JP2004158961A - Headphone device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a headphone device for irradiating a human body with an ultrasonic wave which has been amplitude-modulated by an audible signal to generate an audible sound in the human body, which can provide only audible tone vibration without applying ultrasonic wave vibration to the human body. <P>SOLUTION: The device consists of an ultrasonic wave signal generating means for generating an ultrasonic wave signal having a higher frequency than that in an audible band; modulating means for applying amplitude modulation to the ultrasonic signal by a sound signal in the audible band to obtain a modulated signal; exciting means for generating non-audible vibration by the modulated signal; vibrating member contacting the exciting means and consisting of any one of a natural cartilage and a reproduced cartilage, which is approximately equal to the acoustic impedance of the human body and has non-linear characteristics between a contact acceleration and the amplitude of acoustic output, and resin material having a Young's modulus of 0.5×10<SP>6</SP>-0.5×10<SP>8</SP>Pa; and a casing for storing the exiting means with the vibration surface of the exciting means upward. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a headphone device that can be used to apply vibration to a part of a human body and perceive the vibration as sound.
[0002]
[Prior art]
A bone conduction transmission method has been put to practical use as one of the methods for causing humans to perceive sound. The bone conduction transmission method is a method in which acoustic vibration is mainly applied to the head of a human body, and this acoustic vibration is transmitted to the auditory system through bones, flesh, and the like of the human body to be perceived as sound. According to this bone conduction transmission method, it is possible to make a person who is deaf can perceive a sound.
In order to realize the bone conduction transmission method, a method of generating acoustic vibration at an audible frequency by a vibrating means and applying the acoustic vibration to a human head may be considered. When this method is used, there is a disadvantage that acoustic vibration leaks to the surroundings and can be heard as noise by surrounding people.
Therefore, an ultrasonic signal that is non-audible is amplitude-modulated with an audible signal, the ultrasonic transducer is driven by the amplitude-modulated ultrasonic signal, and the head of the human body is applied with the amplitude-modulated ultrasonic vibration. A method of demodulating audible vibrations by demodulation of ultrasonic waves inside the human body by shaking and transmitting the audible vibrations to the auditory system has also been considered. According to the ultrasonic bone transmission method, there is an advantage that sound does not leak to the surroundings.
[0003]
FIG. 22 shows a schematic configuration of the ultrasonic bone conduction headphone. The vibration means 1 capable of vibrating in a non-audible band (ultrasonic band) is brought into contact with the skin, and is mounted so as to vibrate a human body. The non-audible ultrasonic signal of about 20 kHz to 50 kHz output from the ultrasonic signal generation means 2 is amplitude-modulated by the amplitude modulation means 4 by the input signal 3 which is an audible signal, and is input to the vibration means 1. The non-audible vibration transmitted to the human body from the vibration means 1 generates an audible vibration by a non-linear effect and can be perceived as sound. The generated audible vibration is a vibration corresponding to the input signal 3 used for the modulation. Therefore, by using a signal such as music or voice as the input signal 3, it is possible to produce a bone conduction headphone device capable of listening to music or voice.
However, conventional bone conduction headphones convert non-audible vibrations of the vibration means 1 into audible vibrations by a non-linear effect in the human body, so that it is necessary to transmit high-energy non-audible vibrations to the human body. There was the first problem of this.
Further, in the conventional bone conduction headphones, the acoustic impedance of the vibration means 1 itself and the acoustic impedance of the human body greatly differ depending on the material, and the vibration energy is reflected on the contact surface between the vibration means 1 and the human body, and the vibration is efficiently performed. There was a second problem that it could not be transmitted to the human body.
[0004]
In order to solve these problems, the applicant of the present invention has an electroacoustic transducer having a structure in which a vibration material whose acoustic impedance is substantially equal to the acoustic impedance of the human body is interposed between the vibration means 1 and the human body (Japanese Patent Application No. 2001-38631). Suggested.
According to the electro-acoustic transducer proposed in the prior application, the transmission efficiency of audible vibration can be improved and the excitation amplitude of non-audible vibration can be reduced by sandwiching the vibration material between the vibration means and the human body. . As a result, the above-described first problem and second problem can be solved.
In the invention of the prior application, a polymer gel material is cited as a material having an acoustic impedance substantially equal to that of the human body as an actually used vibration material and having a non-linear acoustic characteristic.
[0005]
[Problems to be solved by the invention]
In the electro-acoustic transducer proposed in the prior application, although the acoustic impedance of the vibrating material is almost equal to the acoustic impedance of the human body, the third problem has occurred in that the nonlinear efficiency is low and audible vibration does not efficiently occur in the vibrating material. .
An object of the present invention is to provide a headphone device capable of efficiently generating audible vibration in a vibration material and solving the third problem.
[0006]
[Means for Solving the Problems]
According to the present invention, an ultrasonic signal generating means for generating an ultrasonic signal having a frequency higher than at least the audible region, a modulating means for amplitude-modulating the ultrasonic signal with an audio signal in the audible region to obtain a modulated signal, Exciting means for generating non-audible vibration by a signal, either natural cartilage or regenerated cartilage which is in contact with the exciting means and has a non-linear characteristic between the contact acceleration and the amplitude of the sound output substantially equal to the acoustic impedance of the human body. A headphone device comprising: a vibration material configured as described above; and a housing for storing the vibration means with the vibration surface of the vibration means as a surface.
[0007]
The present invention further provides an ultrasonic signal generating means for generating an ultrasonic signal having a frequency higher than at least the audible region, a modulating means for amplitude-modulating the ultrasonic signal with an audio signal in the audible region to obtain a modulated signal, Exciting means that generates non-audible vibrations by the modulation signal, and a Young's modulus having a non-linear characteristic between the contact acceleration and the amplitude of the acoustic output that is approximately equal to the acoustic impedance of the human body and is in contact with the exciting means, is 0.5 × A headphone device including a vibration material having a pressure of 10 ^{6 to} 0.5 × 10 ⁸ Pa and a housing for storing the vibration means with the vibration surface of the vibration means as a surface is proposed.
[0008]
Action <br/> natural cartilage or regenerated cartilage as a vibration element according to the present invention, or from Young's modulus using a material of ^{0.5 × 10 6 ~0.5 × 10 8} Pa, these materials are non-linear efficiency Therefore, audible vibration is generated with high efficiency inside the vibration material, and as a result, the third problem can be solved. Therefore, according to the present invention, it is possible to realize a headphone device with high efficiency, less sound leakage, and less burden on the human body.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an embodiment of the present invention. According to the present invention, the vibration device 5 is extended from the conventional device shown in FIG. Here, as the vibration material 5, for example, natural cartilage collected from animal ears or the like or artificially produced regenerated cartilage or a Young's modulus of 0.5 × 10 ^{6 to} 0.5 × 10 ⁸ Pa and a specific gravity of 0 It can be made of a resin material such as an elastomer having a thickness of 0.5 to 2.5. When the vibration material 5 is disposed, the vibration of the vibration means 1 is transmitted to the human body via the vibration material 5. The vibrating means 1 does not directly vibrate the human body, but vibrates the vibration material 5 with vibration in a non-audible band. In the case of driving using a signal in which an ultrasonic signal in a non-audible band is amplitude-modulated with an audible signal as a signal for vibrating the vibration means 1, the non-audible vibration is transmitted to the human body due to the non-linearity of the vibration material 5 due to the non-linearity of the vibration material 5. An audible vibration is generated inside the camera.
By using a resin material such as the above-described natural cartilage, regenerated cartilage, or elastomer for the vibration material 5, audible vibration can be generated efficiently, and these materials have an acoustic impedance with cartilage or skin of a human body. Since it is close, the audible vibration generated in the vibration material 5 can be efficiently transmitted to the human body without being attenuated at the boundary with the human body. Further, since the non-audible vibration of high energy is attenuated inside the vibration material 5, the non-audible vibration is hardly transmitted to the human body, and the burden on the human body is reduced.
[0010]
2 and 3 show an embodiment of the vibration means 1 and the vibration material 5. The vibrating means 1 is composed of, for example, a disk-shaped piezoelectric vibration element, and a metal plate such as aluminum is adhered to the surface of the piezoelectric vibration element to form a vibration surface 1A. The vibration means 1 is stored in a cup-shaped housing 1B made of, for example, a hard plastic.
The diameter D1 of the vibration surface 1A of the vibration means 1 is about 15 mm, and the vibration material 5 is adhered to the vibration surface 1A with an adhesive 5C. As the adhesive 5C, for example, a rubber-based pressure-sensitive adhesive can be used.
A case where natural cartilage or regenerated cartilage is used as the vibration material 5 will be described. Natural cartilage can be collected, for example, from ears of animals such as pigs. The collected natural cartilage is cut into a disk shape having a diameter D2 = about 16 to 17 mm slightly larger than the diameter D1 of the vibration surface 1A of the vibration means 1 by, for example, about 1 to 2 mm and a thickness T of about 2 to 5 mm. The surface of natural cartilage or regenerated cartilage 5A (see FIG. 3) cut into a desired shape is wrapped with, for example, a polypropylene wrap material 5B having a thickness of about several microns, vacuum-sealed, and sealed.
One circular surface of the vibrating material 5 wrapped with the wrapping material 5B is adhered to the vibrating surface 1A of the vibration means 1 with an adhesive 5C. By virtue of this bonding, one circular surface of the vibrating material 5 is vibrated by the non-audible vibration of the vibrating surface 1A of the vibrating means 1 whose amplitude has been modulated, so that the natural cartilage 5A has its thickness T (see FIG. 2) in the middle thereof. As a result, acoustic vibration is reproduced due to the nonlinear characteristics of natural cartilage, and the surface side of the vibration material 5 acoustically vibrates. This acoustic vibration is transmitted to the human body and is perceived as sound.
[0011]
For comparison, FIG. 4 shows an example of the measurement result of the demodulated vibration due to the difference in the material of the vibration material 5. For comparison, the intensity of the ultrasonic vibration (non-audible vibration) to be excited is set to be the same, and the demodulated vibration acceleration of each material is calculated. The accelerometer was directly installed at almost the same position in the measurement. The measurement was performed with the frequency of the audible signal used for amplitude modulation being a sinusoidal vibration of 250 Hz to 4 kHz and the frequency of the ultrasonic signal being 40 kHz.
Curve A shown in FIG. 4 shows the measured value of the acceleration of the ultrasonic vibration.
Curve B is the measured acceleration value of the demodulated vibration generated in the natural cartilage,
Curve C is the measured acceleration value of the demodulated vibration generated in the polymer gel,
Are respectively shown.
From this measurement result, it can be seen that demodulation efficiency is improved by about 20 to 30 dB by using natural cartilage as the vibration material 5 as compared with the case of the polymer gel.
2 and 3, the inside of the vibration material 5 is described as natural cartilage or regenerated cartilage, but the Young's modulus is 0.5 × 10 ^{6 to} 0.5 × 10 ⁸ Pa and the specific gravity is about 0.5 to 2.5. A resin material such as an elastomer can be used.
[0012]
FIGS. 5 and 6 show an example of mounting the headphone device according to the present invention on a human body. 5 and 6 show a headphone device according to the present invention. As described above, the headphone device 10 according to the present invention includes the vibration means 1 and the vibration material 5 mounted on the vibration surface of the vibration means 1.
Reference numeral 11 denotes a headband. Hinges 12 are attached to both ends of the headband 11 (only one end is shown in the figure). A lever 13 is attached to the hinge 12, and the free end of the lever 13 is constantly pressed against a portion near the ear of the wearer by a spring mounted on the hinge 12. A support rod 14 is further mounted on the lever 13, and a headphone device 10 is mounted on the lower end of the support rod 14, and the vibration material 5 mounted on the vibration surface thereof is pressed against the skin of the wearer.
[0013]
FIG. 7 shows another embodiment of the headphone device according to the present invention. This embodiment proposes a headphone device capable of controlling sound quality. In general, the vibration means 1 capable of generating ultrasonic vibration does not have a flat acoustic frequency characteristic. Also, the relationship between the input voltage and the excitation power as the output is often not linear. Therefore, even when vibration is transmitted to the human body by ultrasonic waves, distortion is likely to occur, and it is difficult to control sound quality. Therefore, by correcting the signal or the like input to the vibration means 1 by the correction means 6, the frequency characteristic of the audible sound generated by the non-linear effect can be made flat.
[0014]
An example of a method in the case where the correction is performed by the correction unit 6 will be described below. The frequency characteristic of the audible sound generated inside the vibration material 5 due to the non-linear effect of the ultrasonic wave is theoretically approximately proportional to the square of the frequency ω when the modulation depth is constant. Characteristics. In FIG. 8, the lowest frequency of the audible sound to be generated is ωL (for example, 20 Hz), and the highest frequency is ωH (for example, 20 Hz).
Assuming that the frequency characteristic of the vibration means 1 has a flat characteristic over ± 20 KHz around the frequency of the ultrasonic wave (the frequency of the carrier), the audible vibration reproduced from the non-audible vibration has the frequency shown in FIG. It has a frequency characteristic proportional to the square (ω ² ). In order to correct this frequency characteristic and obtain a flat frequency characteristic, it is necessary for the correction means 6 to have a 1 / ω ² characteristic.
[0015]
Incidentally, the entire system configuration is as listed in Figure 7, the frequency characteristics of the vibration means 1 is not flat within the required band as shown various in FIG. 9 and symmetrically around the resonance frequency omega ₀ attenuation The curves A1, A2, and A3 shown in FIG. 9 indicate the frequency characteristics of the ultrasonic output for each type of ultrasonic transducer.
When the vibration unit 1 has the frequency characteristics of a general ultrasonic transducer, the correction unit 6 is required to have a characteristic different from the above-described 1 / ω ² characteristic.
Now, assuming that the amplitude frequency characteristic of the vibration means 1 is A (ω), a target characteristic centered on the resonance frequency, that is, A (ω ₀ + ω) = A (ω ₀ −ω). Further, if A (ω) is normalized so that A (ω ₀ ) = 1, the characteristic of the correcting means 6 in this case is 1 / (A (ω ₀ + ω) ω ² ). Therefore, as shown in FIG. 10, when the equivalent low-frequency characteristic H ₁ (ω) of the amplitude frequency characteristic H (ω) of the vibration means 1 is attenuated at 12 dB / octave, the flatness is obtained without the correction means 6. Frequency characteristics and a constant harmonic distortion rate.
[0016]
Specifically, when an ultrasonic wave having a resonance frequency ωC (for example, 40 KHz) is modulated by an audible sound (ωL = 20 Hz to ωH = 20 KHz), the modulated ultrasonic signal is converted into a center frequency ωC and an audible signal (ωL （ (ωC−ωH) to (ωC + ωH) in the frequency domain of the difference from the frequency band up to ωH, and is affected by the frequency characteristics of the vibration means 1 in this range. Therefore, as shown in FIG. 11, in the frequency range (ωC−ωH) to (ωC−ωL) lower than the resonance frequency ωC of the vibration means 1, it is proportional to the square of the frequency difference (ωC−ω) ² . In the frequency range (ωC + ωL) to (ωC + ωH) higher than the resonance frequency of the vibration means 1, if the vibration means 1 has a frequency characteristic inversely proportional to the square of the frequency difference (ωC−ω) ² , the nonlinear effect is generated. The characteristics of the audible sound generated are flattened, which is desirable.
[0017]
However, in reality, as shown in FIG. 12, the frequency characteristics of a general vibration unit 1 using a piezoelectric element are different from desired characteristics. In particular, near the resonance frequency ωC, the frequency peak has characteristics lower than desired characteristics. Therefore, the frequency characteristic of the correction means 6 is set as shown in FIG. 13 so that the characteristic of FIG. 12 becomes the ideal characteristic shown in FIG. Incidentally, the correction means 6 can be constituted by, for example, a digital filter.
FIG. 14 shows the output characteristics of the input body of the general vibration means 1. When the vibration means 1 having the input-output characteristic A shown in FIG. 14 is used, the input-output characteristic B of the correction means 6 is changed to a characteristic shown in FIG. 15 (a non-linear characteristic B opposite to the characteristic A shown in FIG. 14). 16), the input characteristics of the device and the output characteristics of the vibration means 1 can be linearized as shown by the solid line in FIG. As a result, it is possible to linearize the change in the sound pressure of the vibration transmitted from the vibration means 1 to the human body.
[0018]
In FIG. 7, the signal after modulation is corrected to correct the frequency characteristic and the input / output characteristic to desired characteristics. However, a configuration in which the input signal before modulation is corrected as shown in FIG. 17 is also effective. In this case, the sideband SUL ′ in which the sidebands SUL ′ of the sidebands SUL: SUH (see FIG. 18A) generated by the amplitude modulation and the frequency components ωC−ωL and ωC + ωL close to the resonance frequency ωC (assumed to be the same frequency as the carrier) ωC. And SUH ′, the frequency characteristic of the ultrasonic radiation of the vibration means 1 can be corrected from the curve B1 shown in FIG. 18A to B2. As a result, on the side of the vibration means 1 lower than the resonance frequency ωC, the characteristic can be corrected to a characteristic proportional to the square curve, and on the side higher than the resonance frequency ωC, the characteristic can be corrected to the characteristic inversely proportional to the square curve. For this purpose, the correction characteristic of the correction means 6 may be a low-frequency emphasis characteristic as shown in FIG. 18B.
[0019]
FIG. 19 shows still another embodiment. In this embodiment, a correcting means 6 is added to the embodiment shown in FIG. As a frequency correction characteristic of the correcting means 6, a signal input to the vibrating means 1 is corrected in advance in accordance with the frequency characteristic of the vibrating material 5 in addition to the frequency characteristic of the vibrating means 1, thereby providing a wide frequency characteristic. Audible vibration with flat characteristics can be given to the human body. Although FIG. 19 shows a case where the signal after modulation is corrected, it is also effective to correct the input signal before modulation as in the case of FIG.
[0020]
FIG. 20 shows still another embodiment of the present invention. In this embodiment, the signal input to the vibration means 1 is provided with an adding means 7 for obtaining a signal obtained by adding an audible signal to the amplitude-modulated non-audible signal shown in FIG.
The generation of an audible signal due to the non-audible vibration non-linear effect is a non-linear characteristic, which makes it very difficult to control sound quality. As in the embodiment shown in FIGS. 7 and 19, there is a case where the flattening can be performed by the correcting unit 6, but in some cases, depending on the characteristics of the vibrating unit 1, the correction cannot be performed by the correcting unit 6 alone. In this case, by mixing the audible signals, it is possible to transmit vibration to the human body in a form that supplements the audible signals generated by the nonlinear effect. Since the signal in the audible band is controlled only by the linear effect, the control is easier than in the non-audible band which is non-linear, and as a result, the control of the sound quality becomes easier.
[0021]
FIG. 21 shows still another embodiment of the present invention, in which the audible vibration and the non-audible modulated vibration are individually applied to the correcting means 6. The characteristics of the vibration means 1, the vibration material 5, and the human body have different frequency characteristics and input / output characteristics between the case of the audible vibration band and the case of the non-audible vibration band. Thus, finer sound quality control becomes possible. In FIG. 21, correction is performed on the non-audible signal after modulation, but it is also effective to correct the input signal before modulation as in FIG.
[0022]
【The invention's effect】
As described above, according to the present invention, the audible vibration can be efficiently transmitted to the human body by the vibration means for generating the audible vibration due to the non-audible vibration nonlinear effect inside the vibration material 5. In addition, non-audible vibration that causes nonlinear efficiency is not transmitted to the human body as much as possible, so that the nonlinear effect can be safely generated.
[Brief description of the drawings]
FIG. 1 is a block diagram for explaining an embodiment of a headphone device proposed in the present invention.
FIG. 2 is an exploded perspective view for explaining a configuration of a main part of the present invention.
FIG. 3 is an enlarged cross-sectional view for explaining the main part shown in FIG. 2 in further detail;
FIG. 4 is a graph showing measurement results for explaining a difference in demodulation effect caused by a difference in vibration material.
FIG. 5 is a perspective view for explaining a state in which the headphone device proposed in the present invention is worn on a human body.
FIG. 6 is a side view of FIG. 5;
FIG. 7 is a block diagram for explaining another embodiment of the headphone device proposed in the present invention.
FIG. 8 is a characteristic curve diagram for explaining a frequency characteristic of an audible sound generated by a non-linear effect of ultrasonic waves.
FIG. 9 is a characteristic curve diagram for explaining frequency characteristics of a general ultrasonic transducer.
FIG. 10 is a characteristic curve diagram showing an example of an equivalent low-frequency characteristic of the vibration means required to generate an audible sound having a flat frequency characteristic without frequency correction, and an amplitude frequency characteristic of the vibration means.
FIG. 11 is a characteristic curve diagram showing a frequency characteristic of a vibrating unit capable of generating an audible sound having a flat frequency characteristic without performing frequency correction.
FIG. 12 is a characteristic curve diagram for explaining actual frequency characteristics of the vibration means.
FIG. 13 is a characteristic curve diagram for explaining the correction characteristic of the correction unit for correcting the frequency characteristic of the vibration unit shown in FIG. 12 to the ideal frequency characteristic shown in FIG.
FIG. 14 is a characteristic curve diagram for explaining an example of the input-output characteristics of the vibration means.
FIG. 15 is a characteristic curve diagram for explaining a correction characteristic for linearly correcting the input versus output characteristic shown in FIG.
FIG. 16 is a characteristic curve diagram for explaining a result of correcting the input versus output characteristics of the vibration means shown in FIG. 14 with the correction characteristics shown in FIG. 15;
FIG. 17 is a block diagram for explaining a modified embodiment of the headphone device proposed in the present invention.
FIG. 18 is a characteristic curve diagram for explaining the correction characteristic of the embodiment shown in FIG.
FIG. 19 is a block diagram for explaining still another embodiment of the headphone device proposed in the present invention.
FIG. 20 is a block diagram for explaining still another embodiment of the headphone device proposed in the present invention.
FIG. 21 is a block diagram for explaining still another embodiment of the headphone device proposed in the present invention.
FIG. 22 is a block diagram for explaining a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vibration means 5 Vibration material 2 Ultrasonic signal generation means 6 Correction means 3 Input signal 7 Addition means 4 Amplitude modulation means

Claims (2)

Ultrasonic signal generating means for generating an ultrasonic signal of a frequency higher than at least the audible region,
Modulation means for amplitude-modulating the ultrasonic signal with an audio signal in an audible region to obtain a modulated signal,
Exciting means for generating non-audible vibration by the modulated signal,
A vibrating material made of either natural cartilage or regenerated cartilage having a non-linear characteristic between the contact acceleration and the amplitude of the sound output substantially equal to the acoustic impedance of the human body,
A housing for storing the vibration means with the vibration surface of the vibration means as a surface,
Headphone device provided with. Ultrasonic signal generating means for generating an ultrasonic signal of a frequency higher than at least the audible region,
Modulation means for amplitude-modulating the ultrasonic signal with an audio signal in an audible region to obtain a modulated signal,
Exciting means for generating non-audible vibration by the modulated signal,
A resin having a Young's modulus of 0.5 × 10 ^{6 to} 0.5 × 10 ⁸ Pa, which is in contact with the vibration means and has a nonlinear characteristic between contact acceleration and the amplitude of sound output which is substantially equal to the acoustic impedance of the human body. A vibration material composed of materials,
A housing for storing the vibration unit with the vibration surface of the vibration unit as a surface,
Headphone device provided with.

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