JP2003284189A - Piezoelectric speaker system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric speaker system provided with a sound absorbing function being the sound shield performance by the mass law or over to one side of a speaker face. <P>SOLUTION: The sound absorbing function being the sound shield performance by the mass law or over is provided to one side of a piezoelectric speaker face by providing an energy conversion/consumption means for converting vibration energy into electric energy and consuming the electric energy to one side of the piezoelectric speaker. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric speaker system using a card type speaker and other piezoelectric speakers,
In particular, it relates to those with sound insulation performance on the back side.

[0002]

2. Description of the Related Art In recent years, piezoelectric devices capable of reproducing up to a low frequency range of several hundreds of Hz have been widely used along with the trend toward light, thin, short and compact audio equipment and voice synthesis equipment. The piezoelectric speaker has a structure in which (a) a piezoelectric vibrating body obtained by laminating a piezoelectric element on an aluminum disc is fixed to a dish-shaped metal frame provided with air circulation holes through a support ring made of foam plastic. There are known ones (dish type piezoelectric speaker) and (b) one having a structure in which a vibration plate made of a piezoelectric ceramic element is fixed to a rectangular lightweight resin frame via a damper (card type piezoelectric speaker).

[0003]

In the conventional piezoelectric speaker, both of the above (a) and (b), due to the structure, the same level of sound is generated from both sides of the diaphragm. The sound of the opposite phase generated from the back side becomes unnecessary reflection sound (noise) on the front side, which causes a decrease in sound pressure due to sound interference and disturbs the frequency characteristics to reproduce a clear sound. Cause to interfere.

In the electric type speaker, various types of sound absorbing materials are known in order to block unnecessary sound radiated to the back side of the speaker, but the sound absorbing material used is urethane. , A porous metal, a porous ceramic, or the like, which utilizes the sound insulation performance according to the mass law. Such a sound absorbing material not only cannot expect a sound absorbing effect in a piezoelectric speaker having a maximum diameter of about several cm and a thickness of about several mm, but also reduces the advantages of the piezoelectric speaker.
It cannot be used.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a piezoelectric speaker system having a sound absorbing function equal to or higher than the sound insulation performance by the mass law on one side of the speaker surface.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention is directed to one side of a piezoelectric diaphragm of a piezoelectric speaker, in which vibration energy is converted into electric energy and the electric energy is consumed. It is characterized in that a means is provided, and one side of the surface of the piezoelectric speaker is provided with a sound absorption function having a sound insulation performance of the mass law or higher.
With the above configuration, when an audio signal is applied to the piezoelectric diaphragm of the piezoelectric speaker system, necessary sound is radiated from one side thereof. Unwanted sound generated from the other side is converted into electric energy by the energy conversion / consumption means, and the electric energy is further converted into, for example, thermal energy or electromagnetic energy and consumed.

The energy conversion / consumption means is a piezoelectric film attached to one side of the piezoelectric vibrating plate via an elastic support, and electrical energy including at least a coil component and a resistance component electrically connected to the piezoelectric film. It is desirable to consist of a consumption circuit. With the above configuration, acoustic vibration energy generated from the piezoelectric diaphragm is converted into electric energy in the piezoelectric film, and converted into heat energy by the resistance component or the coil component in the electric energy consumption circuit, and consumed. By incorporating a coil component and a capacitor component other than the piezoelectric film in the electric energy consuming circuit, it is possible to select a frequency at which heat generation is maximum.

In the present invention, it is desirable that the parameters of the coil component or the coil component of the entire electric circuit including the piezoelectric film and the electric energy consuming circuit are variable.
When it is variable, it is possible to absorb only the sound in a specific frequency band.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram schematically showing the configuration of a card speaker system according to the present invention. In FIG. 1, reference numeral 1 denotes a known piezoelectric speaker, which is a plate-type piezoelectric speaker (for example, product numbers EFB-VH57A, EFB-VH46A, E manufactured by Matsushita Electronic Components Co., Ltd.).
FB-VH36A), card type piezoelectric speaker (for example,
Matsushita Communication Industrial Co., Ltd. product number WM-R30, WM-
Any of R57) may be used. In this piezoelectric speaker 1,
A sound signal is applied from the sound source amplifier 2, and basically, sound is generated from both front and back surfaces thereof.

According to the present invention, an energy converting / consuming means 3 is provided on the back surface side of the piezoelectric speaker 1. The energy conversion / consumption means 3 converts mechanical energy (vibration energy) based on sound generated from the piezoelectric speaker 1 into electric energy, and also converts the electric energy into heat energy or electromagnetic energy for consumption. It is a thing.

In the energy conversion / consumption means 3 as described above, (1) as a first embodiment, a piezoelectric material having a function of converting mechanical energy into electric energy and electric energy input from the piezoelectric material are provided. A polymer composed of a combination with a circuit to be consumed, or (2) as a second embodiment, a polymer having a function of converting mechanical energy into electric energy and a function of converting electric energy into heat energy and consuming it. Damping materials can be used.

The piezoelectric material (1) includes a ceramic piezoelectric material exhibiting a piezoelectric effect on vibration energy in the audible frequency band, a thin film piezoelectric material, an organic piezoelectric material represented by a polymer film, ceramics and a polymer. However, since the card-type piezoelectric speaker itself is small, in order to utilize high mechanical energy / electric energy conversion efficiency in a small volume, a piezoelectric film (for example, Fuji Ceramic Co., Ltd.) can be used. Manufactured) is preferable.

The polymer damping material (2) is, for example, a piezoelectric dispersion type organic composite damping material in which a needle-shaped organic dielectric or ferroelectric is dispersed in a non-piezoelectric polymer matrix. (Patent No. 3192400) can be used. In this damping material, the vibration energy applied from the piezoelectric speaker 1 is transmitted to the organic dielectric material or ferroelectric material dispersed in the non-piezoelectric polymer matrix, resulting in distortion of the dielectric material or ferroelectric material. Vibration energy is converted into electric energy by the electric conversion action, and the electric energy is consumed as Joule heat by the resistance. As a result, the noise radiated from the back surface of the piezoelectric speaker is absorbed.

FIG. 2 is a conceptual diagram showing a structure in which the energy converting / consuming means 3 is composed of a combination of a piezoelectric material and an electric energy consuming circuit. In the example of FIG. 2, a piezoelectric film 32 is provided as an example of a piezoelectric material on the back surface side of the piezoelectric speaker 1 with an elastic support material 31 interposed therebetween. The elastic supporting member 31 is provided with discrete holes for allowing the movement of air when the piezoelectric vibrating plate composed of the piezoelectric ceramic element constituting the piezoelectric speaker 1 is vibrated by the audio signal applied from the sound source amplifier 2. Has been.

The electric energy consumption circuit 33 consumes electric energy generated by the piezoelectric film 32 by sound pressure, for example, by converting it into heat energy by a resistance element or by converting it into electromagnetic energy by a coil. Therefore, the electric energy consumption circuit 33 can be configured by an electric circuit having a resistance component, a coil component, and a capacitor component.

FIG. 3 is an equivalent circuit of the entire electric circuit including the piezo film 32 and the electric energy consuming circuit 33 of FIG. 2, and constitutes a series resonance circuit including R, L and C. In such a circuit, the frequency at which the current flowing through the resistor R becomes maximum depends on the coil component L or the capacitor component C of the entire electric circuit including the piezo film 32. That is, at the resonance frequency, the value of the current flowing through this circuit is maximized, and at the same time, the power consumed as heat energy in the resistor R is maximized.

The above “acoustic energy → electrical energy →
When viewed in the whole process of "thermal energy", the parameters that determine the frequency band in which the final thermal energy is likely to become are (a) the polarization frequency of the piezo film, (b) the coil component of the piezo film and the electric energy consumption circuit, ( c) Three components, the piezo film and the capacitor component of the electric energy consuming circuit. Therefore, by changing the parameters such as the polarization frequency of the piezo film and the coil component and the capacitor component of the entire electric circuit of the energy conversion / consumption means, it is possible to absorb sound in a specific frequency band.

The electric energy consumption circuit 33 is not limited to the one that consumes electric energy as Joule heat by converting it into thermal energy as described above and consumes electric energy of other types such as electromagnetic energy or light energy. It may be converted to and consumed.

[0019]

As described above, in the piezoelectric speaker system according to the present invention, one surface of the piezoelectric speaker is provided with the energy conversion / consumption means for converting vibration energy into electric energy and consuming the electric energy.
It is possible to provide a piezoelectric speaker system having a sound absorbing function that exceeds the sound insulation performance according to the mass law on one side of the speaker surface. Since the sound generated from one surface of the piezoelectric speaker is absorbed, a clear sound without noise is radiated from the other surface of the piezoelectric speaker.

The energy conversion / consumption means has a piezoelectric film attached to one side of the piezoelectric vibrating plate via an elastic support, and electrical energy including at least a coil component and a resistance component electrically connected to the piezoelectric film. In the case of the consumption circuit, the frequency at which heat generation is maximum can be selected by incorporating a coil component and a capacitor component other than the piezoelectric film in the energy consumption circuit.

According to the third aspect of the present invention, it is possible to absorb sound in a specific frequency band by setting / changing parameters such as the coil component of the entire electric circuit including the piezoelectric film.

The present invention is an automatic noise controller (ANC).
When used as a control speaker, the anti-phase sound with respect to the control signal is not generated, which can contribute to improvement in efficiency of the ANC system and simplification of control.

Further, since the piezoelectric speaker system according to the present invention is small in size as a whole, it is suitable for use in a speaker which requires space-saving and efficient radiation sound.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a basic configuration of the present invention.

FIG. 2 is a conceptual diagram showing one embodiment of the present invention.

FIG. 3 is an equivalent circuit of the embodiment of FIG.

[Explanation of symbols]

1 Piezoelectric speaker S sound 2 sound source amplifier 3 Electric energy conversion / consumption means 31 Elastic support 32 Piezo film (piezoelectric material) 33 Electric energy consumption circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Naoto Tagawa             38-8, Hikarimachi, Kokubunji, Tokyo 38 Foundation             Corporate Railway Technical Research Institute F-term (reference) 5D004 AA00

Claims (4)

[Claims] 1. A piezoelectric speaker of a piezoelectric speaker is provided with energy conversion / consumption means for converting vibration energy into electric energy and consuming the electric energy on one side thereof, and sound insulation by mass law is provided on one side of the piezoelectric speaker surface. A piezoelectric speaker system characterized by having a sound absorption function that exceeds performance. 2. The energy conversion / consumption means includes a piezo film attached to one side of a piezoelectric diaphragm via an elastic support, and at least a coil component and a resistance component electrically connected to the piezo film. The piezoelectric speaker system according to claim 1, comprising an electric energy consuming circuit including the electric energy consuming circuit. 3. The piezoelectric speaker system according to claim 2, wherein parameters such as a capacitor component or a coil component of the entire electric circuit including the piezoelectric film and the electric energy consuming circuit are variable. 4. The energy conversion / consumption means is a polymer vibration damping material having a function of converting mechanical energy into electric energy and a function of converting electric energy into heat energy and consuming it. The piezoelectric speaker system according to item 1.