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JP2014155145

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DESCRIPTION JP2014155145
Abstract: To provide an earphone microphone that can be miniaturized and has an inexpensive
echo suppression function. An earphone microphone includes one speaker, a differential
microphone, and a main body case. The differential microphone has first and second sound
collection holes. The main body case is formed with first and second openings communicating
with the outside, a first acoustic space communicating with the first opening, and a second
acoustic space communicating with the second opening. The sound input to the first sound
collection hole propagates in the first sound space. In the second acoustic space, a speaker is
disposed, and sound input to the second sound collection hole propagates. The second acoustic
space functions as a Helmholtz resonator for sound propagating through the second opening.
[Selected figure] Figure 3
イヤホンマイク
[0001]
The present invention relates to an earphone microphone, and more particularly to an earphone
microphone equipped with a speaker and a microphone.
[0002]
Conventionally, an earphone microphone incorporating a speaker and a microphone is known.
The user can transmit the user's voice input to the microphone while listening to the voice such
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as the speaking voice output from the speaker through the earphone microphone worn on the
ear. Therefore, it is used for hands-free communication of mobile phones and the like.
[0003]
However, the voice of the speaker emitted in the ear canal of the user is reflected in the user's
eardrum and in the ear canal, etc., and is input to the earphone microphone as noise (echo
component). Therefore, the microphone built in the earphone microphone picks up the echo
component of the sound outputted from the speaker in addition to the user's sound. Therefore,
there is a problem that the echo component is mixed as noise with the voice transmitted from the
earphone microphone.
[0004]
Therefore, for example, as in Patent Document 1, an earphone microphone having an echo
cancellation function is known. The earphone microphone of Patent Document 1 incorporates
two speakers and a microphone. One speaker outputs a voice such as a speaking voice, and the
other speaker outputs a voice for canceling an echo component of the voice output from the one
speaker. The echo component of the sound output from one of the speakers and the sound of the
other speaker are input to the microphone, and the echo component is suppressed by canceling
out each other.
[0005]
Unexamined-Japanese-Patent No. 2007-201887
[0006]
However, since the earphone microphone of Patent Document 1 incorporates a plurality of
speakers in the main body case, the space for mounting the speakers and the sound path thereof
increases inside the main body case.
Therefore, there is a problem that it is difficult to miniaturize the main body case. In addition,
there is also a problem that it is relatively expensive because of the high manufacturing cost.
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[0007]
The present invention has been made in view of such circumstances, and it is an object of the
present invention to provide an earphone microphone that can be miniaturized and has an
inexpensive echo suppression function.
[0008]
In order to achieve the above object, an earphone microphone according to one aspect of the
present invention includes a single speaker, a differential microphone having first and second
sound collection holes, and a main body housing, and A first acoustic space communicating with
the first opening, a first acoustic space communicating with the first opening, and a second
acoustic space communicating with the second opening are formed in the first acoustic space.
The sound input to the first sound collection hole propagates, and the speaker is arranged in the
second acoustic space, and the sound input to the second sound collection hole propagates, and
the second acoustic space It functions as a Helmholtz resonator for sound propagating through
the two openings.
[0009]
According to the above configuration, the earphone microphone has one speaker.
Further, the first and second acoustic spaces communicate with the outside of the main body
housing through the first and second openings, respectively.
In addition, a speaker is disposed in the second acoustic space. Further, the second acoustic
space functions as a Helmholtz resonator for the sound propagating through the second opening.
Therefore, the input voice from the external sound source resonates in the second acoustic space
and is then input to the second sound collection hole. At this time, in the frequency band near the
resonance frequency in the second acoustic space, a difference occurs in the sound pressure of
the input sound input to the first and second sound collection holes. Therefore, the input voices
input to the first and second sound collection holes are collected by the differential microphone
without canceling each other. Further, the output sound of the speaker is input to the first sound
collection hole via the second acoustic space, the second opening, the outside of the main body
casing, the first opening, and the first acoustic space. Also, the output sound is directly input to
the second sound collection hole in the second acoustic space. Then, the output sound input to
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the first and second sound collection holes weakens each other, whereby the sound collection of
the output sound is suppressed. Therefore, the earphone microphone can realize the echo
suppression function of the output sound of the speaker without requiring a plurality of
speakers. Furthermore, the earphone microphone can transmit input voice while suppressing
noise derived from the output voice of the speaker. Therefore, it is possible to provide an
earphone microphone that can be miniaturized and has an inexpensive echo suppression
function.
[0010]
Further, in the above configuration, the first acoustic space may function as a Helmholtz
resonator for voice propagating through the first opening, and the volume of the second acoustic
space may be larger than that of the first acoustic space. .
[0011]
According to this configuration, the sound propagating from the outside of the main body case to
the first and second acoustic spaces via the first and second openings resonates due to the
Helmholtz resonance.
Furthermore, the volume of the second acoustic space is larger than the volume of the first
acoustic space. Therefore, due to the volume ratio of the first and second acoustic spaces, the
resonant frequency of the first acoustic space appears in a frequency band higher than the
resonant frequency of the second acoustic space. Therefore, in the frequency band including the
resonance frequency of the second acoustic space, the input sound from the external sound
source input to the first and second sound collection holes can be prevented from canceling each
other. Since the speaker is disposed in the second acoustic space, the output sound of the
speaker input to the second sound collection hole does not resonate. Therefore, in the abovementioned frequency band, the output sounds of the speakers input to the first and second sound
collection holes can be mutually attenuated. Therefore, the earphone microphone can transmit
the input voice from the external sound source input to the differential microphone while
suppressing the noise derived from the output voice of the speaker.
[0012]
Furthermore, in the above configuration, the volume ratio of the first and second acoustic spaces
is such that the sound propagating to the first acoustic space via the first opening does not
resonate at least within a predetermined frequency band, and the second opening The sound
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propagating to the second acoustic space via V.sub.2 may be set to resonate within a
predetermined frequency band.
[0013]
According to this configuration, it is possible to prevent input voices from external sound sources
input to the first and second sound collection holes from being canceled each other in a
predetermined frequency range.
Furthermore, the output sounds of the speakers input to the first and second sound collection
holes can be mutually attenuated. Therefore, the earphone microphone can realize an echo
suppression function in a predetermined frequency region such as a working frequency band of a
differential microphone, for example.
[0014]
In the above configuration, the volume ratio of the second acoustic space to the first acoustic
space may be 5 or more and 800 or less.
[0015]
According to this configuration, for the sound propagating to the first and second acoustic spaces
via the first and second openings, the resonant frequency in the first acoustic space is different
from the resonant frequency in the second acoustic space It can be much larger than that.
Therefore, the earphone microphone can reliably realize the echo suppression function.
[0016]
In the above configuration, the resonance frequency of the sound propagating to the first
acoustic space via the first opening is 4 kHz or more, and the resonance frequency of the sound
propagating to the second acoustic space via the second opening May be 1 kHz or more and 2
kHz or less.
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[0017]
According to this configuration, the resonance frequency of the sound propagating to the first
acoustic space via the first opening can be outside the use frequency band (for example, 300 Hz
to 3.4 Hz) of the differential microphone.
Furthermore, the resonance frequency of the sound propagating to the second acoustic space via
the second opening can be made within the working frequency band of the differential
microphone. Therefore, in the working frequency band of the differential microphone, the
earphone microphone can transmit the input voice from the external sound source input to the
differential microphone while suppressing the noise derived from the output voice of the
speaker.
[0018]
According to the present invention, it is possible to provide an earphone microphone that can be
miniaturized and has an inexpensive echo suppression function.
[0019]
It is an external appearance perspective view of an earphone microphone.
It is a figure which shows the state with which the earphone microphone was mounted ¦ worn
with the user's external ear canal. It is sectional drawing of a main-body part. It is a front view of
a main part seen from the user's ear canal side. It is a side view of a main part. It is a front view
showing other examples of formation of the 1st and 2nd opening. It is a front view showing other
examples of formation of the 1st and 2nd opening. It is a front view showing other examples of
formation of the 1st and 2nd opening. It is a front view showing other examples of formation of
the 1st and 2nd opening. It is a principle view of a Helmholtz resonator. It is a conceptual block
diagram for demonstrating the principle of the mechanism which suppresses an echo
component. It is a sound collection block diagram of an output voice. It is a graph for
demonstrating the principle of the mechanism which suppresses an echo component. It is a
conceptual block diagram for demonstrating the principle of the mechanism in which a
microphone collects an input audio ¦ voice. It is a sound collection block diagram of input speech.
It is a graph for demonstrating the principle of the mechanism in which a microphone collects an
input audio ¦ voice. It is a graph which shows an example of the sensitivity characteristic of the
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microphone in this embodiment.
[0020]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings. <Configuration of earphone microphone>
[0021]
FIG. 1 is an external perspective view of an earphone microphone. The earphone microphone 1 is
a sound collection device connected to an electronic device (not shown) such as a mobile phone,
for example. As shown in FIG. 1, the earphone microphone 1 includes a main body 2, a cable 4,
and a connector 5.
[0022]
The main unit 2 is attached to the user's ear, emits an output sound, and collects an input sound
from an external sound source (e.g., a user's speaking voice). The specific configuration of the
main body 2 will be described in detail later. The cable 4 is a signal line which is connected
between the main body 2 and the connector 5 and transmits / receives a signal between the
electronic device (not shown) to which the earphone microphone 1 is connected and the main
body 2 via the connector 5 is there. The connector 5 is an input / output terminal connected to
an interface of an electronic device (not shown).
[0023]
FIG. 2 is a view showing a state in which the earphone microphone is attached to the user's ear
canal. As shown in FIG. 2, the earphone microphone 1 is attached to the ear EAR of the user, and
emits the sound based on the audio signal output from the electronic device (not shown) toward
the eardrum E1 of the user. Further, not only the voice uttered by the user is emitted from the
mouth, but a part of the voice is transmitted from the tympanic membrane E1 to the ear canal E2
through the skull and the muscles of the face. The earphone microphone 1 picks up a voice such
as the user's voice (i.e., an input voice from an external sound source), and further generates a
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voice signal based on the collected voice and outputs it to an electronic device (not shown) Do.
The electronic device to which the earphone microphone 1 is connected is not particularly
limited.
[0024]
Here, the output sound emitted from the earphone microphone 1 into the ear canal E2 of the
user is reflected by the user's eardrum E1, the ear canal E2, etc., and is input to the earphone
microphone 1 as noise. Below, this noise is called an echo component. The earphone microphone
1 has an echo suppression function for suppressing noise derived from such an echo component
as described later. Therefore, the earphone microphone 1 can collect clear sound in which noise
(in particular, an echo component of output sound) is suppressed.
[0025]
Next, the configuration of the main unit 2 will be described in detail. FIG. 3 is a cross-sectional
view of the main body. FIG. 4 is a front view of the main body seen from the side of the user's ear
canal. FIG. 5 is a side view of the main body. In addition, FIG. 3 has shown the cross-section of the
main-body part 2 in alignment with dashed-dotted line AA of FIG.
[0026]
As shown in FIG. 3, the main body unit 2 is configured to include a speaker 21, a microphone 22,
a main body case 23, and an ear pad 25.
[0027]
The speaker 21 is an audio output unit having a sound emission hole 21 a for outputting an
output sound.
The speaker 21 is electrically connected to the cable 4 and outputs an output sound based on an
audio signal transmitted from an electronic device (not shown) via the cable 4 and the connector
5. Although the sound release holes 21a of the speaker 21 are directed in a direction
substantially perpendicular to the longitudinal direction of the main body case 23 in FIG. 3, the
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direction of the speaker 21 is not limited to the example of FIG. The orientation of the speaker 21
may be, for example, a direction substantially parallel to the longitudinal direction of the main
body casing 23.
[0028]
The microphone 22 is a differential microphone having first and second sound collection holes
221 a and 221 b arranged side by side in the longitudinal direction of the main body case 23,
and is electrically connected to the cable 4. Although the microphone 22 is not particularly
limited, for example, a MEMS microphone, an ECM microphone, or the like can be used. The
microphone 22 generates a first sound signal based on the sound input to the first sound
collection hole 221a, and generates a second sound signal based on the sound input to the
second sound collection hole 221b. Further, the microphone 22 generates a differential sound
signal based on the difference between the sound pressure of the sound input to the first sound
collection hole 221 a and the sound pressure of the sound input to the second sound collection
hole 221 b. The microphone 22 outputs these signals to an electronic device (not shown) via the
cable 4 and the connector 5.
[0029]
One speaker 21 and a microphone 22 are mounted on the main body case 23. Further, as shown
in FIGS. 3 to 5, an insertion portion 23 a is formed in the main body case 23. In the insertion
portion 23a, as shown in FIG. 4, voice is input to the earphone microphone 1 on the surface
facing the eardrum E1 of the user when the main body 2 is attached to the user's ear EAR as
shown in FIG. First and second openings 231a and 231b for output are formed concentrically.
[0030]
The shapes of the first and second openings 231a and 231b formed in the insertion portion 23a
are not particularly limited. 6A to 6D are front views showing another example of forming the
second and third openings. The first and second openings 231a and 231b may be, for example,
two openings separated by a predetermined distance as shown in FIGS. 6A to 6D. In addition, the
shapes of the first and second openings 231a and 231b are, for example, polygonal shapes such
as semicircular (see FIG. 6A), circular (see FIG. 6B), square (see FIG. 6C), and triangle (see FIG.
6D). It may be The shapes and sizes of the first and second openings 231a and 231b may be
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substantially the same or different.
[0031]
Further, as shown in FIG. 3, first and second sound spaces 232 a and 232 b are formed inside the
main body case 23.
[0032]
The first acoustic space 232a communicates with the first sound collecting hole 221a and the
first opening 231a, and is an acoustic space through which the sound input to the first sound
collecting hole 221a propagates.
Audio is transmitted to the first acoustic space 232a from the outside of the main body casing 23
via the first opening 231a. This voice is, for example, an echo component of the output voice of
the speaker 21, an input voice from an external sound source (for example, a user's speaking
voice propagating through the eardrum E1 and the ear canal E2). The first acoustic space 232a
guides these voices to the first sound collecting hole 221a.
[0033]
The second acoustic space 232 b communicates with the second sound collection hole 221 b and
the second opening 231 b, and is an acoustic space in which the sound input to the second sound
collection hole 221 b propagates. The speaker 21 is disposed in the second acoustic space 232 b.
Therefore, the output sound of the speaker 21 propagates to the outside of the main housing 23
via the second acoustic space 232 b and the second opening 231 b and is directly input to the
second sound collection hole 221 b.
[0034]
In addition, the first and second acoustic spaces 232a and 232b function as Helmholtz
resonators 7 for voices propagating through the first and second openings 221a and 221b. Here,
the Helmholtz resonator 7 will be briefly described. FIG. 7 is a principle diagram of a Helmholtz
resonator. The Helmholtz resonator 7 is configured of a container 71 of volume V in which the
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opening 71a of the cross-sectional area S is formed, and a tubular neck portion 72 of length L
communicating with the opening 71a. When sound is propagated from the outside to the inside
of the container 71 via the neck portion 72 and the opening 71a, the sound resonates at the
Helmholtz resonance frequency f. The Helmholtz resonance frequency f is given by the following
Equation 1. f = (C / 2π) * {S / (L * V)} <1/2> (Equation 1) In Equation 1, C represents the velocity
of sound.
[0035]
As shown in Equation 1, the Helmholtz resonance frequency f is proportional to the square root
of the cross-sectional area S of the neck 72 and inversely proportional to the square root of the
path length L of the neck 72. In particular, the Helmholtz resonance frequency f is inversely
proportional to the square root of the volume V of the container 71. Therefore, the Helmholtz
resonance frequency f appears in a higher frequency band as the volume V of the container 71 is
smaller. In the present embodiment, the cross-sectional areas S1 and S2 of the first and second
openings 231a and 231b as viewed in the longitudinal direction of the main housing 23
correspond to the cross-sectional area S of the opening 71a of the Helmholtz resonator 7.
Further, the path lengths L1 and L2 of the first and second openings 231a and 231b in the
longitudinal direction of the main body casing 23 correspond to the path length L of the neck
portion 72 of the Helmholtz resonator 7. Further, the volumes V 1 and V 2 of the first and
second acoustic spaces 232 a and 232 b correspond to the volume V of the container 71 of the
Helmholtz resonator 7. Therefore, the sound propagating from the outside of the main body case
23 to the first and second acoustic spaces 232a and 232b via the first and second openings 231a
and 231b has the Helmholtz resonance frequency f1 given by the above-mentioned Equation 1. ,
Resonates at f2.
[0036]
In the present embodiment, the cross-sectional area S1 of the first opening 231a with which the
first acoustic space 232a communicates is, for example, 0.7 to 3.2 (mm <2>), and the first in the
longitudinal direction of the main housing 23 The path length L1 of the opening 231a is, for
example, 0.2 to 2.0 (mm). The volume V1 of the first acoustic space 232a is, for example, 3.5 to
60 (mm <3>). Therefore, the Helmholtz resonance frequency f1 of the sound propagating from
the outside of the main body casing 23 to the first acoustic space 232a via the first opening
231a is approximately 4 kHz or higher, and the frequency band generally used by the
microphone 22 ( For example, 300 Hz to 3.4 kHz).
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[0037]
Further, in the present embodiment, the cross-sectional area S2 of the second opening 231b
communicating with the second acoustic space 232b is, for example, 0.7 to 12 (mm <2>). The
path length L2 of the opening 231b is, for example, 0.2 to 4.0 (mm). The volume V2 of the
second acoustic space 232b is, for example, 300 to 2400 (mm <3>). Therefore, the Helmholtz
resonance frequency f2 of the sound propagating from the outside of the main body casing 23 to
the second acoustic space 232b via the second opening 231b appears in the frequency band
generally used by the microphone 22.
[0038]
The volume ratio (V2 / V1) of the first and second acoustic spaces 232a and 232b can take
numerical values in the range derived from the above-mentioned respective volumes V1 and V2,
but in fact, it is 5.0 to 800 It is desirable to be in the range.
[0039]
Thus, in the present embodiment, the volume V1 of the first acoustic space 232a is smaller than
the volume V2 of the second acoustic space 232b.
Therefore, the Helmholtz resonance frequency f1 in the first acoustic space 232a appears in a
frequency band higher than the Helmholtz resonance frequency f2 in the second acoustic space
232b.
[0040]
The ear pad 25 is formed of, for example, a resin material, and is covered on the insertion portion
23 a. When the main body 2 is attached to the ear EAR of the user (see FIG. 2), the ear pad 25 is
inserted into the ear canal E2 of the user together with the insertion portion 23a. At this time, the
ear pad 25 seals the gap between the insertion portion 23a and the opening of the user's
external ear canal E2 substantially without a gap. Therefore, it is possible to substantially block
external sound that enters from between the insertion portion 23a and the opening of the ear
canal E2. <Echo suppression function of earphone microphone>
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[0041]
Next, regarding the echo suppression function of the earphone microphone 1, the case where the
output sound of the speaker 21 is collected by the microphone 22 and the case where the input
sound from an external sound source (for example, the user's speaking voice etc.) is collected by
the microphone 22 We divide into and, and explain. << When the output sound of the speaker is
collected by the microphone >>
[0042]
First, the case where the output sound of the speaker 21 is collected by the microphone 22 will
be described. FIG. 8 is a conceptual block diagram for explaining the principle of a mechanism
for suppressing an echo component. Further, FIG. 9 is a sound collection block diagram of the
output sound. FIG. 10 is a graph for explaining the principle of the mechanism for suppressing
an echo component. The solid line Ca in FIG. 10 is a characteristic curve showing the frequency
characteristic of the sensitivity of the microphone 22 to the sound input to the first sound
collection hole 221a. Further, a broken line Cb in FIG. 10 is a characteristic curve indicating the
frequency characteristic of the sensitivity of the microphone 22 to the sound input to the second
sound collection hole 221a. In FIG. 10, characteristic curves Ca and Cb in an ideal state are
shown in order to facilitate understanding of the principle of the mechanism for suppressing an
echo component.
[0043]
As shown in FIGS. 8 and 9, the output sound of the sound pressure P1 output from the speaker
21 is emitted from the speaker 21 to the ear canal E2 via the second acoustic space 232b and
the second opening 231b. The emitted output sound is echoed by the user's eardrum E1 and the
inner wall of the ear canal E2. The echoed output sound propagates as an echo component to the
first acoustic space 232a via the first opening 231a, and is input to the first sound collection hole
221a.
[0044]
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At this time, the sensitivity of the microphone 22 becomes high in the frequency band near the
Helmholtz resonance frequency f1 of the echo component propagating to the first acoustic space
232a due to the Helmholtz resonance phenomenon. However, the volume of the first acoustic
space 232a is minute as described above. Therefore, the Helmholtz resonance frequency f1
appears in a frequency band higher than a working frequency band (for example, 300 Hz to 3.4
kHz) at which the microphone 22 collects sound, as indicated by the characteristic curve Ca in
FIG. Therefore, the sensitivity of the microphone 22 is high in a frequency band higher than the
working frequency band, but substantially flat in the working frequency band.
[0045]
On the other hand, as shown in FIGS. 8 and 9, the output sound of the speaker 21 is input from
the speaker 21 directly to the second sound hole 221b in the second acoustic space 232b.
Therefore, the output sound input to the second sound collection hole 221b is not affected by the
Helmholtz resonance phenomenon. Therefore, as shown by the characteristic curve Cb in FIG. 10,
the sensitivity of the microphone 22 is flat without becoming high in all frequency bands
including the used frequency band.
[0046]
Therefore, in the working frequency band of the microphone 22, the voices input to the first and
second sound collection holes 221a and 221b weaken each other, thereby suppressing the echo
component of the output voice of the speaker 21 input to the microphone 22. be able to. <<
When the input sound from the external sound source is collected by the microphone >>
[0047]
Next, a case where an input voice (for example, a user's speech) from an external sound source is
collected by the microphone 22 will be described. FIG. 11 is a conceptual block diagram for
explaining the principle of a mechanism by which a microphone collects an input voice. FIG. 12 is
a block diagram of sound collection of input speech. Further, FIG. 13 is a graph for explaining the
principle of the mechanism in which the microphone collects the input voice. In FIG. 13, a
characteristic curve Ca indicating the frequency characteristic of the sensitivity of the
microphone 22 to the sound input to the first sound collection hole 221 a is indicated by a solid
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line. Further, a characteristic curve Cb indicating the frequency characteristic of the sensitivity of
the microphone 22 to the sound input to the second sound collection hole 221b is indicated by a
broken line. Note that FIG. 13 shows characteristic curves Ca and Cb in an ideal state in order to
facilitate understanding of the principle of the mechanism by which the microphone 22 collects
the input voice.
[0048]
As shown in FIGS. 11 and 12, when the earphone microphone 1 is attached to the user's external
ear canal E2 as shown in FIG. 2, the input sound of the sound pressure P2 passes from the
eardrum E1 and the external ear canal E2 via the first opening 231a. And propagates to the first
acoustic space 232a and is input to the first sound collection hole 221a.
[0049]
At this time, the sensitivity of the microphone 22 becomes high in the frequency band near the
Helmholtz resonance frequency f1 of the input sound propagating to the first acoustic space
232a due to the Helmholtz resonance phenomenon.
However, the volume of the first acoustic space 232a is minute as described above. Therefore,
the Helmholtz resonance frequency f1 appears in a frequency band higher than the working
frequency band in which the microphone 22 collects sound, as indicated by the characteristic
curve Ca in FIG. Therefore, the sensitivity of the microphone 22 is high outside the use frequency
band, but is substantially flat without being high in the use frequency band.
[0050]
On the other hand, as shown in FIGS. 11 and 12, the input sound of the sound pressure P2
propagates from the eardrum E1 and the external ear canal E2 to the second acoustic space
232b via the second opening 231b, and is transmitted to the second sound collecting hole 221b.
Is also input.
[0051]
At this time, due to the Helmholtz resonance phenomenon, the sensitivity of the microphone 22
becomes high in a frequency band near the Helmholtz resonance frequency f2 of the input sound
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propagating to the second acoustic space 232b.
Here, as described above, the volume V2 of the second acoustic space 232b is much larger than
the volume V1 of the first acoustic space 232a. Therefore, the Helmholtz resonance frequency f2
appears in the use frequency band where the microphone 22 collects sound, as indicated by the
characteristic curve Cb in FIG. Therefore, the sensitivity of the microphone 22 in the used
frequency band is increased.
[0052]
Therefore, the difference in sensitivity of the microphone 22 to the input sound input to the first
and second sound collection holes 221a and 221b appears at least in the use frequency band of
the microphone 22. Therefore, the input voices input to the first and second sound collection
holes 221a and 221b do not cancel each other. Therefore, the microphone 22 can collect the
input voice. That is, the earphone microphone 1 can transmit input voice (such as the user's
speech) from an external sound source to an electronic device (not shown). << Echo component
suppression >>
[0053]
In practice, in the microphone 22, the output sound of the speaker 21 and the input sound from
an external sound source (such as the user's speech) are simultaneously collected. FIG. 14 is a
graph showing an example of the sensitivity characteristic of the microphone in the present
embodiment. The solid line C1 in FIG. 14 is a characteristic curve showing an example of the
frequency characteristic of the sensitivity of the microphone 22 when the output sound (or the
echo component thereof) of the speaker 21 is input to the microphone 22. A solid line C2 is a
characteristic curve showing an example of the frequency characteristic of the sensitivity of the
microphone 22 when the input voice from the external sound source (user's input voice) is input
to the microphone 22. The broken line C3 is a characteristic curve showing an example of the
frequency characteristic of the sensitivity of the microphone 22 to the input sound when the
earphone microphone 1 is worn on the ear.
[0054]
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In FIG. 14, the sensitivity of the characteristic curve C1 is 10 (dB) or more lower than the
characteristic curves C2 and C3 in the frequency band near the Helmholtz resonance frequency
f2 in the second acoustic space 232b. Thus, the earphone microphone 1 exhibits a good echo
suppression function.
[0055]
Further, in the characteristic curves C2 and C3, since the Helmholtz resonance frequency f2 is
around 1 kHz, a large sensitivity is obtained in a frequency band (for example, 1 to 2 kHz)
around the Helmholtz resonance frequency f2. Therefore, the earphone microphone 1 can
transmit input sound from an external sound source to the electronic device at a sound pressure
level according to the sensitivity of the microphone 22.
[0056]
In the characteristic curve C2, the sensitivity on the low frequency side of the microphone 22 is
lower than that on the high frequency side, but there is no problem in practice. This is because
when the earphone microphone 1 is worn on the ear (see FIG. 2), the sensitivity on the low
frequency side is high as shown by the characteristic curve C3 in FIG.
[0057]
As described above, in the present embodiment, the earphone microphone 1 includes the single
speaker 21, the microphone 22 (differential microphone) having the first and second sound
collection holes 221 a and 221 b, and the main body case 23. The body case 23 includes first
and second openings 231a and 231b communicating with the outside, a first acoustic space
232a communicating with the first opening 231a, and a second acoustic space communicating
with the second opening 231b. 232b are formed. The sound input to the first sound collecting
hole 221a propagates in the first acoustic space 232a. In the second acoustic space 232b, the
speaker 21 is disposed, and the sound input to the second sound collection hole 221b
propagates. In addition, the second acoustic space 232b functions as a Helmholtz resonator 7 for
the sound propagating through the second opening 231b.
[0058]
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In this configuration, the earphone microphone 1 includes one speaker 21. Further, the first and
second acoustic spaces 232a and 232b communicate with the outside of the main body housing
23 through the first and second openings 231a and 231b, respectively. In addition, the speaker
21 is disposed in the second acoustic space 232 b. In addition, the second acoustic space 232b
functions as a Helmholtz resonator 7 for the sound propagating through the second opening
231b. Therefore, the input sound from the external sound source resonates in the second
acoustic space 232b and then is input to the second sound collection hole 221b. At this time, in
the frequency band near the Helmholtz resonance frequency f2 in the second acoustic space
232b, a difference occurs in the sound pressure of the input sound input to the first and second
sound collection holes 221a and 221b. Therefore, the input voices input to the first and second
sound collection holes 221a and 221b are collected by the microphone 22 without canceling
each other. In addition, the output sound of the speaker 21 passes through the second sound
space 232 b, the second opening 231 b, the outside of the main body case 23, the first opening
231 a, and the first sound space 232 a to form a first sound collecting hole. Input to 221a. Also,
the output sound is directly input to the second sound collection hole 221 b in the second
acoustic space 232 b. Then, the output sound of the speaker 21 input to the first and second
sound collection holes 221a and 221b weakens each other, whereby the sound collection of the
output sound is suppressed. Therefore, the earphone microphone 1 can realize the echo
suppression function of the output sound of the speaker 21 without requiring the plurality of
speakers 21. Furthermore, the earphone microphone 1 can transmit input voice while
suppressing noise (echo component) derived from the output voice of the speaker 21.
Accordingly, it is possible to provide the earphone microphone 1 which can be miniaturized and
has an inexpensive echo suppression function.
[0059]
Further, in the present embodiment, the first acoustic space 232a functions as the Helmholtz
resonator 7 for the sound that propagates via the first opening 231a. Further, the volume V2 of
the second acoustic space 232b is larger than that of the first acoustic space 232a.
[0060]
In this configuration, the sound propagating from the outside of the main body casing 23 to the
first and second acoustic spaces 232a and 232b via the first and second openings 231a and
231b resonates by Helmholtz resonance. Furthermore, the volume V2 of the second acoustic
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space 232b is larger than the volume V1 of the first acoustic space 232a. Therefore, due to the
volume ratio (V2 / V1) of the first and second acoustic spaces 232a and 232b, the Helmholtz
resonance frequency f1 of the first acoustic space 232a is in a frequency band higher than the
Helmholtz resonance frequency f2 of the second acoustic space 232b. appear. Therefore, in the
frequency band including the Helmholtz resonance frequency f2 of the second acoustic space
232b, the input voices from the external sound sources input to the first and second sound
collection holes 221a and 221b can be prevented from mutually canceling each other . Since the
speaker 21 is disposed in the second acoustic space 232b, the output sound of the speaker 21
input to the second sound collection hole 221b does not resonate. Therefore, in the abovementioned frequency band, the output sound of the speaker 21 input to the first and second
sound collection holes 221a and 221b can be mutually weakened. Therefore, the earphone
microphone 1 can transmit input voice from an external sound source input to the microphone
22 while suppressing noise derived from the output voice of the speaker 21.
[0061]
Furthermore, in the present embodiment, the volume ratio (V2 / V1) of the first and second
acoustic spaces 232a and 232b is at least a predetermined frequency of sound propagating to
the first acoustic space 232a via the first opening 231a. It is set not to resonate in the band. Also,
the volume ratio (V2 / V1) is set so that the sound propagating in the second acoustic space
232b via the second opening 231b resonates within a predetermined frequency band. In this
way, it is possible to prevent the input sounds from the external sound sources input to the first
and second sound collection holes 221a and 221b from being canceled each other in a
predetermined frequency range. Furthermore, the output sound of the speaker 21 input to the
first and second sound collection holes 221a and 221b can be mutually weakened. Therefore, the
earphone microphone 1 can realize an echo suppression function in a predetermined frequency
range such as a use frequency band of the microphone 22.
[0062]
Further, in the present embodiment, the volume ratio (V2 / V1) of the second acoustic space
232b to the first acoustic space 232a is desirably 5 or more and 800 or less. In this case, the
Helmholtz resonance frequency f1 in the first acoustic space 232a is set to the first sound space
232a for the sound propagating to the first and second acoustic spaces 232a and 232b via the
first and second openings 231a and 231b. It can be made sufficiently larger than the Helmholtz
resonance frequency f2 in the two acoustic spaces 232b. Therefore, the earphone microphone 1
can reliably realize the echo suppression function.
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[0063]
Further, in the present embodiment, the Helmholtz resonance frequency f1 of the sound
propagating to the first acoustic space 232a via the first opening 231a is 4 kHz or more. Further,
the Helmholtz resonance frequency f2 of the sound propagating to the second acoustic space
232b via the second opening 231b is 1 kHz or more and 2 kHz or less. In this way, the Helmholtz
resonance frequency f1 of the sound propagating to the first acoustic space 232a via the first
opening 231a can be outside the use frequency band (for example, 300 Hz to 3.4 Hz) of the
microphone 22. Furthermore, the Helmholtz resonance frequency f2 of the sound propagating to
the second acoustic space 232b via the second opening 231b can be set within the working
frequency band of the microphone 22. Therefore, the earphone microphone 1 can transmit the
input voice from the external sound source input to the microphone 22 while suppressing the
noise derived from the output voice of the speaker 21 in the use frequency band of the
microphone 22.
[0064]
The embodiments of the present invention have been described above. It is to be understood by
those skilled in the art that the above-described embodiment is an exemplification, and that
various modifications can be made to the respective constituent elements and combinations of
the respective processes, and the present invention is within the scope of the present invention.
[0065]
For example, in the above-described embodiment, the main unit 2 incorporates the microphone
22 having the two sound collection holes 221a and 221b, but the scope of the present invention
is not limited to this example. A first microphone having a sound collecting hole 221a and a
second microphone having a second sound collecting hole 221b may be configured. In addition,
the earphone microphone 1 may generate a differential sound signal based on the first and
second sound signals by a control circuit unit (not shown). Alternatively, a differential sound
signal may be generated by an electronic device (not shown) to which the earphone microphone
1 is connected.
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[0066]
Moreover, in the above-mentioned embodiment, although the earphone microphone 1 is
equipped with one main-body part 2 like FIG. 1, the regular range of this invention is not limited
to this structure. The earphone microphone 1 may be provided with two main body parts 2.
Furthermore, one of the two body parts 2 may not have an echo suppression function. In other
words, on the other hand, the speaker 21 may be mounted but the microphone 22 may not be
mounted. In this way, the user can listen to the output sound of the earphone microphone 1 with
both ears.
[0067]
Further, in the above-described embodiment, the first acoustic space 232a functions as the
Helmholtz resonator 7, but the regular range of the present invention is not limited to this
configuration. The first acoustic space 232a may be an acoustic space functioning as a cylindrical
resonator. Even in such a case, since the first acoustic space 232a is minute, the resonance
frequency f1 in the first acoustic space 232a is outside the use frequency band of the
microphone 22 as in FIGS. 10 and 13. appear. Therefore, the echo suppression function for the
output sound of the speaker 21 can be realized, and the input sound in which the echo
component of the output sound is suppressed by the echo suppression function can be
transmitted to the electronic device (not shown).
[0068]
DESCRIPTION OF SYMBOLS 1 earphone microphone 2 main body part 21 speaker 21a sound
emitting hole 22 microphone 221a first sound collecting hole 221b second sound collecting hole
23 main body housing 23a insertion part 231a first opening 231b second opening 232a first
sound space 232b first 2 Sound space 25 Ear pad 4 Cable 5 Connector 7 Helmholtz resonator 71
Container 71a Opening 72 Neck EAR Ear E1 Eardrum E2 Ear canal
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