JP4963979B2 - headphone - Google Patents

Description

  The present invention relates to a headphone capable of reducing the sound pressure of noise entering from the outside.

  With the spread of portable music players, headphones for personally listening to musical sounds have also become widespread. Portable music players are often used in streets with high noise levels and in vehicles such as trains and buses, and external noises can be heard through headphones as well as music played by the player. When listening to music in the noise, the music may be drowned out by external noise, so the user tries to listen to the music by raising the volume, and the volume increases too much, and the sound leaks from the headphones to the surrounding people. May cause unpleasant feelings. In addition, even when high-quality musical sounds are reproduced with headphones, noise entering from the outside affects the musical sounds, which may reduce the quality of reproduced sounds that can be heard by the user.

  Therefore, noise canceling headphones that are designed to cancel noise entering from the outside and reduce the sound pressure of the noise so that only the musical sound can be heard by the user's ears are becoming widespread. The principle of the noise-canceling headphones is that the noise entering the headphones is detected by a microphone, cancellation noise having a phase opposite to that of the detected noise signal is generated, and the noise is canceled by the cancellation noise. A typical noise-canceling headphone has one speaker and thus one voice coil. The noise signal collected by the microphone and converted into an electrical signal is further passed through a filter and delay circuit to generate a noise cancellation signal with a phase opposite to that of the noise signal, and this noise cancellation signal and the target music signal are synthesized (added). ) Is then amplified and input to one voice coil of the one speaker.

The sound output from the speaker is the result of converting the combined signal of the noise cancellation signal and the musical sound signal into sound, and the sound converted from the noise cancellation signal cancels all or part of the external noise entering the headphones. The sound that enters the user's ear is almost only the sound converted from the musical sound signal.
Alternatively, there is also a method in which the noise cancellation signal and the tone signal are individually amplified and then the noise cancellation signal and the tone signal are combined, and the one voice coil is driven by the combined signal. However, since the two power amplifiers are connected to the voice coil in series or in parallel, there is a problem that the two power amplifiers become loads with each other.

  FIG. 2 shows an example of a conventional noise cancellation type headphone. In FIG. 2, a flange member 2 is coupled to an open end of a bottomed tubular headphone housing 1, and a head pad 3 is fixed to the outer surface (left side in FIG. 2) of the flange member 2. . When the user uses the headphones, the outer end surface of the head pad 3 hits the user's head side surface, and the user's ear 13 is positioned in the space surrounded by the head pad 3. The flange member 2 has a window hole in the center and is formed in a ring shape. A headphone unit 5 is fixed to the inner surface (right surface in FIG. 2) of the flange member 2 so as to close the window hole. Yes. The headphone unit 5 includes a flat petri dish-like base 6, a petri dish-like yoke 7 that is smaller in diameter and flatter than the base 6 and is fitted to the inner bottom of the base 6, and a flat that is fixed to the center of the inner bottom of the yoke 7. And a plate-shaped pole piece 9 fixed to the front end face of the magnet 8, a voice coil 10 wound in a cylindrical shape, and a dome-shaped diaphragm 12.

  The open end face of the petri dish-shaped yoke 7 and the end face of the pole piece 9 are substantially in the same plane, and a ring shape is formed between the outer peripheral face of the pole piece 9 and the inner peripheral face of the open end side of the yoke 7. The voice coil 10 has entered the gap. A magnetic field using the magnet 8 as a source is formed in the ring-shaped gap, and the voice coil 10 exists in this magnetic field. The diaphragm 12 is formed with an arch-shaped edge portion surrounding a dome portion at the center, and the outer periphery of the edge portion is fixed to the base 6 so that the diaphragm 12 is supported so as to vibrate in the front-rear direction. One end of the voice coil 10 is fixed to the boundary between the central dome portion and the edge portion of the diaphragm 12, and the voice coil 10 is supported so as not to contact the yoke 7 and the pole piece 9. A musical tone signal is input to the voice coil 10 from a power amplifier (driver) of an external player, and the voice coil 10 is driven back and forth in accordance with the musical tone signal. It is done. This sound reaches the user's ear 13 surrounded by the head pad 3 through the central window hole of the flange member 2.

  The above description is a description of a general headphone. In the noise canceling type headphone, a microphone for detecting ambient noise and a noise canceling signal having a phase opposite to that of the noise detected by the microphone are generated in the above configuration. A signal processing circuit such as a synthesis circuit for synthesizing (adding) the generated noise cancellation signal with the musical tone signal and inputting the resultant signal to the voice coil 10 is added. Various ideas are applied to the position of the microphone and the configuration of the signal processing circuit. In FIG. 2, M1 to M4 show various examples of arrangement positions of noise detection microphones. M1 is an example in which the microphone is arranged inside the headphone, and is an example in which the front side of the microphone is arranged in the space immediately before the diaphragm 12 so as to face the outside of the headphone (left side in FIG. 2). M2 to M4 are examples in which microphones are arranged outside the headphones, M2 is an example in which the microphones are arranged on the upper part of the flange member 2, M3 is arranged in the lower part of the flange members 2, and M4 is arranged on the outer surface of the housing 1.

  In the noise-canceling headphones, various ideas have been made to cancel external noise more effectively. For example, in the headphones described in Patent Document 1, a small cavity is provided between a diaphragm (speaker diaphragm) and the ear canal in order to reduce noise while having a relatively constant frequency response, and the diaphragm is provided in the cavity. A microphone is arranged in the vicinity of the microphone, and a feedback signal based on the output of the microphone is coupled to an input electric signal reproduced by the headphones, and the combined signal is amplified to drive the diaphragm. In the conventional example shown in FIG. 2, a microphone is arranged at a position indicated by reference numeral M1.

In Patent Document 2, in order to enhance the noise canceling effect, a synthesized sound near the outer ear is picked up by a microphone, the synthesized sound is phase-inverted, and the phase-reversed audio signal and the tone signal from the sound source are the first. An invention relating to an active noise eraser configured to add by an adder circuit, add a musical tone signal from a sound source to the addition result by a second adder circuit, amplify the addition result and output the result from the speaker to the vicinity of the ear canal is described. Has been.
Patent Document 3 describes a headphone device in which a microphone unit is disposed via a vibration isolation member in a headphone unit used for an active noise control headphone in order to enhance a noise canceling effect.
Although the inventions described in Patent Documents 1 and 2 and the invention described in Patent Document 3 are aimed at improving the performance of the noise-canceling headphones, the object of the present invention described later cannot be achieved. Also, the technical idea is different.

  As known inventions related to the present invention, an active noise reduction signal processing path for reducing active noise, a talk through signal processing path for providing a talk through function, an active noise reduction signal processing path, and a talk through signal processing path are provided. A noise reduction headset including a switching element for disabling one or both has been proposed (see Patent Document 4). Patent Document 4 describes that the switching element disables the noise reduction signal path when the power supplied to the switching element is insufficient to operate the noise reduction signal path. In this respect, although it relates to a part of the effects of the present invention described later, the means for solving the problem is completely different from the present invention.

JP-A-6-343195 JP-A-9-54592 Japanese Utility Model Publication No. 5-36991 JP 2006-14307 A

An object of the present invention is to eliminate the problems of the conventional noise canceling headphones. That is, in the conventional noise cancellation headphones, the signal for canceling the noise and the musical sound signal are electrically combined and combined and pass through the signal processing circuit, so that the musical sound signal is affected by the noise cancellation signal and the sound quality is improved. to degrade. In addition, when the noise cancellation operation is performed, the sound quality difference occurs between the case where the noise cancellation operation is performed and the case where the noise cancellation operation is not performed.
Further, since the conventional noise canceling headphones have a built-in power supply battery for noise canceling operation, there are problems that the weight of the headphones becomes heavy, and noise canceling cannot be performed when the power supply battery is exhausted.

The present invention reduces the influence of the noise cancellation signal on the musical tone signal by reducing the electrical coupling relationship including the magnetic coupling and the electrostatic coupling between the noise cancellation signal and the musical tone signal as much as possible. It is an object of the present invention to provide a noise canceling type headphone with good sound quality, in which the power amplifying circuit and the power amplifying circuit for the musical sound signal do not load each other.
The present invention also enables noise cancellation without using a built-in battery, and eliminates the problems of heavy weight and noise cancellation that cannot be performed due to battery consumption, as in the prior art. The purpose is to provide.

The present invention includes a speaker unit which is driven by a tone signal, in headphones is provided with a power generator for generating power in accordance with background noise, and a piezoelectric element for driving the frame of the speaker unit by the signal generated by the power generating body The most important feature of the power generator is that it is composed of a second piezoelectric element different from the piezoelectric element .

  The speaker unit reproduces only a musical sound signal input from a sound source such as a player. The power generator generates power in accordance with the surrounding noise, and drives the piezoelectric element by this power generation signal. The frame of the speaker unit is mechanically vibrated by driving the piezoelectric element. If the sound generated by this mechanical vibration is in the opposite phase to the noise entering the headphones, the noise entering the headphones can be canceled, It is possible to transmit a reproduced sound of a musical sound signal with no noise or low noise.

A speaker unit driven by a piezoelectric element for noise cancellation and a musical tone signal is equivalent to being mechanically connected in series by a frame of the speaker unit. Since the diaphragm of the speaker unit has a structure that moves extremely easily, the acoustic mechanical impedance of the speaker unit is low. On the other hand, the piezoelectric element is made of, for example, piezoelectric ceramic, and the material itself is hard and difficult to move, and has high acoustic mechanical impedance. Therefore, it has an equivalent structure in which a speaker unit is mechanically coupled in series to a piezoelectric element having high acousto-mechanical impedance.
On the other hand, since the electrical drive system of the speaker unit and the electrical drive system of the piezoelectric element are electrically separated and the electrical coupling is shallow, the musical sound signal is less affected by the noise canceling signal and has high sound quality. Can play music signals.

Since the piezoelectric element for noise cancellation is driven by a power generation signal from a power generator according to the surrounding noise, a power source for noise cancellation operation is not required. Therefore, it is not necessary to incorporate a power supply battery for noise cancellation in the headphones, the headphone can be reduced in weight, and the problem that the noise cancellation operation cannot be performed due to battery consumption is eliminated.
If the sound insulation effect of the headphones is enhanced, the driving force of the piezoelectric element for canceling the noise may be small, and therefore the output of the power generator may be small.

  An embodiment of a headphone according to the present invention will be described below with reference to FIG. The same reference numerals are given to the same components as those of the conventional headphones shown in FIG.

  In FIG. 1, a tubular headphone housing 20 has a partition wall 21 at an intermediate portion in the axial direction, and the front side (left side in FIG. 1) and the rear side of the partition wall 21 are cylindrical portions 22 and 24, respectively. The headphone unit 5 is incorporated in the front cylinder portion 22, and the power generation body 32 that generates power according to the surrounding noise is incorporated in the rear cylinder portion 24. A ring-shaped head pad 3 is fixed to the open end of the front cylindrical portion 22. When the user uses the headphones, the outer end surface of the head pad 3 hits the user's head side surface, and the user's ear 13 is positioned in the space surrounded by the head pad 3.

  A headphone unit 5 is fixed inside the headphone housing 20 via a ring-shaped support 35. The headphone unit 5 includes a flat petri dish-shaped frame 6, a petri dish-shaped yoke 7 that is smaller in diameter and flatter than the frame 6 and is fitted to the inner bottom of the frame 6, and a flat that is fixed to the center of the inner bottom of the yoke 7. A magnet 8, a plate-shaped pole piece 9 fixed to the end face of the magnet 8, a voice coil 10 wound in a cylindrical shape, and a dome-shaped diaphragm 12. The front end surface (left end in FIG. 1) of the frame 6 of the headphone unit 5 has a circular shape, and the inner peripheral rear end surface of the support 35 is joined to the front end surface by bonding or the like. The cross-sectional shape of the support 35 is an arch shape, and the outer peripheral surface of the support 35 is fixed to the inner peripheral surface of the headphone housing 20 by bonding or other appropriate means. The support 35 is made of a material that is flexible and difficult to pass sound waves so as to allow the headphone unit 5 to move in the front-rear direction with respect to the headphone housing 20 by expansion and contraction of the piezoelectric element 30 described later. Yes.

  The open end surface of the petri dish-shaped yoke 7 and the end surface of the pole piece 9 are substantially flush with each other, and a ring-shaped gap is formed between the outer peripheral surface of the pole piece 9 and the inner peripheral surface of the open end side of the yoke 7. The voice coil 10 enters the gap. A magnetic field using the magnet 8 as a source is formed in the ring-shaped gap, and a voice coil 10 in which a thin conductive wire is wound in a cylindrical shape exists in the magnetic field. The diaphragm 12 is formed with an arch-shaped edge portion surrounding a dome portion at the center, and the outer periphery of the edge portion is fixed to the frame 6 so that the diaphragm 12 is supported so as to vibrate in the front-rear direction. One end in the axial direction of the cylindrical voice coil 10 is cantilevered at the boundary between the central dome portion and the edge portion of the diaphragm 12 so that the voice coil 10 does not contact the yoke 7 or the pole piece 9. It is supported by the diaphragm 12. When a musical tone signal is input to the voice coil 10 from a power amplifier (driver) of an external player, the voice coil 10 is driven back and forth in accordance with the musical tone signal, and the diaphragm 12 vibrates accordingly. Is emitted. The headphone unit 5 is disposed with the diaphragm 12 facing the open end of the tube portion 22 of the headphone housing 20 so that the sound reaches the user's ear 13 surrounded by the head pad 3.

One surface of the piezoelectric element 30 is fixed to the front surface side (left surface side in FIG. 1) of the frame 6 of the speaker unit 5 and the partition wall 21 of the headphone housing 20, and one surface of the elastic sheet 40 is fixed to the other surface of the piezoelectric element 30. Is fixed, and the other surface of the elastic sheet 40 is fixed to the rear end surface of the frame 6 of the speaker unit 5. In other words, the speaker unit 5 has the frame 6 coupled to the headphone housing 20 with the elastic sheet 40 and the piezoelectric element 30 interposed therebetween. More specifically, the piezoelectric element 30 is disposed between the frame 6 of the speaker unit 5 and the headphone housing 20, one surface side of the piezoelectric element 30 is coupled to the frame 6, and the other surface side of the piezoelectric element 30 is headphone. Further , an elastic sheet 40 that is coupled to the housing 20 side and functions as a mechanical filter is interposed between the other surface side of the piezoelectric element 30 and the frame 6. The partition plate 21 and the piezoelectric element 30, the piezoelectric element 30 and the elastic sheet 40, and the elastic sheet 40 and the frame 6 are fixed by, for example, bonding.

One feature of the embodiment of the headphone according to the present invention is that it includes the piezoelectric element 30 and a second piezoelectric element 32 that generates a signal applied to the piezoelectric element 30. The second piezoelectric element 32 has a center hole formed in a ring-shaped support wall 26 that is integrally formed in parallel with the partition plate 21 from the inner peripheral surface of the rear cylinder portion 24 of the headphone housing 20 inward in the radial direction. It is fixed so as to block. The second piezoelectric element 32 constitutes a power generation body that generates electric power according to surrounding noise, and a sound receiving member 36 is fixed to one surface side (the right outer surface side in FIG. 1). The sound receiving member 36 collects noise around the headphones, vibrates according to the noise, and has a function of transmitting this vibration to the second piezoelectric element 32 so that this function can be effectively exhibited. It is made of a material that easily vibrates in response to noise, that is, a material that is light in mass and rigid. The sound receiving member 36 has a conical sound receiving portion, and the area of the sound receiving portion is larger than the area of the surface facing the sound receiving portion of the second piezoelectric element 32. It is devised so that the vibration is concentrated and transmitted to the second piezoelectric element 32. In the example shown in FIG. 1, the sound receiving member 36 is formed in a flat truncated cone shape, and the flat surface at the top of the truncated cone shape is fixed to the second piezoelectric element 32. The illustrated sound receiving member 36 is a member obtained by molding a plate-like member into a truncated cone shape. However, a material having a light mass, for example, a foamed resin may be integrally formed. The sound receiving member 36 receives the ambient noise and can vibrate relative to the headphone housing 20, so that the outer periphery of the sound receiving member 36 is inside the tube portion 24 of the headphone housing 20 via a flexible edge member 38. It is connected to the peripheral surface.

  The power generation output by the second piezoelectric element 32 is electrically connected so as to be applied to the piezoelectric element 30. The piezoelectric element 30 is a commonly used piezoelectric element, and vibrates (expands and contracts) in the axial direction of the headphone housing 20 when the power generation output of the second piezoelectric element 32 is applied. The second power generating element 32 is preferably one that can generate power by vibration of air, and therefore has a low mechanical impedance. For example, a piezoelectric bimorph may be used. The piezoelectric element 30 is mechanically vibrated by being driven by the power generation signal of the second piezoelectric element 32 and drives the frame 6 of the speaker unit 5. The support 35 is mechanically vibrated when the piezoelectric element 30 is driven, so that a material that allows mechanical vibration of the frame 6 of the speaker unit 5 relative to the headphone housing 20 is selected and formed in an arch shape in cross section. Has been. When the support 35 allows the frame 6 to vibrate, the entire speaker unit 5 is driven by the piezoelectric element 30 and vibrates.

  According to the embodiment described above, the speaker unit 5 is driven by a musical sound signal input from a player or the like to reproduce a musical sound. The piezoelectric element 30 receives the output signal of the second piezoelectric element 32 as a power generator that generates power in accordance with ambient noise, that is, the noise signal, and is driven and vibrated by the noise signal. The whole vibrates. This vibration is generated by driving the piezoelectric element 30 because the piezoelectric element 30 and the second piezoelectric element 32 are electrically connected so as to have an opposite phase to the noise entering the headphones. All or part of the noise entering the headphones is canceled out, and only the musical sound reaches the user's ear or the noise level is lowered.

  The piezoelectric element 30 driven by the noise cancellation signal and the speaker unit 5 driven by the tone signal are equivalent to being mechanically connected in series by the frame 6 of the speaker unit 5. Since the diaphragm 12 of the speaker unit 5 has a structure that is extremely easy to move, the acoustic mechanical impedance of the speaker unit 5 is low. On the other hand, the piezoelectric element 30 is made of, for example, piezoelectric ceramic, and the material itself is hard and difficult to move, and has high acoustic mechanical impedance. Therefore, the structure is equivalent to the case where the speaker unit 5 is mechanically coupled in series to the piezoelectric element 30 having high acousto-mechanical impedance, and the movement of the diaphragm 12 as viewed from the headphone housing 20 depends on the tone signal. The amplitude is large at the moment when the direction of vibration coincides with the direction of vibration by the piezoelectric element 30, and the amplitude is small if the directions of both vibrations are opposite to each other. That is, the movement of the diaphragm 12 of the speaker unit 5 by the piezoelectric element 30 and the movement of the diaphragm 12 by the driving of the speaker unit 5 are mechanically overlapped in series. By configuring so that the phase and the phase of the sound component generated by driving the piezoelectric element 30 are reversed, noise entering the headphones is canceled by driving the piezoelectric element 30.

In the embodiment shown in FIG. 1, the acoustic impedance, sound pressure, voltage, etc. of each part are defined as follows.
P ₁ : Sound pressure of noise component P _L : Sound pressure of noise component entering inside the headphones F ₁ : Force received by the sound receiving member 36 due to the noise component S ₁ : Sound receiving area of the sound receiving member 36 ZP _Z1 : Second piezoelectric Impedance X _{1 of} element 32: Amount of movement of second piezoelectric element 32 due to F ₁ e ₁ : Generated voltage of second piezoelectric element 32

The amount of force F ₁ received by the sound receiving member 36 due to the noise component is:
F ₁ = S ₁ · P ₁
It is. The amount _{X 1} of the second piezoelectric element 32 is moved by the force _{F 1} is
X ₁ = (1 / jω) (F ₁ / ZP _Z1 )
It is. By the second piezoelectric element 32 is moved by _{X 1,} the voltage _{e 1} of the second piezoelectric element 32 is power generation,
e ₁ = AX ₁ (A is a constant)
It becomes.

  Since the frequency component of the noise that leaks between the ear pad 3 and the human body and reaches the ear is in a low frequency region, in the illustrated embodiment, between the piezoelectric element 30 for noise cancellation and the frame 6 of the speaker unit. The elastic sheet 40 is interposed between the two. The elastic sheet 40 functions as a mechanical low-pass filter or high-cut filter that mechanically connects the piezoelectric element 30 and the frame 6 of the speaker unit, and effectively removes or reduces noise in a low frequency region effective for noise cancellation. can do.

As described above, according to the embodiment of the present invention, the electrical drive system based on the musical tone signal of the speaker unit 5 and the electrical drive system of the piezoelectric element 30 for noise cancellation are electrically separated. Since the electrical coupling is shallow, the musical sound signal is less affected by the noise cancellation signal, and the musical sound signal can be reproduced with high sound quality.
Since the signal applied to the piezoelectric element 30 for noise cancellation is an output signal of the second piezoelectric element 32 that generates power in response to ambient noise, noise cancellation is possible without requiring a power supply battery for noise cancellation operation. Lightweight headphones can be achieved.
The sound receiving member 36 has a conical sound receiving portion. The area of the sound receiving portion is larger than the area of the second piezoelectric element 32, and the vibration of the sound receiving member 36 is concentrated and transmitted to the second piezoelectric element 32. Thus, the second piezoelectric element 32 can efficiently generate a signal for canceling ambient noise.

It is a longitudinal cross-sectional view which shows the Example of the headphones which concern on this invention. It is a longitudinal cross-sectional view which shows the example of the conventional headphones.

Explanation of symbols

5 Speaker unit 6 Frame 10 Voice coil 12 Diaphragm 20 Headphone housing 30 Piezoelectric element 32 Second piezoelectric element 35 Support body 36 Sound receiving member 40 Elastic filter

Claims (7)

A speaker unit driven by a musical sound signal;
A generator that generates electricity according to the surrounding noise;
A piezoelectric element that drives a frame of a speaker unit by a signal generated by the power generator,
The power generator is a headphone comprising a second piezoelectric element different from the piezoelectric element.   The headphone according to claim 1, wherein a piezoelectric element is disposed between the frame and a headphone housing, one surface side of the piezoelectric element is coupled to the housing side, and the other surface side of the piezoelectric element is coupled to the frame.   The headphone according to claim 2, wherein an elastic sheet functioning as a mechanical filter is interposed between the other surface side of the piezoelectric element and the frame. The headphone according to any one of claims 2 to 3, wherein the frame is coupled to the headphone housing by a support that hardly allows sound waves to pass through.   The headphone according to claim 4, wherein the support allows vibration of the frame relative to the headphone housing by driving the piezoelectric element. A sound receiving member that vibrates in accordance with ambient noise is fixed to one surface of the second piezoelectric element, and the other surface of the second piezoelectric element is substantially integrally fixed to the headphone housing, and the sound receiving member vibrates according to the vibration of the sound receiving member. Headphones according to any one of claims 2 to 5 second piezoelectric element to generate electric power.   The sound receiving member has a conical sound receiving portion, and the area of the sound receiving portion is larger than the area of the second piezoelectric element, and vibration of the sound receiving member is concentrated and transmitted to the second piezoelectric element. The headphone according to claim 6.

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