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JP2009049844

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DESCRIPTION JP2009049844
An object is to provide a bone conduction headphone device in which a user can experience a
three-dimensional sound field. A bone conduction headphone device (100) includes four bone
conduction speakers for converting sound information into mechanical vibration. The bone
conduction speakers 1 and 2 are abutted in the vicinity of both ears of the head F of the user.
The bone conduction speaker 3 is in contact with the forehead of the user. The bone conduction
speaker 4 is in contact with the back of the head of the user. As a result, the user can recognize
not only the left and right direction but also the "sound" from the front and back direction, so
that the user can experience the three-dimensional sound field in a more natural state. . [Selected
figure] Figure 1
Bone conduction headphone device
[0001]
The present invention relates to a bone conduction headphone device provided with a plurality of
bone conduction speakers that convert sound information such as voice and music into
mechanical vibration.
[0002]
Humans sense the sound indirectly not only by the sound coming directly into their ears, but also
by vibrations transmitted through the body.
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A bone conduction speaker is one of the devices that use such properties to convey "sound" to
the user. The bone conduction speaker is a conversion device that converts sound information
into mechanical vibration and transmits the vibration to the human head. This mechanical
vibration is transmitted to the auditory organ (cochlea) through the skull and becomes perceived
as "sound".
[0003]
A bone conduction headphone device provided with such a bone conduction speaker is known. In
a bone conduction headphone device, a pair of bone conduction speakers are arranged to abut in
the vicinity of the user's ears. Usually, two channels of stereo signals are input to the left and
right bone conduction speakers. This allows the user to experience the stereo sound field.
[0004]
There is also a demand for using a bone conduction headphone device to be able to experience a
three-dimensional sound field instead of a stereo sound field. Therefore, attempts have
conventionally been made to construct a three-dimensional sound field using the left and right
bone conduction speakers.
[0005]
For example, a method of generating pseudo multi-channel acoustic signals from two-channel
stereo signals and outputting the acoustic signals to the left and right bone conduction speakers
is performed. The pseudo multi-channel acoustic signal is, for example, adding a signal in which
the phase characteristic and frequency characteristic of the two-channel stereo signal are
changed according to the actual three-dimensional sound field to the original two-channel
acoustic signal. (See, for example, Patent Documents 1 and 2). International Publication No. WO
95/20866 Pamphlet JP 2001-218293 A
[0006]
However, considering the human recognition mechanism of sound, it is difficult for the user to
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recognize the direction before and after the sound source with only the left and right bone
conduction speakers mounted near both ears, and correction of frequency phase characteristics,
etc. It is known that there is a limit to pseudo multi-channeling of acoustic signals by signal
processing of In addition, even when trying to transmit pseudo multi-channel acoustic signals
using only the left and right bone conduction speakers, there are not a few cases where the
sound is perceived as unnatural.
[0007]
This invention is made in view of such a subject, and an object of this invention is to provide the
bone conduction headphone apparatus which a user can experience a three-dimensional sound
field more naturally.
[0008]
The bone conduction headphone apparatus according to the present invention is a bone
conduction headphone apparatus provided with four or more bone conduction speakers for
converting sound information into mechanical vibration, the first being abutted in the vicinity of
both ears of the user's head. A second bone conduction speaker, a third bone conduction speaker
in contact with the forehead of the user, and a fourth bone conduction speaker in contact with
the back of the head of the user.
[0009]
That is, the bone conduction headphone device of the present invention comprises at least four
bone conduction speakers.
Of the four bone conduction speakers, two bone conduction speakers are disposed so as to abut
each other in the vicinity of the user's ears, and the remaining two bone conduction speakers are
arranged on the back and front of the user It arrange | positions so that one piece may contact |
abut.
In this way, the user receives mechanical vibration corresponding to the left and right acoustic
signals by the auditory organ via the skull, and also receives mechanical vibration corresponding
to the sound information from the back and forth direction through the skull. Can be received by
the auditory organ. As a result, the user can recognize not only the left and right direction but
also the "sound" from the front and back direction, so that the user can experience the three-
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dimensional sound field in a more natural state. .
[0010]
Furthermore, the third bone conduction speaker is disposed at a higher position than the first
and second bone conduction speakers, and the fourth bone conduction speaker is more than the
first and second bone conduction speakers. It can be arranged at a low position. In this way, it is
possible to receive the mechanical vibration emitted from the third and fourth bone conduction
speakers by the auditory organ through the skull in the vertical direction. As a result, the user
can also perceive "sound" from the vertical direction, so that the user can experience a threedimensional sound field in a more natural state.
[0011]
The signal processing apparatus further includes a signal processing device that outputs each of
the four channels of acoustic signals to the corresponding bone conduction speaker, and the
signal processing device inputs one of the four channels of acoustic signals to the second bone
conduction speaker. The first bone conduction spy among the four channels of the acoustic
signal, using a signal that is in antiphase with the second acoustic signal to be transmitted and in
consideration of the attenuation characteristic of the vibration in the head of the user. A first
correction unit that corrects a first acoustic signal input to the first acoustic signal, a signal that
is in antiphase with the first acoustic signal, and in consideration of the attenuation characteristic
of the vibration of the head of the user And a second correction unit that corrects the second
acoustic signal. By this, it is possible to prevent the crosstalk of the left and right acoustic signals
in the head of the user, which is generated when the vibration emitted from one of the left and
right bone conduction speakers is transmitted to the auditory organ of the opposite ear. As a
result, it is possible to prevent a drop in the user's sense of sound field.
[0012]
Furthermore, the signal processing device may further include a low-frequency emphasis unit
that emphasizes a frequency component lower than a predetermined frequency in the third and
fourth acoustic signals among the four-channel acoustic signals. . The vibration generated from
the bone conduction speaker has a good transfer characteristic at the human head in the low
frequency region, so if the low frequency components in the third and fourth acoustic signals are
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emphasized, the third and fourth It becomes easy to recognize the "sound" by the vibration
emitted from the bone conduction speaker by the auditory organ, and the user can easily feel the
three-dimensional sound field.
[0013]
Furthermore, the signal processing apparatus further includes a frequency phase correction unit
that generates the third and fourth acoustic signals by correcting frequency phase characteristics
of the first and second acoustic signals. Can. In this way, the first and second acoustic signals,
which are the original two-channel stereo signals, and the third and fourth acoustic signals
generated by correcting the frequency phase characteristics of the stereo signals are: Output to
the corresponding first to fourth bone conduction speakers in contact with both ears, the
forehead, and the back of the head, and transmit vibrations corresponding to the respective
acoustic signals from the four directions to the user's auditory organ Will be able to As a result,
the user can experience a three-dimensional sound field based on a stereo signal of two channels.
[0014]
According to the bone conduction headphone device of the present invention, the user can
experience the three-dimensional sound field in a more natural state.
[0015]
Hereinafter, embodiments of a bone conduction headphone device according to the present
invention will be described in detail with reference to the drawings.
This bone conduction headphone device has four bone conduction speakers that convert sound
information into mechanical vibration. More specifically, in the bone conduction headphone
apparatus according to the embodiment of the present invention, bone conduction speakers are
disposed not only in the vicinity of the user's ears but also in the forehead and occipital region,
and are close to the actual sound field. It gives the user a three-dimensional sound field
experience.
[0016]
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FIG. 1 (A) shows a front view of the bone conduction headphone device 100 according to the
present embodiment, and FIG. 1 (B) shows a side view of the bone conduction headphone device
100 according to the present embodiment. FIG. 1C shows a top view of the bone conduction
headphone apparatus 100 according to the present embodiment. In FIGS. 1A to 1C, the bone
conduction headphone device 100 is shown mounted on the head F of the user.
[0017]
As generally shown in FIG. 1 (A), FIG. 1 (B), and FIG. 1 (C), the bone conduction headphone device
100 includes a bone conduction speaker 1 as a first bone conduction speaker, and a second bone
conduction speaker. A bone conduction speaker 2 as a bone conduction speaker, a bone
conduction speaker 3 as a third bone conduction speaker, a bone conduction speaker 4 as a
fourth bone conduction speaker, and a speaker support band 5 There is. The bone conduction
speakers 1 to 4 and the speaker support band 5 form a structure mounted on the head F of the
user. In addition, the bone conduction headphone device 100 also includes a signal processing
device 50 shown in FIG. 2, but the signal processing device 50 may be shown in FIGS. 1 (A), 1 (B),
1 (C). Not shown.
[0018]
The bone conduction speaker 1 is disposed to abut on the periphery of the right ear of the head F
of the user. A vibrator is provided near the contact portion in the bone conduction speaker 1. The
bone conduction speaker 1 uses this vibrator to convert an electrical signal (sound signal)
including sound information into mechanical vibration. This vibration is mainly transmitted to
the auditory organ of the right ear, and becomes recognized as "sound" obtained from the user's
right ear.
[0019]
The bone conduction speaker 2 is arranged to abut on the periphery of the left ear of the head F
of the user. A vibrator is provided near the contact portion in the bone conduction speaker 2. The
bone conduction speaker 2 uses this vibrator to convert an electrical signal (sound signal)
including sound information into mechanical vibration. This vibration is mainly transmitted to
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the auditory organ of the left ear, and becomes recognized as "sound" obtained from the user's
left ear.
[0020]
The acoustic signal input to the bone conduction speaker 1 and the acoustic signal input to the
bone conduction speaker 2 can be made to have differences in phase characteristics, frequency
characteristics, etc. It is a stereo signal of 2 channels. The difference in the characteristics of the
two acoustic signals enables the user to distinguish between the right sound field and the left
sound field.
[0021]
The bone conduction speaker 3 is disposed to abut on the forehead of the user. A vibrator is
provided near the contact portion in the bone conduction speaker 3. The bone conduction
speaker 3 uses this vibrator to convert an electrical signal (sound signal) including sound
information into mechanical vibration. This vibration is transmitted to the auditory organs of the
left and right ears via the skull of the user and is recognized as "sound" emitted from the front of
the user.
[0022]
The bone conduction speaker 4 is disposed to abut on the back of the head of the user. A vibrator
is provided near the contact portion in the bone conduction speaker 4. The bone conduction
speaker 4 uses this vibrator to convert an electrical signal (sound signal) including sound
information into mechanical vibration. This vibration is transmitted to the auditory organs of the
left and right ears via the skull of the user and is recognized as "sound" emitted from the back of
the user.
[0023]
As will be described later, the acoustic signal input to the bone conduction speaker 3 and the
acoustic signal input to the bone conduction speaker 4 can have differences in phase
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characteristics, frequency characteristics, etc. ing. The difference in the characteristics of the two
acoustic signals enables the user to distinguish and recognize the front sound field and the rear
sound field.
[0024]
Further, as shown in FIG. 1B, the bone conduction speaker 3 is disposed at a position higher than
the bone conduction speakers 1 and 2, and the bone conduction speaker 4 is at a position lower
than the bone conduction speakers 1 and 2. It is arranged. That is, in the present embodiment,
the arrangement of the bone conduction speaker 3 and the arrangement of the bone conduction
speaker 4 are different. Thus, the user can recognize the upper sound field and the lower sound
field by the difference between the acoustic signal input to the bone conduction speaker 3 and
the acoustic signal input to the bone conduction speaker 4. It becomes possible to distinguish
and recognize.
[0025]
In the bone conduction speakers 1 to 4, for example, a piezoelectric element (electrostrictive
element) or the like is used as a vibrator for converting an acoustic signal into mechanical
vibration.
[0026]
As shown in FIG. 1C, the speaker support band 5 is formed in a cross shape as viewed from the
top, and the bone conduction speakers 1 to 4 are connected to the four tip portions extending in
the cross, respectively. ing.
Since the speaker support band 5 is made of a resilient material and biased in a bending
direction, when the bone conduction headphone device 100 is mounted on the head F of the
user, the bone conduction speaker 1 to 1 can be used. 4 comes into contact with the head F of
the user, so that good vibration transmission characteristics can be obtained.
[0027]
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The configuration of the signal processing device 50 is shown in FIG. As shown in FIG. 2, the
signal processing device 50 is connected to the bone conduction speakers 1 to 4. The signal
processing device 50 receives stereo signals of two channels from the host device, and generates
and outputs acoustic signals to the bone conduction speakers 1 to 4 based on the stereo signals.
In the following, among the input two-channel stereo signals, a signal including sound
information to be input to the right ear is a right stereo signal, and a signal including sound
information to be input to the left ear is a left stereo signal I assume.
[0028]
As shown in FIG. 2, the signal processing device 50 includes head-related transfer characteristic
correction circuits 6 and 7, adders 8 and 9, frequency / phase correction circuits 10 and 11, and
low-frequency emphasis circuits 12 and 13. Is equipped. In the present embodiment, the headrelated transfer characteristic correction circuit 6 and the adder 8 correspond to a first
correction unit, and the head-related transfer characteristic correction circuit 7 and the adder 9
correspond to a second correction unit. Also, the frequency / phase correction circuits 10 and 11
correspond to the frequency phase correction unit, and the low band emphasis circuits 12 and
13 correspond to the low band emphasis part.
[0029]
As described above, although the vibration corresponding to the left stereo signal is mainly
transmitted to the left ear and the vibration corresponding to the right stereo signal is mainly
transmitted to the right ear, those vibrations are transmitted via the skull. , Will also be
transmitted to the opposite ear. This causes interference in the transmitted "sound" in both ears,
and this interference degrades the user's sense of stereo sound field. The head-related transfer
characteristic correction circuits 6, 7 and the adders 8, 9 are provided to prevent such
deterioration of the stereo sound field feeling.
[0030]
The head-related transfer characteristic correction circuit 6 receives a left stereo signal. The
head-related transfer characteristic correction circuit 6 has a model of the transfer characteristic
when the left stereo signal is transmitted from the bone conduction speaker 2 to the auditory
organ of the right ear via the skull. The head-related transfer characteristic correction circuit 6
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inputs the left stereo signal to the model of the transfer characteristic, and the component
equivalent to the attenuation component of the vibration transmitted from the bone conduction
speaker 2 to the auditory organ of the right ear via the skull Output a signal having The adder 8
adds and outputs the right stereo signal and a signal (a signal whose phase is shifted 180
degrees) in the reverse phase of the signal output from the head-related transfer characteristic
correction circuit 6.
[0031]
The signal output from the adder 8 is finally output to the bone conduction speaker 1. The bone
conduction speaker 1 converts this signal into mechanical vibration. This vibration is transmitted
mainly to the auditory organ of the right ear, but is also transmitted to the auditory organ of the
left ear via the skull of the user.
[0032]
On the other hand, the head-related transfer characteristic correction circuit 7 receives the right
stereo signal. The head-related transfer characteristic correction circuit 7 has a model of the
transfer characteristic when the right stereo signal is transmitted from the bone conduction
speaker 1 to the auditory organ of the left ear via the skull. The head-related transfer
characteristic correction circuit 7 inputs the right stereo signal to the model of the transfer
characteristic, and the component equivalent to the attenuation component of the vibration
transmitted from the bone conduction speaker 1 to the auditory organ of the left ear via the skull
Output a signal having The adder 9 adds the left stereo signal and the signal of the reverse phase
of the signal output from the head-related transfer characteristic correction circuit 7 and outputs
the result.
[0033]
The signal output from the adder 9 is finally output to the bone conduction speaker 2. The bone
conduction speaker 2 converts this signal into mechanical vibration. This vibration is mainly
transmitted to the auditory organ of the left ear via the skull in the head F of the user, and is
further transmitted to the auditory organ of the right ear via the skull of the user .
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[0034]
As described above, in the vibration output from the bone conduction speaker 1, in addition to
the vibration component corresponding to the right stereo signal (this is referred to as
“vibration component A”), the vibration corresponding to the left stereo signal passes through
the skull. Then, a damped vibration component (this is referred to as “vibration component B”)
when it reaches the auditory organ of the right ear is included. On the other hand, the vibration
output from the bone conduction speaker 2 includes a vibration component (this is referred to as
“vibration component C”) corresponding to the left stereo signal, and this vibration is
generated only by the auditory organ of the left ear. It also reaches the auditory organ of the
right ear via the skull while decaying. The vibration component B and the vibration component C
are substantially the same component and are 180 degrees out of phase, so they cancel each
other out and are actually recognized as "sound" by the auditory organ of the right ear Is only the
"sound" by the right stereo signal corresponding to the vibration component A.
[0035]
Similarly, for the left ear, not only the vibration component corresponding to the left stereo
signal but also the vibration corresponding to the right stereo signal from the bone conduction
speaker 1 passes through the skull via the skull in the vibration emitted from the bone
conduction speaker 2 A vibration component is also included to cancel the vibration component
when it reaches the ear's auditory organ. Therefore, this vibration component actually cancels
the vibration component transmitted from the bone conduction speaker 1 to the left ear via the
skull, and is actually recognized as "sound" by the auditory organ of the left ear Is the only
"sound" from the left stereo signal. With the above configuration, a good stereo sound field is
formed.
[0036]
The frequency / phase correction circuit 10 inputs stereo signals (right stereo signal and left
stereo signal) of two channels and corrects their frequency characteristics and phase
characteristics to form a sound field in front of the user. Generate and output an acoustic signal
of The frequency / phase correction circuit 11 inputs stereo signals (right stereo signal and left
stereo signal) of two channels and corrects their frequency characteristics and phase
characteristics to form a sound field behind the user. Generates and outputs an audio signal on
the side. These frequency / phase correction circuits 10 and 11 can be generated by applying the
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pseudo multi-channel acoustic signal generation technology disclosed in, for example, Japanese
Patent Application Laid-Open No. 2001-219293 and International Publication No. 95/20866
pamphlet. As it can be realized, the detailed description is omitted.
[0037]
The bone conduction speaker 3 is located above the user's ears. The frequency / phase
correction circuit 10 adds the component corresponding to the sound information on the upper
side to the component corresponding to the sound information on the front side based on the
stereo signals (right stereo signal and left stereo signal) of two channels. It can be generated and
output. The bone conduction speaker 4 is located below the user's ears. The frequency / phase
correction circuit 11 generates an acoustic signal in which the component of the sound
information on the lower side is added to the component of the sound information on the rear
side based on the stereo signals (right stereo signal and left stereo signal) of two channels. Can
be output. In this way, it is possible to make the user recognize the direction of the sound source
in the vertical direction by using the bone conduction speakers 3 and 4.
[0038]
The low band emphasizing circuit 12 is connected to the subsequent stage of the frequency /
phase correction circuit 10, and is a low frequency component equal to or less than a
predetermined frequency (eg, 100 Hz) included in the front acoustic signal output from the
frequency / phase correction circuit 10. Emphasize. The low-frequency emphasis circuit 13 is
connected to the subsequent stage of the frequency / phase correction circuit 11 and has a
predetermined frequency (for example, 100 Hz) or less included in the rear acoustic signal
output from the frequency / phase correction circuit 11. Emphasize low frequency components.
[0039]
Generally, in bone conduction, it is possible to recognize the direction of a sound source
depending on how vibration is transmitted, but this effect is remarkable in the low frequency
region. Therefore, in the signal processing circuit 50, the low frequency emphasizing circuits 12
and 13 emphasize the low frequency range component, and the bone conduction speakers 3 and
4 arrange the vibration in which the low frequency range component is emphasized on the front
and back of the head. It is generated. By emphasizing the low frequency components of the
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acoustic signal input to the bone conduction speakers 3 and 4 having a relatively long distance to
the auditory organ in this manner, the user can more easily feel the front and back sound fields.
It will be.
[0040]
As described above in detail, the bone conduction headphone apparatus 100 according to the
present embodiment includes the four bone conduction speakers 1 to 4. Of the four bone
conduction speakers 1 to 4, two bone conduction speakers 1 and 2 are arranged to abut in the
vicinity of the user's ears, and the remaining two bone conduction speakers 3 and 4 are used by
the user. It is arranged to abut the occipital region and the forehead region. In this way, the user
can receive the mechanical vibration corresponding to the sound information by the auditory
organ via the skull not only in the lateral direction but also in the longitudinal direction. As a
result, the user can experience a three-dimensional sound field in a more natural state.
[0041]
Furthermore, according to the present embodiment, the bone conduction speaker 3 is disposed at
a position higher than the bone conduction speakers 1 and 2, and the bone conduction speaker 4
is disposed at a position lower than the bone conduction speakers 1 and 2. There is. In this way,
it is possible to receive the mechanical vibration emitted from the bone conduction speakers 3
and 4 by the auditory organ through the skull in the vertical direction. As a result, the user can
also recognize "sounds" in the vertical direction, so that the user can experience a threedimensional sound field in a more natural state.
[0042]
However, when it is not necessary to construct a sound field in the vertical direction, the bone
conduction speaker 3 and the bone conduction speaker 4 may be arranged at the same height.
[0043]
Furthermore, the signal processing device 50 is a head-related transfer characteristic correction
circuit that corrects the sound signal on the right side using a signal that is in antiphase with the
sound signal on the left side and that takes into account the vibration attenuation characteristic
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of the head F of the user. 6 and a head transfer characteristic correction circuit 7 for correcting
the sound signal on the left side using a signal that is in antiphase with the sound signal on the
right side and in consideration of the vibration attenuation characteristic of the head F of the
user ing.
As a result, the vibration generated from the left and right bone conduction speakers 1 and 2 is
generated by being transmitted to the auditory organ of the opposite ear, and the crosstalk of the
left and right acoustic signals in the head F of the user As a result, it is possible to prevent a drop
in the user's sense of sound field.
[0044]
Furthermore, the signal processing device 50 includes low-frequency emphasis circuits 12 and
13 that emphasize low-frequency components of the front and rear acoustic signals. The
vibration generated from the bone conduction speakers 3 and 4 has a good transmission
characteristic at the head F of the user in the low frequency region, so if the low frequency
component is emphasized, the vibration generated from the bone conduction speakers 3 and 4
But are more likely to be recognized as "sounds" in the auditory organ.
[0045]
Furthermore, the signal processing device 50 generates acoustic signals of four channels from
stereo signals of two channels, and outputs the acoustic signals of each channel to the
corresponding bone conduction speakers 1 to 4. More specifically, the signal processing device
50 outputs a right stereo signal and a left stereo signal as stereo signals of two channels as an
acoustic signal to the bone conduction speakers 1 and 2, and the frequency / phase correction
circuit 10 11 correct the frequency phase characteristics of the stereo signal to generate front
and rear acoustic signals, which are output to the bone conduction speakers 3 and 4. In this way,
the left and right acoustic signals, which are the original two-channel stereo signals, and the front
and rear acoustic signals generated by correcting the frequency phase characteristics of the
stereo signals correspond to the corresponding two ears. , As it is output to the bone conduction
speakers 1 to 4 in contact with the forehead and occipital region, and it becomes possible to
transmit vibration corresponding to each acoustic signal to the user's auditory organ from four
directions. The user can experience a three-dimensional sound field.
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[0046]
However, the four-channel acoustic signals input to the bone conduction speakers 1 to 4 do not
have to be generated from two-channel stereo signals, and so-called four-channel acoustic signals
originally generated as four-channel acoustic signals. It may be a surround signal. In this case,
the signal processing device 50 receives the four-channel acoustic signal from the host device,
and among the four-channel acoustic signals, the head-related transfer characteristic correction
circuits 6, 7 and an adder for the left and right acoustic signals. After correction by 8, 9 is output
to the bone conduction speakers 1, 2, and for the front and back acoustic signals, the bone
conduction speaker 3, after emphasizing low frequency components using the low-frequency
emphasis circuits 12, 13. It is sufficient to output to 4.
[0047]
Since the bone conduction headphone device 100 is small and light, the user can easily obtain a
three-dimensional sound field. In addition, since the bone conduction headphone apparatus 100
abuts the head F of the user with the four bone conduction speakers 1 to 4 so as to surround the
head from four sides, the mountability to the head F is also excellent. . Further, according to the
bone conduction headphone device 100 according to the present embodiment, since measures
are taken to prevent interference between the left and right acoustic signals in the head F of the
user, the left and right acoustic signals can be A wide band can be used, and the frequency
characteristics can be improved. As described above, by using the bone conduction headphone
device according to the present embodiment, the user can enjoy music and the like very easily in
a three-dimensional and high-quality sound field.
[0048]
Although the number of bone conduction speakers included in the bone conduction headphone
apparatus 100 according to the present embodiment is four, it is needless to say that the number
may be four or more.
[0049]
FIG. 1 (A) is a front view of a bone conduction headphone device according to an embodiment of
the present invention, FIG. 1 (B) is a side view of the bone conduction headphone device, and FIG.
1 (C) is It is a top view of the bone conduction headphone device.
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It is an internal block diagram of a signal processing device.
Explanation of sign
[0050]
1 to 4 bone conduction speakers 5 speaker support bands 6, 7 head transmission characteristic
correction circuits 8, 9 adders 10, 11 frequency / phase correction circuits 12, 13 low-frequency
emphasis circuits 50 signal processing circuits 100 bone conduction headphone devices
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