JP2009049844A - Bone conduction headphone apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bone conduction headphone apparatus that enables a user to bodily sense a stereoscopic sound field. <P>SOLUTION: The bone conduction headphone apparatus 100 has four bone conduction speakers which transduce sound information into mechanical vibrations. The bone conduction speakers 1 and 2 are put in contact with the head part F of the user nearby both the eyes. A bone conduction speaker 3 is put in contact with the forehead of the user. The bone conduction speaker 4 is put in contact with the occipital of the user. Consequently, the user is able to recognize "sound" not only from the right and left directions, but also from the front and back directions, so that the user can bodily sense a stereoscopic sound field in a more natural state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a bone conduction headphone device including a plurality of bone conduction speakers that convert sound information such as voice and music into mechanical vibration.

  Humans sense “sound” indirectly not only by “sound” coming directly into both ears but also by vibrations transmitted through the body. One of devices that transmit “sound” to a user using such a property is a bone conduction speaker. 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) via the skull and is perceived as “sound”.

  A bone conduction headphone device provided with such a bone conduction speaker is known. In the bone conduction headphone device, a pair of bone conduction speakers are arranged so as to abut on the vicinity of both ears of the user. Normally, two-channel stereo signals are input to the left and right bone conduction speakers. As a result, the user can experience a stereo sound field.

  Further, there is a demand for using a bone conduction headphone device so that a three-dimensional sound field can be experienced instead of a stereo sound field. Thus, attempts have been made to construct a three-dimensional sound field using left and right bone conduction speakers.

For example, a method of generating a pseudo multi-channel acoustic signal from a two-channel stereo signal and outputting the acoustic signal to the left and right bone conduction speakers is performed. For example, a pseudo multi-channel sound signal is obtained by adding a signal obtained by changing the phase characteristic or frequency characteristic of a two-channel stereo signal according to an actual three-dimensional sound field to the original two-channel sound signal. (For example, refer to Patent Documents 1 and 2).
WO95 / 20866 pamphlet JP 2001-218293 A

  However, considering the sound recognition mechanism by humans, it is difficult for the user to recognize the front and rear orientations of 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 an acoustic signal by this signal processing. Moreover, even if it is attempted to transmit a pseudo multi-channel acoustic signal using only the left and right bone conduction speakers, there are many cases where the sound is felt unnatural.

  This invention is made | formed in view of such a subject, and it aims at providing the bone-conduction headphone apparatus with which a user can experience a three-dimensional sound field more naturally.

  A bone conduction headphone device according to the present invention is a bone conduction headphone device including four or more bone conduction speakers for converting sound information into mechanical vibration, and is in contact with the vicinity of both ears of a user's head. A second bone conduction speaker; a third bone conduction speaker that abuts against the user's forehead; and a fourth bone conduction speaker that abuts against the user's occipital region.

  That is, the bone conduction headphone device of the present invention includes at least four bone conduction speakers. Of the four bone conduction speakers, two bone conduction speakers are arranged so as to abut one near the user's ears, and the other two bone conduction speakers are placed on the occipital and frontal areas of the user. It arrange | positions so that it may contact | abut one by one. In this way, the user receives mechanical vibrations corresponding to the left and right acoustic signals by the auditory organ via the skull, and mechanical vibrations corresponding to sound information also from the front and rear direction via the skull. Can be received by the auditory organ. As a result, the user can recognize “sound” not only in the left-right direction but also in the front-rear direction, so that the user can experience a three-dimensional sound field in a more natural state. .

  Furthermore, the third bone conduction speaker is disposed at a position higher 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, the mechanical vibrations emitted from the third and fourth bone conduction speakers can be received by the auditory organ from the vertical direction via the skull. As a result, the user can perceive “sound” from the top and bottom directions, so that the user can experience a three-dimensional sound field in a more natural state.

  Further, the apparatus further includes a signal processing device that outputs each of the four-channel acoustic signals to the corresponding bone conduction speaker, and the signal processing device inputs the four-channel acoustic signals to the second bone conduction speaker. Of the four-channel acoustic signals to the first bone-conduction speaker using a signal that is in phase opposite to the second acoustic signal and that takes into account the vibration attenuation characteristics of the user's head. Using a first correction unit that corrects an input first acoustic signal, a signal that is in phase opposite to the first acoustic signal, and that considers the vibration attenuation characteristics of the user's head, A second correction unit that corrects the second acoustic signal. This prevents crosstalk between the left and right acoustic signals in the user's head, which is caused by the vibration generated from the left and right bone conduction speakers being transmitted to the auditory organ of the opposite ear. Therefore, it is possible to prevent the user's sense of sound field from being lowered.

  Furthermore, the signal processing device may further include a low frequency emphasizing unit that emphasizes a frequency component lower than a predetermined frequency in the third and fourth acoustic signals among the acoustic signals of the four channels. . Since the vibration generated from the bone conduction speaker has good transfer characteristics in the human head in the low frequency region, if the low frequency components in the third and fourth acoustic signals are emphasized, the third, fourth, It becomes easier for the auditory organ to recognize “sound” caused by vibrations emitted from the bone conduction speaker, and the user can easily experience a three-dimensional sound field.

  Furthermore, the signal processing device further includes a frequency phase correction unit that generates the third and fourth acoustic signals by correcting the frequency phase characteristics of the first and second acoustic signals. Can do. In this way, the first and second acoustic signals, which are original two-channel stereo signals, and the third and fourth acoustic signals generated by correcting the frequency phase characteristics of the stereo signals are obtained. These are output to the first to fourth bone conduction speakers in contact with the corresponding binaural, frontal and occipital regions, respectively, and vibrations corresponding to the respective acoustic signals are transmitted from 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 the two-channel stereo signal.

  According to the bone conduction headphone device of the present invention, the user can experience a three-dimensional sound field in a more natural state.

  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, the bone conduction headphone device according to the embodiment of the present invention has bone conduction speakers arranged not only near the user's both ears but also in the frontal and occipital areas, and is close to the actual sound field. The user can experience a three-dimensional sound field.

  FIG. 1 (A) shows a front view of bone conduction headphones device 100 according to the present embodiment, and FIG. 1 (B) shows a side view of bone conduction headphones device 100 according to the present embodiment. FIG. 1C shows a top view of the bone conduction headphone device 100 according to the present embodiment. 1A to 1C show a state in which the bone conduction headphone device 100 is worn on the user's head F. FIG.

  As shown in FIG. 1 (A), FIG. 1 (B), and FIG. 1 (C) as a whole, the bone conduction headphone device 100 includes a bone conduction speaker 1 as a first 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 are configured. Yes. The bone conduction speakers 1 to 4 and the speaker support band 5 form a structure to be worn on the user's head F. The bone conduction headphone device 100 also includes a signal processing device 50 shown in FIG. 2 in addition to the signal processing device 50 shown in FIGS. 1 (A), 1 (B), and 1 (C). Is not shown).

  The bone conduction speaker 1 is disposed so as to contact the periphery of the right ear of the user's head F. In the vicinity of the contact portion in the bone conduction speaker 1, a vibrator is provided. 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 is recognized as “sound” obtained from the right ear of the user.

  The bone conduction speaker 2 is disposed so as to contact the periphery of the left ear of the user's head F. In the vicinity of the contact portion in the bone conduction speaker 2, a vibrator is provided. The bone conduction speaker 2 uses this vibrator to convert an electrical signal (acoustic signal) including sound information into mechanical vibration. This vibration is mainly transmitted to the auditory organ of the left ear and is recognized as “sound” obtained from the left ear of the user.

  The acoustic signal input to the bone conduction speaker 1 and the acoustic signal input to the bone conduction speaker 2 can have a difference in phase characteristics, frequency characteristics, and the like. It is a 2-channel stereo signal. Due to the difference in characteristics between the two acoustic signals, the user can recognize the sound field on the right side and the sound field on the left side.

  The bone conduction speaker 3 is arrange | positioned so that it may contact | abut to a user's forehead. In the vicinity of the contact portion in the bone conduction speaker 3, a vibrator is provided. 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 user's skull and recognized as “sound” emitted from the front of the user.

  The bone conduction speaker 4 is arrange | positioned so that it may contact | abut to a user's back head. 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 (acoustic signal) including sound information into mechanical vibration. This vibration is transmitted to the auditory organs of the left and right ears through the user's skull, and is recognized as “sound” emitted from the rear of the user.

  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 a difference in phase characteristics, frequency characteristics, and the like. ing. Due to the difference in characteristics between the two acoustic signals, the user can distinguish and recognize the front sound field and the rear sound field.

  In addition, 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 disposed at a position lower than the bone conduction speakers 1 and 2. Is arranged. In other words, in the present embodiment, the upper and lower arrangements of the bone conduction speaker 3 and the bone conduction speaker 4 are different. As a result, the user can obtain the upper sound field and the lower sound field due to the difference between the sound signal input to the bone conduction speaker 3 and the sound signal input to the bone conduction speaker 4. It becomes possible to distinguish and recognize.

  In the bone conduction speakers 1 to 4, for example, a piezoelectric element (electrostrictive element) or the like is used as a vibrator that converts an acoustic signal into mechanical vibration.

  As shown in FIG. 1C, the speaker support band 5 is formed in a cross shape when viewed from above, and bone conduction speakers 1 to 4 are connected to four tip portions extending in the cross shape, respectively. ing. Since the speaker support band 5 is made of an elastic material and is biased in a bending direction, when the bone conduction headphone device 100 is attached to the user's head F, the bone conduction speakers 1 to 1 are provided. 4 comes into contact with the user's head F, and good vibration transmission characteristics can be obtained.

  FIG. 2 shows the configuration of the signal processing device 50. 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 a two-channel stereo signal from the host device, and generates and outputs an acoustic signal to the bone conduction speakers 1 to 4 based on the stereo signal. In the following description, of the input two-channel stereo signals, a signal including sound information to be input to the right ear is referred to as a right stereo signal, and a signal including sound information to be input to the left ear is referred to as a left stereo signal. And

  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. It has. In the present embodiment, the head-related transfer characteristic correction circuit 6 and the adder 8 correspond to the first correction unit, and the head-related transfer characteristic correction circuit 7 and the adder 9 correspond to the second correction unit. The frequency / phase correction circuits 10 and 11 correspond to the frequency phase correction unit, and the low frequency emphasis circuits 12 and 13 correspond to the low frequency emphasis unit.

  As described above, 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, but these vibrations are transmitted via the skull. , Each will be transmitted to the ears on the opposite side. As a result, the “sound” transmitted in both ears interferes, and this interference reduces the user's sense of stereo sound field. The head-related transfer characteristic correction circuits 6 and 7 and the adders 8 and 9 are provided in order to prevent such a decrease in the sense of stereo sound field.

  The head-related transfer characteristic correction circuit 6 inputs a left stereo signal. The head-related transfer characteristic correction circuit 6 has a model of transfer characteristics 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 inputs a left stereo signal to this transfer characteristic model, and is equivalent to a vibration attenuation component transmitted from the bone conduction speaker 2 to the right ear hearing organ via the skull. Is output. The adder 8 adds and outputs the right stereo signal and a signal having a phase opposite to that of the signal output from the head-related transfer characteristic correction circuit 6 (a signal whose phase is shifted by 180 degrees).

  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 mainly transmitted to the auditory organ of the right ear, but is further transmitted to the auditory organ of the left ear via the user's skull.

  On the other hand, the head-related transfer characteristic correction circuit 7 inputs a right stereo signal. The head-related transfer characteristic correction circuit 7 has a model of transfer characteristics 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 a right stereo signal to this transfer characteristic model, and is equivalent to a vibration attenuation component transmitted from the bone conduction speaker 1 to the left ear auditory organ via the skull. Is output. The adder 9 adds the left stereo signal and a signal having an opposite phase to the signal output from the head-related transfer characteristic correction circuit 7 and outputs the result.

  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 left ear auditory organ via the skull in the user's head F, but is further transmitted to the right ear auditory organ via the user's skull. .

  As described above, the vibration output from the bone conduction speaker 1 includes the vibration component corresponding to the right stereo signal (this is referred to as “vibration component A”), and the vibration corresponding to the left stereo signal passes through the skull. Thus, the vibration component attenuated when it reaches the auditory organ of the right ear (this is referred to as “vibration component B”) is included. On the other hand, the vibration output from the bone conduction speaker 2 includes a vibration component corresponding to the left stereo signal (referred to as “vibration component C”), and this vibration is generated only by the left ear hearing organ. Instead, it reaches the auditory organ of the right ear via the skull with attenuation. The vibration component B and the vibration component C are almost the same component and are 180 degrees out of phase, so they cancel each other out and are actually recognized as “sound” by the right ear hearing organ. Is only “sound” by the right stereo signal corresponding to the vibration component A.

  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 is transmitted to the left ear via the skull. A vibration component for canceling the vibration component when reaching the auditory organ of the ear is also included. Therefore, this vibration component actually cancels the vibration component transmitted from the bone conduction speaker 1 via the skull to the left ear, and is actually recognized as “sound” by the left ear hearing organ. Is only “sound” by the left stereo signal. With the above configuration, a good stereo sound field is formed.

  The frequency / phase correction circuit 10 inputs two-channel stereo signals (right stereo signal and left stereo signal) and corrects their frequency characteristics and phase characteristics, thereby forming a sound field in front of the user. The acoustic signal is generated and output. The frequency / phase correction circuit 11 inputs a 2-channel stereo signal (right stereo signal, left stereo signal) and corrects their frequency characteristics and phase characteristics to form a sound field behind the user. A side acoustic signal is generated and output. These frequency / phase correction circuits 10 and 11 apply, for example, a pseudo multi-channel acoustic signal generation technique disclosed in Japanese Patent Application Laid-Open No. 2001-219293 and International Publication No. 95/20866. Since it is realizable, detailed description is abbreviate | omitted.

  The bone conduction speaker 3 is located above the user's ears. Based on the two-channel stereo signal (right stereo signal, left stereo signal), the frequency / phase correction circuit 10 adds an acoustic signal obtained by adding a component corresponding to the upper sound information to a component corresponding to the front sound information. Can be generated and output. Moreover, the bone conduction speaker 4 is located below the user's both ears. The frequency / phase correction circuit 11 generates an acoustic signal obtained by adding the lower sound information component to the rear sound information component based on the two-channel stereo signal (right stereo signal, left stereo signal). Can be output. In this way, the bone conduction speakers 3 and 4 can be used to allow the user to recognize the direction of the sound source in the vertical direction.

  The low-frequency emphasis circuit 12 is connected to the subsequent stage of the frequency / phase correction circuit 10 and has a low frequency component of a predetermined frequency (for example, 100 Hz) or less included in the front acoustic signal output from the frequency / phase correction circuit 10. To 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. Emphasizes low frequency components.

  In general, in bone conduction, it is possible to recognize the orientation of a sound source based on how vibrations are transmitted, but this effect is significant in a low frequency region. Therefore, the signal processing circuit 50 emphasizes the low frequency region components by the low frequency emphasizing circuits 12 and 13, and the bone conduction speakers 3 and 4 in which the vibrations in which the low frequency region components are emphasized are arranged before and after the head. Is generated. Thus, if the low frequency component of the acoustic signal input to the bone conduction speakers 3 and 4 having a relatively long distance to the auditory organ is emphasized, the user can more easily experience the front and rear sound fields. It becomes like this.

  As described above in detail, the bone conduction headphone device 100 according to the present embodiment includes the four bone conduction speakers 1 to 4. Of the four bone conduction speakers 1 to 4, the two bone conduction speakers 1 and 2 are arranged so as to abut on the vicinity of both ears of the user, and the remaining two bone conduction speakers 3 and 4 are the user's ears. It arrange | positions so that a back head and a front head may be contact | abutted. In this way, the user can receive the mechanical vibration corresponding to the sound information not only in the left-right direction but also in the front-rear direction with the auditory organ through the skull. As a result, the user can experience a three-dimensional sound field in a more natural state.

  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. Yes. In this way, the mechanical vibrations emitted from the bone conduction speakers 3 and 4 can be received by the auditory organ from the vertical direction via the skull. As a result, the user can also recognize the “sound” from the vertical direction, so that the user can experience a three-dimensional sound field in a more natural state.

  However, when there is no need 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.

  Further, the signal processing device 50 includes a head-related transfer characteristic correction circuit that corrects the right-side acoustic signal using a signal that has an opposite phase to the left-side acoustic signal and that takes into account the vibration attenuation characteristics of the user's head F. 6 and a head-related transfer characteristic correction circuit 7 that corrects the left-side acoustic signal using a signal that has an opposite phase to the right-side acoustic signal and that takes into account the vibration attenuation characteristics of the user's head F. ing. Thereby, the vibration generated from the left and right bone conduction speakers 1 and 2 is transmitted to the auditory organs of the opposite ear, and the interference of the left and right acoustic signals in the user's head F occurs. Therefore, it is possible to prevent the user's sense of sound field from being lowered.

  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 vibrations emitted from the bone conduction speakers 3 and 4 have good transmission characteristics in the user's head F in the low frequency region. Therefore, if the low frequency component is emphasized, the vibrations emitted from the bone conduction speakers 3 and 4. However, it becomes easier to be recognized as “sound” in the auditory organ.

  Further, the signal processing device 50 generates a 4-channel acoustic signal from the 2-channel stereo signal, and outputs the acoustic signal 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 two-channel stereo signals as acoustic signals to the bone conduction speakers 1 and 2 and the frequency / phase correction circuit 10. 11, the front and rear acoustic signals are generated by correcting the frequency phase characteristics of the stereo signal and 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 binaural signals. The bone conduction speakers 1 to 4 that come into contact with the forehead and the occipital region are output to each other, so that vibrations corresponding to the respective acoustic signals can be transmitted to the user's auditory organ from four directions. The user can experience a three-dimensional sound field.

  However, the four-channel acoustic signals input to the bone conduction speakers 1 to 4 do not have to be generated from a two-channel stereo signal, but a so-called four-channel acoustic signal originally generated as a four-channel acoustic signal. It may be a surround signal. In this case, the signal processing device 50 inputs these four-channel acoustic signals from the host device, and among the four-channel acoustic signals, the left and right acoustic signals are subjected to head-related transfer characteristic correction circuits 6 and 7 and an adder. 8 and 9, the bone conduction speakers 1 and 2 are output to the bone conduction speakers 1 and 2, and the acoustic signals before and after the bone conduction speaker 3 and the low frequency emphasis circuits 12 and 13 are emphasized. 4 may be output.

  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 device 100 abuts the user's head F with the four bone conduction speakers 1 to 4 so as to surround the head F from the four sides, the wearability to the head F is also good. . In addition, according to the bone conduction headphone device 100 according to the present embodiment, since measures such as preventing the interference of the left and right acoustic signals in the user's head F are taken, the left and right acoustic signals are A wide band can be obtained, 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 in a three-dimensional and high-quality sound field very easily.

  Note that the number of bone conduction speakers included in the bone conduction headphone device 100 according to the present embodiment is four, but it goes without saying that the number may be four or more.

FIG. 1 (A) is a front view of a bone conduction headphones device according to an embodiment of the present invention, FIG. 1 (B) is a side view of the bone conduction headphones device, and FIG. It is a top view of the bone conduction headphone device. It is an internal block diagram of a signal processing apparatus.

Explanation of symbols

1-4 Bone conduction speaker 5 Speaker support band 6, 7 Head transfer characteristic correction circuit 8, 9 Adder 10, 11 Frequency / phase correction circuit 12, 13 Low frequency emphasis circuit 50 Signal processing circuit 100 Bone conduction headphone device

Claims (5)

A bone conduction headphone device comprising four or more bone conduction speakers for converting sound information into mechanical vibration,
First and second bone conduction speakers that abut on the vicinity of both ears of the user's head;
A third bone conduction speaker that abuts the user's forehead;
A bone conduction headphone device comprising: a fourth bone conduction speaker that abuts on the occipital region of the user.   The third bone conduction speaker is arranged at a position higher than the first and second bone conduction speakers, and the fourth bone conduction speaker is lower than the first and second bone conduction speakers. The bone conduction headphones device according to claim 1, wherein A signal processing device that outputs each of the four-channel acoustic signals to the corresponding bone conduction speaker;
The signal processing device includes:
Among the acoustic signals of the four channels, using a signal having a phase opposite to that of the second acoustic signal input to the second bone conduction speaker and considering a vibration attenuation characteristic in the user's head A first correction unit that corrects a first acoustic signal input to the first bone conduction speaker among the acoustic signals of the four channels; an opposite phase to the first acoustic signal; and 3. The bone according to claim 1, further comprising: a second correction unit that corrects the second acoustic signal using a signal that takes into consideration a vibration attenuation characteristic in a user's head. 4. Conductive headphone device. The signal processing device includes:
It further has a low frequency emphasizing unit for emphasizing a frequency component lower than a predetermined frequency in the third and fourth acoustic signals input to the third and fourth bone conduction speakers among the four-channel acoustic signals. The bone conduction headphone device according to claim 3. The signal processing device includes:
5. The frequency phase correction unit for generating the third and fourth acoustic signals by correcting the frequency phase characteristics of the first and second acoustic signals is further provided. Bone conduction headphones device.

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