prevents intrusion. That is, in view of the
mass law of sound insulation, when the airborne sound passes through the medium (films 16-1
and 16-2), there is a transmission loss (effect of reducing the sound pressure). The effect is
known to be proportional to mass and density from the following equation (1). Transmission loss
= 20 log (area density × frequency) −43 [dB] (1)
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[0026]
As described above, by providing the multilayer film 16 on the front surface of the diaphragm
13, although having a relatively simple structure, air-borne noise (external noise) entering the
contact microphone 11 more than conventional silicone-filled type It can be prevented, and skin
conduction sound can get the same gain as silicone filled type.
[0027]
In addition, since it is not necessary to use silicone as a vibration transmission medium, problems
such as mixing of air bubbles, securing of curing time, introduction of dedicated equipment for
filling, productivity decrease due to using silicone and difficulty of mass production etc. Can be
avoided.
[0028]
As a result, it is difficult to pick up the airborne sound (external noise) and produce a contact
microphone that is easy to pick up the skin conduction sound (voice) without causing a decrease
in productivity or difficulty in mass production.
[0029]
The present inventors conducted a demonstration experiment of skin conduction sound (voice)
and airborne sound (external noise) by the contact type microphone.
In this experiment, PET films having a diameter of about 6 mm and a thickness of 50 μm were
used for the films 16-1 and 16-2, respectively, and the thickness of the spacers 17-1 and 17-2
was about 0.5 mm.
[0030]
Fig. 2 is a characteristic diagram showing the measurement results of the sensitivity to the
frequency of skin conduction sound (voice) in the case of one film and two films, and Fig. 3 is the
measurement of the sensitivity to the frequency of airborne sound (external noise) It is a
characteristic view showing a result.
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As shown by the dashed-dotted line (monolayer) 30 and the solid line (multilayer) 40 in FIG. 2, it
can be seen that the skin conduction sound can maintain the same sensitivity as the single layer
in each frequency band even if the film is multi-layered.
[0031]
On the other hand, as indicated by the alternate long and short dash line 30 and the solid line 40
in FIG. 3, in the frequency band of 3.4 KHz or less, the airborne sound has lower sensitivity in the
case of multiple layers compared to a single layer.
Since the actual use band is a frequency of about 300 Hz to about 3.4 KHz, it can be understood
that it is difficult to pick up the noise by using a multilayer.
[0032]
FIG. 4 is a view comparing the range width, the skin conduction sound and the airborne sound in
the case of one film and in the case of two films. In FIG. 4, hatched bar-like regions 51 and 52
represent range widths, 61 and 62 represent gain [dBV] of skin conduction sound, and 71 and
72 represent gain [dBV] of airborne sound. As can be seen from FIG. 4, the external noise value
(airborne sound) decreases by 13 [dBV] by using a multilayer (here, two-layer) film, but the
sound sensitivity (skin conduction sound) is only 3 [dBV]. It has not fallen. That is, it was
confirmed that the sound was a skin conduction microphone which was easy to pick up and
external noise was hard to pick up.
[0033]
FIG. 5 shows by comparison the skin conduction sound and the airborne sound in the contact
microphones according to the prior art and the embodiment of the present invention filled with
silicone. In FIG. 5, the range width, the skin conduction sound, and the average value of the
airborne sound are shown at a frequency of about 300 Hz to 3.4 KHz. Further, in FIG. 5, the
hatched bar-like regions 51 and 52 represent the range width, 61 and 62 represent the gain
[dBV] of the skin conduction sound, and 71 and 72 represent the gain [dBV] of the airborne
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sound. .
[0034]
As apparent from FIG. 5, the sensitivity performance of the skin conduction sound is almost the
same, and the sensitivity of the airborne sound is lower in the contact type microphone of the
present invention than in the conventional product, so that it is confirmed that it is resistant to
noise.
[0035]
Therefore, according to the present invention, it is possible to provide a contact type microphone
which is easy to pick up sound due to skin conduction and hard to pick up external noise without
causing decrease in productivity and difficulty in mass production.
[0036]
The present invention is not limited to the above-described embodiment, and various
modifications can be made without departing from the scope of the invention.
For example, although the example which comprises the multilayer film 16 by a film of two
layers was shown, of course, three or more layers may be sufficient.
Further, not only the number of layers of the film but also the thickness of the spacer may be set
in accordance with the required acoustic characteristics.
[0037]
DESCRIPTION OF SYMBOLS 1, 11 Contact-type microphone 1a, 11a Pickup surface 2, 12 Case
2a, 12a Diaphragm front chamber 2b, 12b Opening 3, 13 Diaphragm 4, 14 Vibration electric
conversion element (vibration electric conversion means) 5 Silicone 16 Multilayer film 16 -1, 162 first and second films 17-1, 17-2 spacer 10, 20 skin 30 one-dot chain line 40 solid line 51, 52
rod-like area (range width) 61, 62 gain of skin conduction sound 71, 72 Gain of airborne sound
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