JP4548783B2 - headphone - Google Patents

Description

  The present invention relates to a headphone that transmits acoustic vibration to human hearing using a piezoelectric speaker that converts an acoustoelectric signal into acoustic vibration.

  In general, a headphone includes a speaker that converts an acoustoelectric signal into acoustic vibration, a housing that houses the speaker, and an ear pad that fits around the ear. As the speaker, an electromagnetic speaker using an electromagnetic force composed of a magnet and a coil is used. However, there is another speaker using a piezoelectric speaker using the inverse piezoelectric effect of piezoelectric ceramics.

  In general, a piezoelectric element called a piezoelectric unimorph having a structure in which a piezoelectric ceramic plate is bonded to a metal plate is used for a piezoelectric speaker. Piezoelectric speakers have the advantage of being thinner and lighter than electromagnetic speakers, but are not so often used because the sound pressure in the low frequency range is insufficient in the frequency characteristics of sound pressure.

  Some headphones that use piezoelectric speakers have acoustic speakers that generate inaudible bands or bone conduction acoustic vibrations as an auxiliary role for electromagnetic speakers. . Headphones using such bone conduction type speakers are disclosed in Patent Document 1 and Patent Document 2.

  In headphones using bone conduction speakers, for example, a vibrating body is set on the protruding part of the bone on the back side of the auricle (ear shell), and sound is transmitted to the auditory organ of the inner ear by bone conduction of the head. There are headphones that transmit and perceive. Acoustic vibrations emitted from headphones using normal air-conducting speakers are recognized by cochlear sensory cells through the ear canal, eardrum, ear ossicles, vestibule window, and the like. On the other hand, the acoustic vibration emitted from the headphones using the bone conduction speaker is directly transmitted to the auditory organ of the inner ear and recognized as sound. For this reason, headphones using bone conduction speakers transmit almost no ambient sound, so they are suitable for separating and perceiving surrounding sounds and conversational sounds to be heard even in high noise levels. It is considered as headphones. Such headphones are disclosed in Patent Document 3.

Japanese Patent Laid-Open No. 11-331972 JP 2003-032768 A JP 2003-018863 A

  However, compared with the air conduction sound perceived by the normal transmission path by the air conduction type speaker, the bone conduction sound by the bone conduction type speaker has problems such as unnatural sound quality and lack of clarity. In addition, bone conduction speakers are difficult to use as air-conducting speakers due to lack of sound radiation and insufficient low-frequency sound pressure in frequency characteristics. There is a disadvantage of not becoming. Further, when an electromagnetic speaker is used as a bone conduction speaker, there is a problem that efficiency is poor.

  Therefore, an object of the present invention is to solve the above-described problems in the prior art. Specifically, an object of the present invention is to provide a headphone that uses a single type of piezoelectric speaker that does not use an electromagnetic speaker in combination, the sound quality of bone conduction sound is natural and clear, and sufficient sound pressure in a low frequency range can be secured.

  According to the present invention, it is composed of a ring-shaped ear pad filled with fluid, a piezoelectric vibrator attached in close contact with the ear pad, and a diaphragm provided on a ring-shaped inner peripheral portion of the ear pad. Can be obtained.

  In the above configuration according to the present invention, the acoustic vibration generated by the conversion of the acoustoelectric signal by the piezoelectric vibrator is transmitted to the ear cartilage and the skull around the ear via the fluid filled in the ear pad, It is recognized by the auditory organ of the inner ear as a bone conduction sound. Further, the acoustic vibration also vibrates the diaphragm disposed on the ear pad through the fluid filled in the ear pad, and generates air conduction sound. Therefore, the headphone according to the present invention can transmit acoustic vibrations to the auditory organ by both air conduction sound and bone conduction sound even with a piezoelectric speaker alone.

  According to the invention, there is obtained a headphone characterized in that the piezoelectric vibrator is a piezoelectric bimorph or a piezoelectric unimorph.

  According to the present invention, it is possible to obtain a headphone characterized in that the fluid is liquid or gas.

  According to the present invention, it is possible to provide a headphone that uses a single type of piezoelectric speaker that is not used in combination with an electromagnetic speaker, the sound quality of bone conduction sound is natural and clear, and sufficient sound pressure in the low sound range can be secured. .

  Embodiments of headphones according to the present invention will be specifically described below with reference to the drawings.

  FIG. 1 is a diagram showing a main part of a headphone unit part of a headphone according to the present invention. Fig.1 (a) is a front view of the principal part of a headphone unit part, FIG.1 (b) is a figure which shows the (a)-(b) cross section shown to Fig.1 (a). As shown in FIG. 1A, the main part of the headphone unit 11 of the present invention has a structure in which a piezoelectric vibrator 2 is attached to the surface of a ring-shaped ear pad 1. A diaphragm 3 is provided on the inner periphery of the ring shape of the ear pad 1.

  As shown in FIG. 1B, the interior 4 of the ear pad 1 is filled with fluid. As the fluid to be filled, it is advantageous to use air in consideration of weight and cost. Further, since the sound propagation speed varies depending on the density of the medium, the response varies depending on the fluid used. For example, the propagation speed of sound in the air is about 350 m / second, whereas the propagation speed of sound in the water is about 1500 m / second, so that the response speed of water is about four times faster than air. Moreover, since the attenuation of the propagating sound is less in water than in air, water is better than air in terms of acoustic characteristics. The fluid to be used may be appropriately selected according to the application, and if necessary, a gas other than air, oil or liquid other than water, and the like may be used as the fluid. Further, it is preferable that the fluid is sufficiently charged so that the ear pad 1 does not give a sense of incongruity to the ear when the ear pad 1 is pressed against the ear.

  Moreover, although the material of the ear pad 1 uses a vinyl sheet or a synthetic leather, it is necessary that the fluid filled therein does not leak. You may perform waterproofing as needed. Further, since the surface of the ear pad 1 is in direct contact with the skin, care should be taken to select a material that is kind to the skin at least at the contact portion with the skin. In addition, the ring shape of the ear pad 1 does not need to be a complete annular shape. An oval shape or a polygonal shape may be used, and a shape that provides a good feeling when worn on the ear is desirable. The shape of the diaphragm 3 may be appropriately selected in accordance with the circular shape, the oval shape, the polygonal shape, the design, and the shape of the ear pad 1.

  With this configuration, when an acoustoelectric signal is input to the piezoelectric vibrator 2, the piezoelectric vibrator 2 vibrates. This vibration is transmitted from the portion of the piezoelectric vibrator 2 attached to the ear pad 1 to the fluid inside the ear pad 1 so that the entire ear pad 1 vibrates, and the vibration is also transmitted to the vibration plate 3. Vibrate. A piezoelectric speaker capable of conducting an acoustoelectric signal as acoustic vibration is obtained by the propagation action of the vibration.

  FIG. 2 is a diagram showing a state in which the headphones of the present invention are applied to the ear 5. In FIG. 2, only the main part of the headphone unit 11 is illustrated as in FIG. The acoustic vibration generated by the diaphragm 3 is transmitted to the ear 5 and is transmitted to the auditory nerve of the cochlea through the ear canal, the eardrum, the ossicle, and the vestibule window, and is perceived as a so-called air conduction sound. Further, when the ear pad 1 is used by being pressed around the ear 5, the acoustic vibration generated from the ear pad 1 is transmitted through the bone conduction path of the human head such as the cheekbone on the front side of the ear pinna or the cartilage behind the ear. The acoustic vibration is transmitted to the perception organ of the inner ear and is perceived as a so-called bone conduction sound.

  As described above, the headphone according to the present invention functions as both a speaker in which the same piezoelectric vibrator transmits vibration to the eardrum via the ear canal and a bone conduction speaker. Due to the function of emitting sound into the air and the function of generating bone conduction vibration, the sound signal is combined and recognized by the listener, so that a natural audible sensation from the low range to the high range can be realized.

  The headphone is completed by giving sound leakage prevention and holding function to the head to the main part of the headphone unit. FIG. 3 shows a cross-sectional view of the headphone unit 11. As shown in FIG. 3, one side of the ear pad 1 is covered with a housing 6 for preventing sound leakage to the outside, protecting the device, and the like. As shown in the drawing, when the soundproofing material 7 is provided inside the housing 6, the effect of preventing sound leakage to the outside is further improved. Further, a protective plate 9 having a through hole 8 for protecting the vibration plate 3 may be provided on the side opposite to the housing 6 as necessary.

  FIG. 4 is an external view showing an embodiment of the present invention. An example of headphones in which a spring-like band 10 for holding on the head is attached to a headphone unit 11 is shown. The headphone of the present invention listens to both air-conducted sound and bone-conducted sound. However, since the mounting method on the head is not particularly different from ordinary headphones, the holding mechanism on the head is conventional. What is used for the headphone of what. The acoustoelectric signal is transmitted to the piezoelectric element through the cable 12.

  FIG. 5 is a diagram showing a piezoelectric vibrator portion of the present invention. FIG. 5A is an enlarged front view of the piezoelectric vibrator portion 15 indicated by a broken-line circle in FIG. FIG.5 (b) is a figure which shows the (a)-(b) cross section shown to Fig.5 (a). In FIG. 5, the piezoelectric vibrator 2 is attached to the ear pad 1 by bonding the piezoelectric vibrator 2 with an adhesive on the outer surface of the sheet 13 covering the fluid filled in the inside 4 of the ear pad 1. Further, a protective sheet 14 is attached so as to cover the piezoelectric vibrator 2 to reinforce the piezoelectric vibrator 2 and its periphery. The attachment method of the piezoelectric vibrator is not limited to the above attachment method as long as the adhesion force between the piezoelectric vibrator and the ear pad and the vibration of the piezoelectric vibrator are sufficiently transmitted to the ear pad.

  As the piezoelectric vibrator, a piezoelectric bimorph in which a piezoelectric ceramic plate is attached to both surfaces of a single elastic plate, a piezoelectric unimorph in which a piezoelectric ceramic plate is bonded to only one surface of a single elastic plate, or the like may be used. In addition, a laminated piezoelectric vibrator having an internal electrode may be used. 5A shows a circular piezoelectric vibrator, a rectangular piezoelectric vibrator may be used. Furthermore, the piezoelectric vibrator is preferably covered with a flexible material in advance for the purpose of protecting itself and strengthening the adhesion to the sheet.

  Hereinafter, the headphones according to the present invention will be described in more detail using examples.

  In FIG. 3, the inside 4 of the ear pad 1 was filled with air. The ear pad 1 was made of a soft vinyl material having a thickness of 0.2 mm and a donut shape having an outer diameter of 70 mm and an inner diameter of 30 mm. The cross section of the ring-shaped portion filled with air is substantially square as shown in FIG. 5B, and the vertical and horizontal dimensions are 20 mm × 15 mm.

  Further, in FIG. 3, a diaphragm 3 having a diameter of 30 mm is provided on the inner diameter portion of the ring shape. Further, a protective plate 9 having the same diameter as that of the vibration plate 3 and having a number of holes having a diameter of 1 mm was disposed on a resin plate having a thickness of 1 mm. The piezoelectric vibrator 2 that generates acoustic vibrations is an epoxy-based piezoelectric ceramic disc having a diameter of 10 mm and a thickness of 0.15 mm, on which electrodes are formed on both surfaces of a metal plate having a diameter of 15 mm and a thickness of 0.1 mm. A piezoelectric bimorph bonded with an adhesive was used.

  A piezoelectric material manufactured by NEC TOKIN Co., Ltd. was used as the piezoelectric ceramic. The piezoelectric vibrator 2 was fixed to the ear pad 1 with an epoxy adhesive, and the piezoelectric vibrator 2 was covered with a rubber sheet with an adhesive to produce two headphone units 11. Furthermore, the headphone as shown in FIG. 4 was produced using the housing and the band that are used in commercially available headphones.

  FIG. 6 is a graph showing the acoustic characteristics of the headphones according to the present invention. For comparison, the acoustic characteristics of headphones using conventional electromagnetic bone conduction speakers are also shown. In the graph of FIG. 6, the horizontal axis represents the frequency of the acoustoelectric signal, and the vertical axis represents the vibration acceleration of the acoustic vibration propagated to the auditory nerve. This vibration acceleration indicates a value measured using a modeled artificial inner ear (Artificial Mastoid Type 4930 manufactured by B & K), and the magnitude of the vibration acceleration in the inner ear is the strength of the acoustic signal received by the auditory nerve. It is assumed to be proportional to the height. The vibration acceleration is displayed in decibels with 1 G (9.8 m / s2) as 0 dB.

  As can be seen from the graph of FIG. 6, the acoustic characteristics of the headphones according to the present invention are lower than the acoustic characteristics of headphones using a conventional electromagnetic bone conduction speaker, except for the frequency band from 500 Hz to 900 Hz. It has been confirmed that the vibration acceleration in the sound range is large, and there is no extreme peak frequency of the electromagnetic bone conduction speaker, and it is a flat characteristic. This characteristic indicates that the sound quality is natural and clear, and the sound pressure in the low sound range is sufficiently secured.

  The present invention can be used for a bone conduction application device in addition to headphones for an acoustic device, and can also be used for a medical acoustic device, an ultrasonic generator, and the like.

The figure which shows the principal part of the headphone unit part of an Example. FIG. 1A is a front view. FIG.1 (b) is sectional drawing. The figure which shows the state which applied the headphones of the Example to the ear | edge. Sectional drawing of the headphone unit of an Example. The external view which shows an Example. The figure which shows the piezoelectric vibrator part of an Example. FIG. 5A is a front view. FIG. 5B is a cross-sectional view. The graph which shows the acoustic characteristic of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ear pad 2 Piezoelectric vibrator 3 Diaphragm 4 Inside 5 Ear 6 Housing 7 Soundproof material 8 Through-hole 9 Protection plate 10 Band 11 Headphone unit 12 Cable 13 Sheet 14 Protection sheet 15 Piezoelectric vibrator part

Claims (3)

  A headphone comprising: a ring-shaped ear pad filled with a fluid therein; a piezoelectric vibrator attached in close contact with the ear pad; and a diaphragm provided on a ring-shaped inner periphery of the ear pad.   The headphone according to claim 1, wherein the piezoelectric vibrator is a piezoelectric bimorph or a piezoelectric unimorph.   The headphone according to claim 1, wherein the fluid is a gas or a liquid.

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