JPS6098797A - Piezo-electric electroacoustic transducer - Google Patents

Abstract

PURPOSE:To attenuate acoustic pressure at low frequency and to make easier to hear sound by providing the second acoustic leakage to leak sound produced by a piezo-electric vibrator, backward along an exhaust chamber board without passing the sound through the exhaust chamber. CONSTITUTION:A diaphragm 14 comprises a piezo-electric vibrator 15 which is bonded by a ceramic piezo-electric body 13 and a bonding agent. An exhaust chamber board 18 possesses the first acoustic leakage hole 20 which connects an exhaust chamber board 19 with atmosphere, and also possesses the second acoustic leakage hole 22 which connects an input terminal 21 and a front air chamber 17, and atmosphere. A vibrator 15 is furnished with a small hole 23 which makes a connection through the leakage hole. A case 16 holds a sound release hole 25. Thus separating the sound release 25 from the leakage hole 22 in the front air chamber 17 and selecting properly the hole 22 in size and numbers, then a sound level at low frequency is attenuated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electroacoustic transducer used in telephone receivers, etc., and in particular to a piezoelectric electroacoustic transducer using a piezoelectric vibrator as a transducer. It is.

Conventional Structures and Their Problems Piezoelectric vibrators in which a ceramic piezoelectric body is attached to a metal diaphragm have been widely used in piezoelectric electroacoustic transducers. If this piezoelectric vibrator is placed in a case with a front air chamber, a back air chamber, and a leak hole, the electroacoustic conversion effect can be made flat frequency characteristics from low frequencies to the required frequency band, and electromagnetic electroacoustic Compared to the IJS type transducer, it can be lighter in weight3. However, conventional piezoelectric electroacoustic transducers have flat frequency characteristics down to the lowest frequency that humans can produce, so they do not produce low-frequency hum sounds. There is an important problem in that it is not possible to hear the voice clearly when there is a mixture of sounds.

A conventional electromagnetic electroacoustic transducer is shown in FIG. 1 is a front air chamber, 2 is a diaphragm, 3 is a first back air chamber 1, 4 is a slit spacer, 5 is a link, 6 is a magnet, 7 is a coil, 8d is an inner ball, 9 is a second back air chamber, 1o is an insulating plate, 11 is a terminal,
Reference numeral 12 denotes a small hole 3 provided in the diaphragm 2. In this electromagnetic electroacoustic transducer, the small hole 12 provided in the diaphragm 2 attenuates low frequencies. However, in piezoelectric electroacoustic transducers, it is difficult to attenuate only the low frequency curvature by drilling holes in the diaphragm itself. In addition, in order to electrically attenuate low frequencies, coils, capacitors, and resistors are required, making it impossible to reduce the size and weight, and increasing costs.Purpose of the InventionThe present invention provides a piezoelectric electroacoustic The purpose of this device is to attenuate the sound pressure at low frequencies and make it easier to open up the sound.

Structure of the Invention In order to achieve the above-mentioned object, the present invention provides a leak hole in the front air chamber that allows the sound generated by the piezoelectric vibrator to leak directly into the atmosphere behind the back air chamber without passing through the back air chamber. The configuration is as follows. This configuration makes it possible to attenuate the sound pressure at low frequencies, making it possible to hear the voice clearly.

The low cut frequency can be determined by the size and number of leak holes.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 2 to 5. 13 is a ceramic piezoelectric body with silver baked on the west J side. Reference numeral 14 denotes a metal diaphragm which is bonded to the ceramic piezoelectric body 13 with an adhesive and is electrically connected at the same time, thereby constituting a piezoelectric vibrator 15. case 16
constitutes a front air chamber 17 between it and the piezoelectric vibrator 15,
The rounded case 16 is made of metal, and is electrically connected to the metal diaphragm 14 of the piezoelectric vibrator 15, and the case 16 itself serves as one input terminal. A back air chamber 19 is formed between the back air chamber 19 and the piezoelectric vibrator 15.The back air chamber plate 18 is a chamber plate that connects the back air chamber 19 and the atmosphere. The piezoelectric vibrator 15 has a second acoustic leakage hole 22 connecting the hole 20 and the input terminal 21 and the front air chamber 17 and the center. A 1-node wire 24 is soldered to the surface of the ceramic piezoelectric body 13, and the other end thereof is soldered to the input horn terminal 21.

In order to electrically isolate the input terminal 21 and the case 16, the back air chamber plate 18 is made of an insulator.The case 16 has a sound emitting hole 25. During measurement, a coupler, which is a sealed air chamber artificially imitating an ear, is used, but the sound emitted from the sound emission hole 26 enters only the coupler, does not leak into the atmosphere, and is sent to the second acoustic leakage hole. The audio output from 22 leaks only into the atmosphere and does not enter the coupler. In this way, the sound emission hole 26 and the second acoustic leakage hole 22 of the front air chamber 17 are separated by 111.
Furthermore, by appropriately selecting the size and number of the second acoustic leakage holes 22, the sound pressure level at low frequencies can be attenuated.

When the diameter of the second acoustic leakage hole 22 for low frequency attenuation is made smaller, the cut frequency moves to the lower frequency side and is gradually attenuated from the cut frequency, and when the diameter is increased, the cut frequency moves to the higher frequency side and the cut frequency is reduced. It also rises near the frequency. Furthermore, if the number of the 20th blind acoustic leak holes 22 is increased, the cut frequency moves to a higher frequency range, and the frequency near the cut frequency also rises.

FIG. 5 shows the frequency characteristics of the sound pressure level when the second acoustic leak hole 22 shown in the example is attached and when it is not attached.

The broken line indicates the characteristics without the acoustic leakage hole 22, and the solid line 75 indicates the characteristics with the acoustic leakage hole 22.

Effects of the Invention As explained above, the piezoelectric electroacoustic transducer of the present invention has a simple structure of attaching a second acoustic leak hole to the back air chamber plate, and reduces the sound pressure level at low frequencies. can do. Furthermore, since the structure is simple and small, there is no need to change the structure of the case, and there is no need to use other electronic components, which is advantageous in terms of cost. .

[Brief explanation of the drawings] Figure 1 is a sectional view of a conventional electromagnetic electroacoustic transducer for telephones.
FIG. 2 is a top view showing an embodiment of the piezoelectric electroacoustic transducer according to the present invention, FIG. 3 is a sectional view taken along line A-A', and FIG.
-B' sectional view and FIG. 6 show frequency characteristic diagrams of the sound pressure level when the second acoustic leakage hole of the present invention is provided and when it is not provided. 13... Ceramic piezoelectric body, 14... Vibration plate, 15... Piezoelectric vibrator, 16...
Case, 17...Front air chamber, 18...Back air chamber plate, 19...Back air chamber, 2゜...First acoustic leak hole , 21... Input terminal, 22...
...Second acoustic leak hole, 23...Small hole, 2
4...Lead wire, 25...Sound emission hole. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure

Claims (1)

[Claims] A piezoelectric vibrator made by bonding a ceramic piezoelectric body to a metal diaphragm is placed in a case that has a sound emission hole on the top surface so as to form a front air chamber between the top surface of the case and the top surface of the case. A back air chamber plate that forms a back air chamber between the piezoelectric vibrator and the piezoelectric vibrator is attached to the bottom, and a first acoustic leak hole that communicates with the back air chamber is provided in the back air chamber plate. A piezoelectric electro-acoustic transducer in which an air chamber plate is provided with a second acoustic leak hole that communicates with the front air chamber and leaks the sound generated by the piezoelectric vibrator to the rear of the back air chamber plate that passes through the back air chamber. .