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JP2007300513

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DESCRIPTION JP2007300513
PROBLEM TO BE SOLVED: To provide a microphone device having flat frequency response
characteristics to a close proximity sound source. SOLUTION: A first microphone 7 and a second
microphone 8 forming a set are disposed in a spherical wave sound field generated by a
proximity sound source 9, and the first microphone 7 is set at a position approaching the
proximity sound source 9. The second microphone 8 is constructed to be far from the distance
between the microphone 7 and the proximity sound source 9. According to the above
configuration, it is possible to obtain flat frequency response characteristics with respect to the
proximity sound source, and further, it is possible to sufficiently secure the noise suppression
effect in the low frequency range. [Selected figure] Figure 3
Microphone device
[0001]
The present invention relates to a microphone device that improves frequency response to a near
sound source.
[0002]
The headset makes it easy for the speaker to make hands-free calls, and is widely used not only
for call center operators but also as an option for mobile phones and terminals for voice
communications via personal computers (PCs). .
[0003]
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1
The headset used in the call center is a microphone attached to the tip of an arm 23 extending
from the receiver 22 with the speaker 20 using the headband 21 to place the receiver 22 on the
ear of the speaker 20 as shown in FIG. 24 is positioned near the mouth, and the voice
information of the speaker 20 is picked up by the microphone 24, and is used when the speaker
talks with the other party.
The environment in which the headset shown in FIG. 13 is used is often an environment where
the influence of ambient noise is large.
In particular, in a call center, many operators are often arranged relatively closely in a room
without partitions, and the microphone of the headset of a particular speaker picks up the voices
of the operators before and after that. It occurs. In order to solve this problem, a close-talking
microphone capsule is used as a headset microphone, and the influence of ambient noise is often
reduced by the directivity and proximity effect of the microphone.
[0004]
An example of the close talk type microphone capsule is schematically shown in FIG. As shown in
FIG. 14, in the close talk type microphone capsule, the inside of the case 25 is divided into two
front and rear chambers by the diaphragm 26, the front sound hole 27 is opened in front of the
diaphragm 26, and The back sound hole 28 is configured to be open.
[0005]
A sound wave of wavelength λ incoming from the front side of the case 25 is drawn from the
front sound hole 27 of the case 25 into the case 25 and the sound pressure P1 of the sound
wave is applied to the front of the diaphragm 26. Further, a sound wave of wavelength λ coming
from the front side of the case 25 is diverted to the outside of the case 25 and drawn into the
case 25 from the back sound hole 28 of the case 25, and the sound pressure P 2 of the sound
wave is made of the diaphragm 26. It is acting on the back. The vibrating film 26 outputs an
output signal proportional to the difference between the sound pressures P1 and P2 acting on
the front and back surfaces.
04-05-2019
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[0006]
In the close-talking microphone capsule shown in FIG. 14, the frequency response of the far-field
sound field located at a distance of L = 1 m shows the response characteristic shown by the solid
line in FIG. On the other hand, the frequency response of the microphone capsule located at a
distance of L = 2.5 cm shows the response characteristic shown by the dotted line in FIG. 15, and
exhibits the noise suppression effect in the low frequency band.
[0007]
However, the sound environment of the call center varies widely, and the use of a close talk type
microphone capsule is not always effective at present.
In the use of the close talk type microphone capsule alone, as shown in FIG. 15, the output level
of the sound pressure in the low frequency range is insufficient compared to that in the high
frequency range, and the frequency response also shows a high frequency rise. Therefore, there
is a problem in terms of sound quality.
[0008]
Also, when considering a microphone device that whistle using a plurality of microphones
developed conventionally, it is classified into the type shown in FIG. 16 and the type shown in
FIG. As typical examples of prior art belonging to each type, microphone devices disclosed in JPA-8-213936, JP-A-9-327084, JP-A-5-256776, etc. are shown as types shown in FIG. included.
The type shown in FIG. 17 includes the microphone device disclosed in Japanese Patent No.
2897230. However, the microphone devices disclosed in these publications are a part, and the
microphone devices disclosed in many other publications have been developed.
[0009]
A microphone device of the type shown in FIG. 16 has been developed to stutter sound
information from a distant sound source, and combines a first microphone 30 and a second
microphone 31.
[0010]
A microphone device of the type shown in FIG. 16 is used for a video tape recorder or the like,
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and as an environment surrounding the microphone device, a noise source emitted from the
video tape recorder is present at a short distance and noise is generated at a distant distance.
There is a sound source of stuttering sound emitted by the person to be photographed.
[0011]
A microphone device of the type shown in FIG. 16 is attached as an accessory such as a video
tape recorder, and the video tape recorder is miniaturized to the size of a photographer's palm.
Therefore, as the size of the microphone device, a miniaturized size corresponding to the size of
the video tape recorder is required, and the distance d between the first microphone 30 and the
second microphone 31 is set as narrow as possible. There is.
Incidentally, the distance d is set to about 10 mm.
[0012]
Furthermore, the microphone device of the type shown in FIG. 16 is required to stutter the sound
information emitted by a person or the like in the far-field sound field, and to suppress the noise
generated from the video tape recorder in the near-field sound field. Is required. Therefore, as
shown in FIG. 16, the sound information generated by the second microphone 31 is subtracted
from the sound information generated by the first microphone 30, and only the sound
information from the sound source in the far-field sound field is generated. It is impossible to do.
[0013]
Therefore, as shown in FIG. 16, a directivity formation / frequency characteristic correction
circuit 32 is provided on the output side of the first microphone 30 and the second microphone
31. Then, the directivity formation / frequency characteristic correction circuit 32 stutters sound
information from the sound source of the far-field sound field, and forms directivity so as not to
stutter the noise of the near-field sound field. Furthermore, in order to improve the voice quality
of the sound information beaten by the directivity formation / frequency characteristic correction
circuit 32, the frequency characteristic is corrected.
04-05-2019
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[0014]
As described above, the microphone device of the type shown in FIG. 16 is limited in
miniaturization because the directivity formation / frequency characteristic correction circuit 32
is present. Further, in order to miniaturize the microphone device, it is necessary to set the
distance d between the first microphone 30 and the second microphone 31 as narrow as
possible.
[0015]
However, since the distance d between the first microphone 30 and the second microphone 31 is
determined by the upper limit value of the stutterable frequency range, setting the distance d
narrow means that the distance d The sensitivity in the main frequency band where energy is
concentrated is low, which in turn leads to deterioration of the sound quality of the sound
information to be stuttered.
[0016]
A microphone device of the type shown in FIG. 17 combines a first microphone 40 and a second
microphone 41 and sets the first microphone 40 to the mouth of the speaker 42 with a headset,
and the second microphone 41. Is set to a position where noise should be heard.
[0017]
The microphone device of the type shown in FIG. 17 is installed with the first microphone 40
placed close to the sound source to be beaten and the second microphone 41 is pulled away from
the sound source to be beaten and brought close to the noise source Therefore, in consideration
of the process of noise being transmitted to the first microphone 40, a transfer function
simulation circuit 43 estimates a transfer function of a path through which the noise is
transmitted to the first microphone. The sound information of the noise that is noised by the
second microphone 41 is delayed by the time corresponding to the transfer function estimated
by the transfer function simulation circuit 43, and the sound information of the noise is input to
the subtractor 44, A subtraction process is performed between the sound information that the
first microphone 40 threw and the noise information of the noise that the second microphone 41
threw, and the noise suppression effect It is necessary to secure.
[0018]
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5
As described above, the microphone device of the type shown in FIG. 17 has limitations in
achieving size reduction because the transfer function simulation circuit 43 and the subtractor
44 exist.
Furthermore, since the first microphone 40 and the second microphone 41 need to be placed
close to the noise source and noise sources of different characteristics, respectively, the first
microphone 40 and the second microphone 41 need to be installed. The distance d between the
two microphones 41 must be extremely wide, which also limits the reduction in size.
[0019]
As described above, when considering the characteristics of various microphone devices that
have been developed in the past, it is not possible to obtain flat frequency response
characteristics even for a proximity sound source, that is, there is a problem in the sound quality
of sound information, and low frequency There is a problem that the noise suppression effect in
the area is insufficient.
JP-A-8-213936 JP-A-9-327084 JP-A-5-256776 JP-B-2897230
[0020]
An object of the present invention is to provide a microphone device capable of obtaining a flat
frequency response characteristic with respect to a close proximity sound source and capable of
sufficiently securing a noise suppression effect in a low frequency range.
[0021]
In order to achieve the above object, a microphone device according to the present invention
arranges a first microphone and a second microphone forming a pair in a spherical wave field
generated by a proximity sound source, and the microphone device for the proximity sound
source It is characterized in that the frequency response is greatly improved.
[0022]
Specifically, in the microphone device according to the present invention, the first microphone
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and the second microphone forming a pair are disposed in a spherical wave field generated by a
proximity sound source, and the first microphone is brought close to the proximity sound source.
The second microphone is set at a distance relative to the distance between the microphone and
the near sound source.
[0023]
According to the present invention, since the first and second microphones forming a pair are
arranged in the spherical wave field generated by the proximity sound source, they need to be
considered in the case of the microphone device shown in FIG. Moreover, it is not necessary to
estimate the transfer coefficient of the path through which noise passes, and the transfer
function simulation circuit becomes unnecessary, and the structure of the microphone device can
be simplified.
Furthermore, the noise suppression effect can be obtained only by subtracting the sound
information output from the first microphone and the second microphone.
[0024]
Further, the first microphone is set at a position approaching the proximity sound source, and
the second microphone is set farther by comparison with the distance between the microphone
and the proximity sound source. The distance between the acoustic terminals, which is the
distance between the second microphone and the second microphone, can be kept relatively
wide, and the frequency response of the microphone device to the proximity sound source is
improved.
[0025]
Generally, the storable frequency range of the microphone is defined by the response to the
plane wave, so in the present invention, the distance between the acoustic terminals of the first
microphone and the second microphone is the sound pressure of the plane wave. It may be
determined based on the upper limit value of the stutterable frequency range.
[0026]
In setting the distance between the acoustic terminals, in addition to the determination based on
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7
the upper limit value of the frequency range in which noise can be generated by the sound
pressure of the plane wave as described above, the noise suppression amount is taken into
consideration.
When the noise suppression amount at 100 Hz is set to 30 dB or more, it is desirable to set the
distance d between acoustic terminals between the first microphone and the second microphone
in a range near 30 mm <d <50 mm It is a thing.
[0027]
Further, with regard to the arrangement of the microphones, the first microphone is arranged in
front of the proximity sound source, and the second microphone is arranged at a position
laterally shifted with respect to the position of the first microphone. Is also good.
Further, the first microphone and the second microphone may be arranged on a straight line with
respect to the proximity sound source.
[0028]
The microphone may be either nondirectional or directional, but from the viewpoint of
simplifying the configuration of the microphone device, the first microphone and the second
microphone are nondirectional. It is desirable to have stuttering characteristics.
[0029]
As described above, according to the present invention, since the first and second microphones
forming a pair are arranged in the spherical wave field generated by the proximity sound source,
transmission of a path through which noise passes as in the prior art There is no need to
estimate the coefficients, no transfer function simulation circuit is required, and the structure of
the microphone device can be simplified.
Furthermore, the noise suppression effect can be obtained only by subtracting the sound
information output from the first microphone and the second microphone.
04-05-2019
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[0030]
Further, the first microphone is set at a position approaching the proximity sound source, and
the second microphone is set farther by comparison with the distance between the microphone
and the proximity sound source. The distance between the acoustic terminals, which is the
distance between the second microphone and the second microphone, can be kept relatively wide
to improve the frequency response of the microphone device to the proximity sound source.
[0031]
Hereinafter, embodiments of the present invention will be described in detail based on the
drawings.
[0032]
Next, an example in which the microphone device according to the present invention is applied to
a microphone device of a headset will be described as an embodiment.
[0033]
Considering a headset used in a call center or the like, as shown in FIG. 1, in the headset, the
speaker 1 uses the head hand 2 to place the receiver 3 on the ear of the speaker 1 and an arm
extending from the receiver 3 The microphone device 5 attached to the tip of 4 is positioned in
the vicinity of the mouth 1a, the voice information of the speaker 1 is picked up by the
microphone device 5, and the speaker and the other party are used for conversation.
[0034]
In the environment where the headset shown in FIG. 1 is used, there are often a plurality of noise
sources 6 which become noise for the microphone device 5 of the speaker 1, which is often an
environment where the influence of noise is large.
In particular, in the call center, many operators are often arranged relatively closely in a room
without partitions, and the voices of the operators arranged at the front, back, left, and right with
respect to the microphone device 5 of the headset of the specific speaker Becomes a noise source
6, and there arises a problem that the microphone device 5 of the headset of a particular speaker
picks up the voices of other operators.
04-05-2019
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[0035]
The present invention is characterized in that it specializes in a spherical acoustic field generated
by a proximity sound source, obtains flat frequency response to the proximity sound source, and
sufficiently secures a noise suppression effect in a low frequency range. It is.
[0036]
The basic concept of ambient noise reduction in the present invention will be described.
An omnidirectional microphone generally used for a cellular phone or the like outputs a voltage
proportional to the sound pressure received by the sound hole provided on the front surface, and
is classified as a pressure type as a transducer type.
The sound pressure sensitivity of the nondirectional microphone does not depend on the
direction of arrival of the sound wave and the distance from the sound source of the microphone,
and therefore has no effect in terms of ambient noise reduction.
[0037]
On the other hand, close-talking microphones have two sound holes at the front and back of the
microphone capsule and are proportional to the difference in sound pressure received by these
sound holes. being classified.
[0038]
The close talk type microphone mechanically realizes the operation of taking the difference
between the sound pressure received by the front sound hole and the sound pressure received by
the back sound hole.
The sound wave received by the microphone can be treated as a plane wave (hereinafter referred
to as a far-field sound field).
04-05-2019
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The output of the pressure gradient microphone is proportional to the phase difference of the
sound waves at the front and back sound hole positions.
On the other hand, the case where the microphone is close to the sound source and the sound
wave received by the microphone is a spherical wave (hereinafter referred to as near-field sound
(spherical sound field).
In the above, in addition to the phase difference, the amplitude difference of the sound waves at
the front and back sound hole positions also becomes the pressure gradient.
[0039]
Therefore, since the amplitude difference contributes to the output of the microphone, the sound
pressure sensitivity of the close talk type microphone is larger in the near sound field than in the
far sound field, and this is called the proximity effect.
That is, if a close talk type microphone is placed at the speaker's mouth and used, it is difficult to
pick up sound waves emitted from a sound source far from the speaker, and ambient noise can
be reduced by the proximity effect of the microphone.
Assuming that the distance between the front and rear sound holes in the close talk type
microphone is a simple distance between the sound terminals, the reduction effect of the ambient
noise by the proximity effect depends on the distance between the sound terminals.
[0040]
However, as described in the section of the prior art, the conventional close talk type microphone
is for improving the frequency response to a sound source generating a far-field sound field, and
for the purpose of downsizing, the above-mentioned acoustic terminal The distance between
them is at most about 10 mm, and it is a fact that the microphone capsule alone can not expect
an ambient noise reduction effect more than the distance between the acoustic terminals.
[0041]
The present invention realizes a configuration in which two nondirectional microphones are
04-05-2019
11
combined to realize the frequency response possessed by the close talk type microphone and to
secure a relatively long distance between the acoustic terminals.
[0042]
In the embodiment of the present invention, as shown in FIG. 2 and FIG. 3, the nondirectional
first microphone 7 and the second microphone 8 constituting the microphone device 5 are
arranged in the spherical wave field generated by the proximity sound source 9. It has been
installed.
Here, when applied as the microphone device of the headset shown in FIG. 2 and FIG. 3, the
proximity sound source 9 is a voice (sound source) emitted by the speaker 1 and the spherical
wave field is the voice of the speaker 1 Is a sound field generated by propagation.
[0043]
Since the first microphone 7 and the second microphone 8 have no directivity, the sound
pressure sensitivity of the microphones 7 and 8 is the sound wave from the proximity sound
source 9 when arranged in the spherical wave sound field. And the distance from the sound
source 9 of the microphone.
Therefore, the microphones 7 and 8 output a large voltage signal when the sound level from the
proximity sound source 9 is high, and output a small voltage signal when the sound level is low.
[0044]
Further, the discussion will be focused on the microphones 7 and 8. In the microphone device 5
of the headset, a spherical wave sound field (near field sound field) generated at a near position
with respect to the near sound source 9 and a diagram different from the near sound source 9 at
a far distance position with respect to the near sound source 9 It will be simultaneously placed in
the far field generated by the noise source 6 shown in FIG. In the near field, there is a large
difference between the sound pressure levels picked up by the microphones 7 and 8.
04-05-2019
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[0045]
On the other hand, in the far field, the level difference between the sound information reaching
the microphones 7 and 8 is extremely small.
[0046]
In the embodiment of the present invention, the positional relationship between the first
microphone 7 and the second microphone 8 disposed in the spherical wave field is restricted in
order to improve the noise suppression effect using the characteristics described above. doing.
Specifically, as shown in FIGS. 2 and 3, the first microphone 7 is set at a position A approaching
the proximity sound source 9 in the spherical wave sound field. On the other hand, the second
microphone 8 is set at a position B distant from the distance between the microphone 7 and the
proximity sound source 9 in the spherical sound field.
[0047]
Since the first microphone 7 and the second microphone 8 are set in the positional relationship
shown in FIGS. 2 and 3, the output signal causes a difference in output signal. That is, since the
first microphone 7 is set at a position approaching the proximity sound source 9, the sound
pressure level of the sound information from the proximity sound source 9 is determined by the
second microphone 8 from the proximity sound source 9. Since the sound pressure level of the
sound information to be picked up is larger, a large voltage signal is output corresponding to the
sound information from the proximity sound source 9.
[0048]
Since the first microphones 7 and 8 are omnidirectional, they pick up not only the sound
information from the spherical wave field but also the sound information from the far field.
However, since the far-field is generated at a far-distance position away from the spherical wave
field, when the microphones 7 and 8 pick up sound information coming from the far-field, There
is almost no difference in the level of the sound information picked up by the microphones 7 and
8.
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[0049]
Therefore, as shown in FIG. 6B, the first microphone 7 generates a voltage signal S1 of a large
output value P1 corresponding to the sound information from the proximity sound source 9, and
the sound from the far-distance noise source 6 The voltage signal N1 of the output value P2
corresponding to the information is output. Further, as shown in FIG. 6C, the second microphone
8 has a voltage signal S2 of a relatively small output value P3 (P1 >> P3) corresponding to the
sound information from the proximity sound source 9, and The voltage signal N2 of the output
value P4 (P2 ≒ P4) corresponding to the sound information from the noise source 6 is output.
[0050]
Therefore, as shown in FIG. 6A, the subtractor 10 subtracts the voltage signals S2 and N2 output
from the second microphone 8 from the voltage signals S1 and N1 output from the first
microphone 7 As shown in FIG. 7 (b), the S / N ratio is significantly improved, and a flat response
characteristic to the proximity sound source 8 is obtained, and a noise suppression effect in a low
frequency range is sufficiently ensured. it can. For reference, in the case of the conventional
close-talking microphone, the output level for the near sound source is around -10 dB. It can be
seen that the power level in the embodiments of the present invention is significantly improved.
[0051]
Next, the distance d between acoustic terminals between the first microphone 7 and the second
microphone 8 will be described.
[0052]
Generally, the storable frequency range of the microphone is defined by the response to the
plane wave, so in the present invention, the distance between the acoustic terminals of the first
microphone 7 and the second microphone 8 is the sound of the plane wave. Determined based
on the upper limit of the frequency range that can be beaten by pressure.
Furthermore, in setting the distance between the acoustic terminals, in addition to the
04-05-2019
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determination based on the upper limit value of the frequency range in which noise can be
generated by the sound pressure of the plane wave as described above, the noise suppression
amount is taken into consideration. When the noise suppression amount at 100 Hz is set to 30
dB or more, it is desirable to set the distance d between acoustic terminals between the first
microphone and the second microphone in a range near 30 mm <d <50 mm It is a thing. I will
explain this basis.
[0053]
In the characteristic measurement of the microphone, in the microphone device according to the
embodiment of the present invention, the midpoint of the line connecting the first microphone 7
and the second microphone 8 is defined as the microphone position. FIG. 12 is a characteristic
diagram showing the relationship between the distance d between acoustic terminals, which is
the distance between the first microphone 7 and the second microphone 8, and the noise
suppression amount. In FIG. 12, the noise suppression amount is indicated by the sensitivity
difference of the microphone device at 100 Hz when the distance from the proximity sound
source to the microphone is 25 cm and 1 m. It can be seen that if the desired noise suppression
amount is 30 dB or more, it is set to at least about 30 mm or more of the distance between the
acoustic terminals. Further, according to the definition of the microphone device, since the first
microphone 7 and the proximity sound source are at the same position when the distance d
between the acoustic terminals is 50 mm or more, the upper limit of the distance d between the
acoustic terminals is less than 50 mm.
[0054]
An example of the distance d between the acoustic terminals is shown. Assuming that the
frequency band picked up by the microphones 7 and 8 is a telephone voice band, that is, 300 Hz
to 3.4 KHz, and the upper limit value of the frequency that can be muffled by the sound pressure
of the plane wave is around 4 KHz, the distance d between acoustic terminals obtained is 42. It
will be 5 mm. The distance d between the acoustic terminals is calculated by simulation. The
above numerical value is an example, and if the upper limit value of the stuttering frequency
changes with the sound pressure of the plane wave, it changes accordingly, and based on the
upper limit value of the frequency for the stuttering by the microphone device Set as appropriate.
The distance d between the acoustic terminals mentioned as an example in the embodiment of
the present invention is 42.5 mm, and the distance between the simple acoustic terminals of the
conventional close talk type microphone is 10 mm, while it is greatly expanded. I understand that
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[0055]
Next, an arrangement relationship between the first microphone 7 and the second microphone 8
will be described.
[0056]
As shown in FIG. 2, the first microphone 7 is disposed in front of the proximity sound source 9,
and the second microphone 8 is on a straight line connecting the proximity sound source 9 and
the first microphone 7. Place on
In this case, the first microphone 7 and the second microphone 8 are spaced apart by the
distance d between the acoustic terminals.
[0057]
Further, as shown in FIG. 3, the first microphone 7 is disposed in front of the proximity sound
source 9, and the second microphone 8 is laterally shifted with respect to the position of the first
microphone 7. It may be arranged at a position. Similarly in the case of FIG. 3, the first
microphone 7 and the second microphone 8 are placed apart by the distance d between the
acoustic terminals. In the example of FIG. 3, since the second microphone 8 is installed laterally
shifted, there is an advantage that the second microphone 8 does not get in the way of the
speaker 1 when attached to the headset and the feeling of use becomes good. doing.
[0058]
In the case of the positional relationship between the microphones 7 and 8 shown in FIGS. 2 and
3, when the frequency response is examined in relation to the proximity sound source 9 shown
in FIGS. 5 (a) and 5 (b), it is shown in FIG. As such, it is confirmed that there is no difference in
their frequency response.
[0059]
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16
This will be described specifically.
The microphone device 5 provided with the microphones 7 and 8 shown in FIG. 2 is set at the
front position of the proximity sound source 9, and the distance between the proximity sound
source 9 and the first microphone 7 is set to L. In this case, the second microphone 8 is disposed
farther from the proximity sound source 9 than the first microphone 7. In this state, a signal was
outputted from the proximity sound source 9 while changing the frequency in the range of 20 Hz
to 20 KHz, and the frequency responsiveness of the microphones 7 and 8 to the signal was
evaluated. The evaluation result is shown as Case 1 by a dashed-dotted line in FIG.
[0060]
Further, the microphone device 5 provided with the microphones 7 and 8 shown in FIG. 3 is set
at the front position of the proximity sound source 9. In this case, the second microphone 8 is
disposed laterally to the first microphone 7 and sets the distance between the proximity sound
source 9 and the first microphones 7 and 8 to L, respectively. In this state, from the proximity
sound source 9, the pseudo sound was outputted while changing the frequency in the range of
20 Hz to 20 KHz, and the frequency response when the pseudo sound was reproduced by the
microphones 7 and 8 was evaluated. The evaluation result is shown as Case 2 by a solid line in
FIG.
[0061]
As is clear from the evaluation results shown in FIG. 5 (c), a configuration in which the first
microphone 7 and the second microphone 8 are arranged in a straight line as shown in FIG. 2
and a second one as shown in FIG. In the case of the configuration in which the microphones 8
are arranged to be laterally displaced with respect to the first microphones 7, their respective
frequency responses are similar. Therefore, it is understood that the arrangement relationship of
the first microphone 7 and the second microphone 8 may be selected to any arrangement
relationship shown in FIG. 2 or FIG. 3 depending on the object to which the microphone device 5
is applied. . Furthermore, also in that case, the frequency response does not change.
[0062]
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Next, the structure in the case of attaching the microphone apparatus 5 which concerns on
embodiment of this invention to a headset is demonstrated. The microphone attachment
structure shown in FIG. 4 corresponds to FIG.
[0063]
As shown in FIG. 4, a substantially S-shaped piece 11 is attached to the tip of the arm 4 of the
headset. Flat pieces 11 a and 11 b having an angle θ with the axis of the arm 4 are formed on
the piece 1 back to back. Of the flat surfaces 11a and 11b of the piece 1, the flat surface 11a on
the tip side is the mouth of the speaker 1 as shown by the arrows when the speaker 1 wears the
headset as shown in FIGS. It is formed to face the 1a side. Further, the flat surface 11b on the
front side is formed toward the outside on the opposite side to the mouth 1a of the speaker 1.
[0064]
The first microphone 7 is incorporated in the piece 11, and the pressure receiving portion of the
first microphone 7 is opened in the flat surface 11a. Therefore, the first microphone 7 mainly
receives the sound pressure of the voice from the speaker 1 at the pressure receiving unit, and
outputs a voltage signal as sound information.
[0065]
The second microphone 8 is incorporated in the piece 11, and the pressure receiving portion of
the second microphone 8 is opened in the flat surface 11b. Therefore, since the second
microphone 8 is set to be directed outward with respect to the mouth 1 a of the speaker 1, the
second microphone 8 is a far-field sound field in addition to the voice from the speaker 1. The
pressure receiving unit receives sound pressure due to noise or the like generated from the noise
source 6 and outputs a voltage signal as sound information.
[0066]
According to the microphone attachment structure shown in FIG. 4, when the speaker 1 wears a
headset, only the first microphone 7 is set at the mouth 1a of the speaker 1, and the second
microphone 8 The speaker 7 is set apart from the microphone 7 and is set on the arm 4 side, so
that the speaker does not feel uncomfortable.
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[0067]
Next, the result of evaluating the characteristics of the microphone device 5 according to the
embodiment of the present invention will be described.
This evaluation was performed to evaluate the difference from the frequency response of the
conventional close talk type microphone shown in FIG.
[0068]
The said evaluation was performed as follows. That is, as shown to Fig.7 (a), the pseudo |
simulation proximity sound source 9 was prepared. Further, as the microphone device 5, the
microphone device 5 shown in FIG. 2 was used. The microphone device 5 was set at the front
position of the proximity sound source 9 and the distance between the proximity sound source 9
and the first microphone 7 was set to L. In this case, the second microphone 8 is disposed farther
from the proximity sound source 9 than the first microphone 7. In this state, the frequency of the
signal from the proximity sound source 9 was changed in the range of 20 Hz to 20 KHz, and the
frequency response was output.
[0069]
Furthermore, the distance between the central position between the first microphone 7 and the
second microphone 8 and the proximity sound source 9 was changed to L1 and L2. When the
distance is L1, it means that the first microphone 7 and the second microphone 8 of the
microphone device 5 according to the embodiment of the present invention are set in the
spherical sound field generated by the proximity sound source 9 . When the distance is L2, the
first microphone 7 and the second microphone 8 of the microphone device 5 according to the
embodiment of the present invention are generated by the noise source 6 located far from the
proximity sound source 9 It means being set in the far field. The distance L1 was set to 2.5 cm,
and the distance L2 was set to 1 m.
[0070]
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In FIG. 7B, when the distance between the center position between the first microphone 7 and
the second microphone 8 and the proximity sound source 9 is set to L2, as shown by a solid line,
The response is extremely degraded, showing characteristics that are gradually improved as the
frequency is shifted to the high frequency range. Furthermore, large peaks and dips occur in the
region exceeding 8 KHZ. It can be understood that such frequency response is inadequate as a
microphone device that requires flat frequency response to a close proximity sound source.
[0071]
In FIG. 7B, when the distance between the center position between the first microphone 7 and
the second microphone 8 and the proximity sound source 9 is set to L1, that is, the first
microphone 7 and the second microphone When the microphone 8 is set in the spherical sound
field generated by the proximity sound source 9, it can be seen that the frequency response is
flat over the low frequency range to the high frequency range, as indicated by the alternate long
and short dash line. Also, it can be seen that the damping phenomenon in the high frequency
range is also suppressed to a very small extent.
[0072]
Furthermore, in the microphone device 5 according to the embodiment of the present invention,
the following should be noted. That is, the noise suppression effect in the low frequency range is
extremely large, and the output level in the frequency response is significantly improved to
around 18 dB. Moreover, the output level of about 18 dB is maintained from the low frequency
range to the high frequency range, as is apparent from FIG. 7 (b). Furthermore, the upper limit of
the high frequency range is extended to about 20 KHz, and the frequency response is flat even in
the vicinity thereof, and the output level is also significantly improved.
[0073]
According to the evaluation result shown in FIG. 7B, in the embodiment of the present invention,
the first microphone 7 and the second microphone 8 which form a pair are disposed in the
spherical acoustic field generated by the proximity sound source 9, and 1. Based on a
configuration in which one microphone 7 is set at a position approaching the proximity sound
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source 9 and the second microphone 8 is set at a distance relative to the distance between the
microphone 7 and the proximity sound source 9 It is believed that there is. Further, the distance
d between the acoustic terminals between the first microphone 7 and the second microphone 8
is determined based on the upper limit value of the frequency range in which noise can be
generated by the sound pressure of the plane wave, and the evaluation result is shown in FIG.
Because of the result shown in b), it has been proved that the distance d between the acoustic
terminals between the first microphone 7 and the second microphone 8 is relatively wide.
[0074]
As described above, according to the embodiment of the invention of sound, it is possible to
obtain flat response characteristics with respect to the proximity sound source, and to
sufficiently secure the noise suppression effect in the low frequency range. Furthermore, since
the noise suppression effect can be obtained only by subtracting the output signals from the first
microphone and the second microphone, it is possible to miniaturize without requiring an extra
circuit other than the microphone.
[0075]
In the embodiment of the present invention, although the case where the present invention is
applied to the microphone device of the headset used in the call center has been described, the
present invention is not limited thereto. The present invention can be applied not only to a call
center but also to voice communication under a noise environment, such as a microphone device
used in, for example, a store / game hall, an office, a factory or an outdoor work place.
[0076]
Further, in the embodiment of the present invention, although non-directional microphones are
used for the first microphone and the second microphone, those microphones having directivity
are used as these microphones, and the frequency response etc. is corrected by the circuit
configuration. It may be done.
[0077]
In the above description, although the case where ambient noise suppression is turned on is
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21
described, the present invention is not limited to this.
The first microphone near the sound source as shown in FIG. 8, for example, when it is desired to
convey the surrounding atmosphere to the other party, or when the wind is very strong and the
wind noise level is high and conversation using the microphone device is difficult. The operation
of the microphone 8 may be switched off by the switch 12 so that only the sound picked up at 7
is output and the output of the second microphone 8 is not supplied to the subtractor 10.
[0078]
Next, an embodiment in which the microphone device according to the present invention is
incorporated into a portable terminal will be described. In this embodiment, the microphone
device according to the present invention is incorporated in a mobile phone which is one of
mobile terminals. The mobile terminal is not limited to the mobile phone, and the microphone
device according to the present invention may be incorporated in a mobile terminal other than
the mobile phone.
[0079]
The mobile phone 13 shown in FIG. 9 is used when the user needs to carry it, and when used in
crowds of people, etc., the microphone of the mobile phone 13 picks up surrounding voices etc.
The voice of the other party is difficult to hear.
[0080]
Therefore, in the embodiment of the present invention, the microphone of the mobile phone 13 is
used as the first microphone 7, the second microphone 8 is attached to the arm 14, and the arm
14 is attached to the mobile phone 13 so as to be able to extend.
[0081]
When the mobile phone 13 shown in FIG. 9 is used, the voice emitted by the user is a close
proximity sound source.
As shown in FIG. 10A, the arm 14 is drawn out linearly along a slide groove (not shown) formed
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on the mobile phone 13 as shown in FIG. 10A. As shown in (b), one end of the arm 14 is pivotally
supported and rotatably attached, and the arm 14 is rotated so that the second microphone 8 is
extended to the outside of the mobile phone 13.
[0082]
As shown in FIG. 10A or FIG. 10B, when the second microphone 8 is pulled out of the mobile
phone 13 and set when the mobile phone 13 is used, the second microphone 8 is a first
microphone. The distance between the first microphone 7 and the second microphone 8 is set to
the distance d between the acoustic terminals described above.
[0083]
According to the embodiment of the present invention shown in FIGS. 10 (a) and 10 (b), as
described above, the first microphone 7 and the second microphone 8 forming the pair are close
proximity sound sources (user's voice). Since it is arranged in the spherical wave field generated
by the above, it is not necessary to estimate the transfer coefficient of the path through which
noise passes, which has to be taken into consideration in the case of the microphone device
shown in FIG. It becomes unnecessary and the structure of the microphone device can be
simplified.
Furthermore, the noise suppression effect can be obtained only by subtracting the sound
information output from the first microphone 7 and the second microphone 8.
[0084]
Furthermore, by setting the first microphone 7 at a position approaching the proximity sound
source, and setting the second microphone 8 at a distance relative to the distance between the
microphone 7 and the proximity sound source, It is possible to ensure a relatively wide distance
d between the acoustic terminals, which is the distance between the first microphone 7 and the
second microphone 8, and the frequency response of the microphone device to the proximity
sound source is improved.
[0085]
In the embodiment shown in FIGS. 10 (a) and 10 (b), the second microphone 8 is shown in FIG. 8
with the arm 14 attached with the second microphone 8 folded in the mobile phone 13. The
second microphone 8 may be connected to the circuit by the switch 12 when the switch 12 is
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23
separated from the circuit and the arm 14 is pulled out to set the second microphone 8 in a fixed
position. It is.
[0086]
In the embodiment shown in FIG. 9 and FIG. 10, the arm 14 having the second microphone 8
attached thereto is attached to the mobile phone 13 so as to be able to be pulled out to the
outside, but it is not limited thereto.
When the arm 24 attached with the second microphone 8 is detachably attached to the mobile
phone 13 and the second microphone 8 is used, the arm 24 is attached to the mobile phone 13
and the second microphone 8 is It may be set to be distant from the distance between the
microphone 7 and the proximity sound source.
[0087]
Further, as shown in FIG. 11, the first microphone 7 is fixed to the mobile phone 13 at a position
where it picks up the voice of the user who is the proximity sound source, and the second
microphone 8 is the first microphone 7 and the proximity sound source. , And may be fixed to
the mobile phone 13 by setting it at a distance as compared with the distance between them.
Also in this case, when the second microphone 8 is not used, the second microphone 8 is
disconnected from the circuit by the switch 12 as shown in FIG. 8, and conversely, when the
second microphone 8 is used, The two microphones 8 may be connected to the circuit by the
switch 12.
Also in this case, the distance between the first microphone 7 and the second microphone 8 is set
to the above-described distance d between acoustic terminals.
[0088]
In the case of the embodiment shown in FIG. 11, when the user grips the mobile phone 13, the
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24
openings of the first microphone 7 and the second microphone 8 may be covered by the user's
hand. Therefore, as shown in FIG. 11, one end of the first sound conductor 15 for guiding the
sound from the proximity sound source is connected to the first microphone 7, and the other end
of the sound conductor 15 is not blocked by the user's hand. Open in position. Similarly, one end
of the second sound conductor 16 is connected to the second microphone 8 and the other end of
the sound conductor 15 is opened at a position where it is not blocked by the user's hand.
[0089]
According to the embodiment shown in FIG. 11, since the first microphone 7 and the second
microphone 8 are incorporated in the mobile phone 13 and these microphones 7 and 8 do not
protrude outside the mobile phone 13, a general-purpose mobile phone It can be used without
discomfort. Also, the first microphone 7 and the second microphone 8 can reliably pick up sound
information due to the presence of the sound conductors 15 and 16, and the noise suppression
effect by the first microphone 7 and the second microphone 8 is sufficiently Can be
[0090]
As described above, according to the present invention, it is suitable as a microphone device used
not only in a call center but also in voice communication under a noise environment, such as a
store / game hall, an office, a factory / outdoor work place.
[0091]
FIG. 1 illustrates an example environment in which a microphone device according to an
embodiment of the present invention may be used.
It is a figure which shows the arrangement | positioning relationship of the microphone in
embodiment of this invention. It is a figure which shows the arrangement | positioning
relationship of the microphone in embodiment of this invention. It is a figure which shows the
attachment state of the microphone in embodiment of this invention, Comprising: (a) is a top
view, (b) is the figure seen from the front side, (c) is the figure seen from the speaker side. (A)
And (b) is a figure which shows the arrangement | positioning relationship for evaluating the
difference in the characteristic of the microphone apparatus shown to FIG.2 and FIG.3, (c) is a
characteristic view which shows an evaluation result. (A) is a circuit diagram showing a case
where a subtraction process is performed on signals output from the first microphone and the
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second microphone, (b) and (c) are output by the first and second microphones It is a wave form
diagram showing an example of a signal. (A) is a figure which shows the state which evaluates
the microphone apparatus based on embodiment of this invention, (b) is a characteristic view
which shows an evaluation result. FIG. 7 is a circuit diagram showing a microphone device
according to another embodiment of the present invention. It is an embodiment which
incorporated the microphone device concerning the present invention into a mobile telephone,
and is a front view showing the state where a microphone device was folded up. (A) is an
embodiment in which the microphone device according to the present invention is incorporated
in a mobile phone, and is a front view showing a configuration in which the arm is extended
linearly and the second microphone is drawn out of the mobile phone; FIG. 10 is a front view
showing a configuration for rotating the arm and pulling out the second microphone to the
outside of the mobile phone. (A) is a front view showing another embodiment in which the
microphone device according to the present invention is incorporated in a mobile phone, and (b)
is a side view showing the same. It is a characteristic view showing the relation between the
distance between sound terminals which is the interval of the 1st microphone and the 2nd
microphone, and the amount of noise suppression. FIG. 1 shows a microphone device
incorporated in a conventional headset. It is sectional drawing which shows the conventional
close talk type microphone. It is a characteristic view which shows the frequency response by the
close talk type microphone shown in FIG. It is a figure which shows the conventional microphone
apparatus. It is a figure which shows the conventional microphone apparatus.
Explanation of sign
[0092]
5 Microphone device 6 Noise source (far-distance source) 7 First microphone 8 Second
microphone 9 Proximity source 12 Switch
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