JP2008199266A - Electroacoustic transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroacoustic transducer which allows piezoelectric acoustic components to be miniaturized furthermore and is capable of effectively generating sounds having frequencies lower than a resonance frequency of a front air chamber without attenuation. <P>SOLUTION: In the electroacoustic transducer wherein a piezoelectric acoustic component including a piezoelectric diaphragm 30 is surface-mounted on a circuit board 10, a sound output hole of the piezoelectric acoustic component 20 is formed in a face of a case, which doesn't face the circuit board 10, and an open hole 29 is formed in a face of the case, which faces the circuit board, and a through hole 13 is formed in a part of the circuit board corresponding to the open hole 29. A higher sound pressure can be obtained in comparison with sounding at the resonance frequency of the front air chamber when the piezoelectric diaphragm is operated at a frequency or its neighboring frequencies, lower than the resonance frequency of the front air chamber, and sounds emitted from the sound output hole 28 can be prevented from being attenuated by sounds emitted from the open hole 29. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an electroacoustic transducer formed by surface-mounting a piezoelectric acoustic component such as a piezoelectric buzzer or a piezoelectric sounder on a circuit board.

Conventionally, piezoelectric acoustic parts such as buzzers and sounders are widely used as sounding parts for generating alarm sounds and operation sounds in electronic devices, home appliances, mobile phones and the like. This type of piezoelectric acoustic component has a piezoelectric diaphragm attached to the inside of the case, and forms a sound emitting hole that emits sound into one room (front air chamber) of the case partitioned by the diaphragm. In the other chamber (rear air chamber), an open hole (or leak hole) for adjusting frequency characteristics is formed.

In recent years, with the miniaturization of devices and the high integration of electronic components, surface mounting of piezoelectric acoustic components on a circuit board is generally performed. When a piezoelectric acoustic component is surface-mounted on a circuit board, an open hole is formed on the side wall of the case so that the open hole provided on the back side of the case is not closed by the circuit board.

7 and 8 show an example of the surface mount type piezoelectric acoustic component A disclosed in Patent Document 1. FIG. The case 1 of the piezoelectric acoustic component A is composed of a case body 1a and a cover 1b. A piezoelectric diaphragm 2 is accommodated in the case 1, and the inside of the case 1 is separated from the front air chamber 3 and the rear by the piezoelectric diaphragm 2. The air chamber 4 is partitioned. The cover 1b has a sound emitting hole 5 that communicates with the front air chamber 3, and an opening hole 6 that communicates with the rear air chamber 4 is formed on the side wall near the bottom surface of the case body 1a. Furthermore, external connection terminal electrodes 7 and 8 are formed on the opposite side walls of the case body 1a for connection to the circuit board. When such a piezoelectric acoustic component A is surface-mounted on the circuit board B, the opening hole 6 is not closed by the circuit board, so that the effect of adjusting the frequency characteristics by the opening hole 6 can be exhibited.

FIG. 9 shows a state in which the piezoelectric acoustic component A is surface-mounted on a circuit board B and sound is generated from the piezoelectric acoustic component A. In FIG. 9, a region S1 indicates a sound wave region emitted from the sound emitting hole 5, a region S2 indicates a sound wave region emitted from the open hole 6, and a region S3 is an interference region of both sound waves. When the piezoelectric diaphragm 2 is vibrated at a certain frequency, the sound generated from the sound emitting hole 5 and the sound generated from the open hole 6 are in opposite phases, so that both sounds overlap in the same time and cancel each other. There is a problem of attenuating sound. This phenomenon appears remarkably in a lower frequency region, for example, around 1 to 3 kHz than the resonance frequency (for example, 4 kHz) of the front air chamber 3.

The piezoelectric acoustic component vibrates the diaphragm and generates sound using the resonance of the front air chamber (Helmholtz resonance). The resonance frequency of the front air chamber is determined by the area and height of the front air chamber, the area and length of the sound emission hole, etc., but in the case of a piezoelectric acoustic component that generally generates a single operating sound such as a buzzer, In many cases, the resonance frequency of the front air chamber is set in the vicinity of 4 kHz that is most audible to the human ear. However, depending on the product, there is a case where it is desired to generate a sound having a frequency lower than 4 kHz (for example, around 2 to 3 kHz). In this case, the resonance frequency of the front air chamber must be lowered. In order to lower the resonance frequency of the front air chamber, it is necessary to increase the volume of the front air chamber, and there is a problem that the piezoelectric acoustic component becomes large.

9A shows an example of a relatively large piezoelectric acoustic component A. When the product size is reduced as shown in FIG. 9B, the sound emitting holes 5 and the open holes 6 are formed. Since they are close to each other, the area S3 where the sounds cancel each other is widened, and the sound generated from the sound emission hole 5 is greatly attenuated. Thus, the effect of the relationship between the distance between the sound emitting hole and the opening hole and the decrease in sound pressure becomes more pronounced as the distance becomes shorter. Further, when the size of the piezoelectric acoustic component is reduced, the area of the diaphragm is also reduced, and the sound pressure is also reduced. For these reasons, in order to obtain a sound pressure of 80 dB or more, which is generally required as a buzzer, there has been a limit to the miniaturization of piezoelectric acoustic components. In addition, the actual sound pressure performance of the piezoelectric acoustic component is affected by the mounting environment and generally has a problem that it is inferior to the nominal performance. In other words, when the open hole is formed on the side surface near the bottom surface of the piezoelectric acoustic component, when mounted on the circuit board, the open hole opens near the surface of the circuit board. This is because the presence or absence of surface-mounted components obstructs the entry and exit of air from the open hole.
JP 2000-310990 A

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electroacoustic transducer that can further reduce the size of the piezoelectric acoustic component and can effectively generate sound having a frequency lower than the resonance frequency of the front air chamber without attenuation. There is.

In order to achieve the above object, the first embodiment of the present invention accommodates a piezoelectric diaphragm that bends and vibrates when an alternating signal is applied between the electrodes, and the piezoelectric diaphragm. A case partitioned into a front air chamber and a rear air chamber; a sound emitting hole that communicates the front air chamber of the case with the outside; and an open hole that communicates the rear air chamber of the case with the outside. In the electroacoustic transducer formed by surface mounting the piezoelectric acoustic component on the circuit board, the sound emitting hole is formed on the surface of the case that does not face the circuit board, and the open hole is the surface of the case that faces the circuit board. A through hole is formed in a portion of the circuit board corresponding to the open hole, and the surface of the case provided with the open hole is substantially in the circuit board in a state where the piezoelectric acoustic component is surface-mounted on the circuit board. The piezoelectric diaphragm is in close contact with Wavenumber f ₁ is set lower than the resonance frequency f ₀ of the front air chamber, to provide an electroacoustic transducer, characterized in that actuating the piezoelectric vibrating plate at a resonance frequency f ₁ near the frequency.

According to a second embodiment of the present invention, a piezoelectric diaphragm that bends and vibrates when an alternating signal is applied between the electrodes, and the piezoelectric diaphragm are housed. A circuit board comprising a piezoelectric acoustic component comprising: a case partitioned into a plurality of cases; a sound emitting hole that communicates the front air chamber of the case with the outside; and an open hole that communicates the rear air chamber of the case with the outside. In the electroacoustic transducer formed on the surface, the sound emitting hole is formed on the surface of the case facing the circuit board, and the open hole is formed on the surface of the case not facing the circuit board. A through hole is formed in a portion of the circuit board corresponding to the hole, and the surface of the case provided with the sound emitting hole is substantially in close contact with the circuit board in a state where the piezoelectric acoustic component is surface-mounted on the circuit board. , the resonance frequency f ₁ of the piezoelectric diaphragm of the front air chamber It is set lower than the frequency f ₀ sounding, to provide an electroacoustic transducer, characterized in that actuating the piezoelectric vibrating plate at a resonance frequency f ₁ near the frequency.

In the present invention, the sound emitting hole and the opening hole are not opened on the same surface side of the circuit board, but are opened on different surfaces, and the piezoelectric diaphragm is driven at a frequency lower than the resonance frequency of the front air chamber. . In the conventional case, when the piezoelectric diaphragm is driven at a frequency equal to or lower than the resonance frequency of the front air chamber, the sound generated from the sound emitting hole and the sound generated from the open hole are in opposite phases to each other. There is a problem that the sound is attenuated by canceling each other. On the other hand, in the present invention, since the sound emitting hole and the opening hole are opened on different surfaces of the circuit board, the circuit board serves as a sound insulating wall and can prevent an interference phenomenon. As a result, the sound pressure characteristic of the sound emitting hole alone can be obtained. As for the sound pressure characteristic of the sound emitting hole alone, the maximum sound pressure can be obtained near the resonance frequency of the diaphragm. This sound pressure is superior to the total sound pressure when the sound emission hole and the opening hole are opened on the same surface side of the circuit board, and because it is lower than the resonance frequency of the front air chamber, Sound suitable for operation sound can be generated. Furthermore, since a large sound pressure can be generated at a frequency lower than the resonance frequency of the front air chamber, the piezoelectric acoustic component can be further reduced in size. Since the open hole is opened through the through hole of the opposing circuit board, even if another component is surface-mounted in the vicinity of the piezoelectric acoustic component, the performance of the open hole is not affected by the component. Therefore, the performance close to the nominal performance can be obtained as the actual sound pressure performance of the piezoelectric acoustic component.

In the present invention, the resonance frequency f ₁ of the piezoelectric diaphragm is set lower than the resonance frequency of the front air chamber, and the piezoelectric diaphragm is operated at a frequency near the resonance frequency f ₁ . The resonance frequency of the front air chamber is set by the area and height of the front air chamber and the area and length of the sound emission hole as described above. The resonance frequency of the front air chamber is generally set in the vicinity of 4 kHz that can be easily heard by the human ear. However, in order to make the resonance frequency lower than this, it is necessary to increase the volume of the front air chamber, that is, the case. The downsizing of the product is impaired. On the other hand, the resonance frequency f ₁ of the piezoelectric diaphragm is set depending on the size and thickness thereof, but lowering the resonance frequency (for example, around 2 to 3 kHz) can be realized without impairing downsizing. Therefore, if the piezoelectric diaphragm is operated at a frequency in the vicinity of the resonance frequency f ₁ , the operational effects of the present invention can be achieved.

In the present invention, the piezoelectric diaphragm is operated at a frequency in the vicinity of the resonance frequency f _1, but is preferably operated at a frequency f _d defined by the following equation.
0.9f ₁ ≦ f _d ≦ 1.1f ₁
The piezoelectric diaphragm can obtain a large sound pressure in the vicinity of the resonance frequency f ₁ , but if it deviates from this, the sound pressure greatly decreases. If the resonance frequency f ₁ is in the range of 0.9 to 1.1 times, a sound pressure near the maximum sound pressure can be obtained.

In the first embodiment of the present invention, the opening hole is formed in the surface of the case facing the circuit board, the through hole is formed in the portion of the circuit board corresponding to the opening hole, and the piezoelectric acoustic component is surface-mounted on the circuit board. In this state, the surface of the case provided with the sound emission hole is substantially adhered to the circuit board. However, in the second embodiment, the sound emission hole is formed on the surface of the case facing the circuit board, A through hole is formed in a corresponding circuit board portion, and the surface of the case provided with the sound emission hole is substantially adhered to the circuit board in a state where the piezoelectric acoustic component is surface-mounted on the circuit board. Also in this case, as in the first embodiment, the sound emitted from the sound emitting hole and the sound emitted from the open hole are shielded by the circuit board. Sound pressure characteristics of a single hole can be obtained.

According to the first embodiment of the present invention, in the electroacoustic transducer in which the piezoelectric acoustic component is surface-mounted on the circuit board, the sound emitting hole is formed on the surface of the case that does not face the circuit board, and the open hole faces the circuit board. Since the opening hole is made to correspond to the through hole of the circuit board, the interference phenomenon between the sound generated from the sound emitting hole and the sound generated from the opening hole can be reliably prevented. Therefore, the sound pressure characteristic of the sound emitting hole alone can be obtained. When the piezoelectric diaphragm is operated near the resonance frequency of the piezoelectric diaphragm lower than the resonance frequency of the front chamber, the sound pressure characteristics of the sound emitting hole itself are the same as when the sound emitting hole and the open hole are opened on the same plane. An electroacoustic transducer that is superior to the total sound pressure and has excellent sound pressure characteristics at a low frequency can be obtained. In addition, even if the piezoelectric acoustic component is downsized, the sound generated from the sound emitting hole is not attenuated by the sound generated from the open hole, and a large sound pressure can be obtained from the piezoelectric diaphragm. Is possible.

According to the second embodiment of the present invention, the sound emitting hole is formed on the surface of the case facing the circuit board, the through hole is formed in the portion of the circuit board corresponding to the sound emitting hole, and the piezoelectric acoustic component is attached to the circuit board. Since the surface of the case provided with the sound emitting hole is substantially in close contact with the circuit board in the surface mounted state, the sound emitted from the sound emitting hole and the open hole are emitted as in the first embodiment. The circuit board can prevent an interference phenomenon with the sound to be heard, and the sound pressure characteristics of the sound emitting hole alone can be obtained.

Hereinafter, preferred embodiments of the present invention will be described based on examples.

1 and 2 show an electroacoustic transducer according to a first embodiment of the present invention. This electroacoustic transducer is composed of a circuit board 10 and a piezoelectric acoustic component 20 mounted on the surface thereof. The piezoelectric acoustic component 20 is suitable for use in generating a single frequency sound such as a buzzer or a sounder, and its structure is substantially the same as a known piezoelectric acoustic component. That is, it includes a rectangular parallelepiped case 21 and a piezoelectric diaphragm 30 accommodated in the case 21, and the case 21 is constituted by a concave case body 22 and a flat cover 23. The piezoelectric vibration plate 30 may have a structure in which a piezoelectric body is attached to a metal plate, or may be composed only of a piezoelectric body, and flexurally vibrates by applying an alternating voltage (AC voltage or rectangular wave voltage) Any device that generates sound waves may be used. External connection terminals 24 and 25 are provided at the bottoms of the two opposite sides of the case body 22, and a piezoelectric diaphragm 30 is placed on the step provided inside the case body 22, and a sealing material (not shown). It is sealed and fixed by. Each electrode of the piezoelectric diaphragm 30 is connected to the external connection terminals 24 and 25 by a known method. The inside of the case 21 is partitioned into a front air chamber 26 and a rear air chamber 27 by the piezoelectric diaphragm 30, and a sound emitting hole 28 that connects the front air chamber 26 and the outside is formed in the upper edge of the side wall of the case 21. The bottom surface (mounting surface) of the case 21 is formed with an open hole 29 that allows the rear air chamber 27 to communicate with the outside. In this embodiment, the sound emitting hole 28 is formed at the boundary between the case main body 22 and the cover 23, that is, at the side wall of the case 21, but it is needless to say that it may be formed at the cover 23 (the top surface of the case 21). .

The circuit board 10 is provided with pad electrodes 11 and 12 corresponding to the external connection terminals 24 and 25 of the piezoelectric acoustic component 20, and an area between the pad electrodes 11 and 12 corresponds to the open hole 29. A through hole 13 is provided. The through hole 13 has a diameter larger than the diameter of the open hole 29, so that the open hole 29 falls within the range of the through hole 13 even if there is a slight misalignment when the piezoelectric acoustic component 20 is surface-mounted. Designed. The pad electrodes 11, 12 and the external connection terminals 24, 25 are connected by solder 14, and the piezoelectric acoustic component 20 is surface-mounted on the circuit board 10. As a result, the bottom surface of the piezoelectric acoustic component 20 is substantially in close contact with the upper surface of the circuit board 10 to prevent sound emitted from the opening hole 29 from leaking to the upper surface side of the circuit board 10.

As described above, the sound from the sound emission hole 28 is emitted to the upper surface side of the circuit board 10, and the sound from the opening hole 29 is emitted to the lower surface side of the circuit board 10 through the through hole 13. Do not interfere with each other, and individual sound pressure characteristics can be obtained. In particular, when the piezoelectric diaphragm 30 is driven at its resonance frequency (fundamental frequency), as will be described later, the sound pressure characteristic of the sound emitting hole alone is higher than the total characteristic of the sound emitting hole and the open hole. Therefore, there is an advantage that the sound pressure performance is improved. In addition, since the resonance frequency of the piezoelectric diaphragm 30 can be made lower than the resonance frequency of the front air chamber, it can be made lower than the conventional electroacoustic transducer using the resonance frequency of the front air chamber. Further, since the sound pressure performance is not easily affected by the mounting environment, it is possible to obtain performance close to the nominal performance in the mounted state.

When miniaturization of the piezoelectric acoustic component 20 progresses, there may occur a trouble that the circuit board 10 is mounted in the reverse direction. In the above embodiment, the sound emitting hole 28 is formed at the upper end of the side wall of one side of the rectangular parallelepiped case 21, the open hole 29 is near the side wall facing the side wall provided with the sound emitting hole 28, and the center part of the bottom wall It is formed at a position biased to one side. The external connection terminals 24 and 25 are formed at the center position of the side wall orthogonal to the side wall provided with the sound emission hole 28. For this reason, when the circuit board 10 is mounted in the reverse direction, the through hole 13 and the opening hole 29 do not correspond to each other, so that a mounting error can be easily determined. Thus, by giving directionality to the piezoelectric acoustic component 20, the sound emission hole 28 can be opened in a certain direction of the circuit board 10, and a desired sound pressure performance can always be obtained. Further, since the sound emitting hole 28 is formed in the side wall portion of the case 21, in other words, the sound emitting hole 28 is not formed on the top surface of the case 21, when the piezoelectric acoustic component 20 is picked up and mounted, The suction pad can surely suck the top surface of the case 21, and the problem that the suction negative pressure acts on the diaphragm and breaks the diaphragm can be prevented.

Here, in order to confirm the effect of the present invention, the sound pressure characteristics were measured using a piezoelectric acoustic component 20 'as shown in FIG. The piezoelectric acoustic component 20 ′ is different from the piezoelectric acoustic component 20 shown in FIGS. 1 and 2 only in the position and shape of the opening hole 29 ′, and the other structure is the same. The opening hole 29 ′ is a rectangular hole that opens in two directions, that is, the bottom surface side and the side surface side, along the bottom side of the side wall that faces the side wall provided with the sound emission hole 28.

FIG. 4 shows some examples in which the piezoelectric acoustic component 20 ′ is surface-mounted on the circuit board 10 and its sound pressure characteristics are measured using the microphone 40. Here, the size of the piezoelectric acoustic component 20 ′ is 12 mm × 12 mm × 3 mm, the size of the circuit board 10 is 100 mm × 100 mm, and the piezoelectric acoustic component 20 ′ is surface-mounted on the central portion of the circuit board 10. The microphone 40 was disposed at a position 100 mm away from the circuit board 10.

4A shows the sound (total characteristics) from both the sound emitting hole 28 and the open hole 29 ′ measured by the microphone 40 disposed on the surface side of the circuit board 10. There are no through holes. 4B, the through-hole 13 is provided at the position of the circuit board 10 facing the open hole 29 ′, and only the sound from the sound emission hole 28 (sound emission characteristic) is arranged on the surface side of the circuit board 10. FIG. Measured with the microphone 40. The side surface of the opening hole 29 ′ is sealed with a sealing material 41, and sound from the opening hole 29 ′ is emitted only to the back surface side of the circuit board 10. 4C, in contrast to FIG. 4B, the microphone 40 is disposed on the back side of the circuit board 10, and only the sound (open hole characteristics) from the open hole 29 ′ is measured by the microphone 40. It is a thing.

FIG. 5 is a frequency-sound pressure characteristic diagram showing the measurement results in FIGS. The thick solid line in FIG. 5 indicates overall characteristics, the thin line in FIG. 5 indicates sound emission hole characteristics, and the alternate long and short dash line in FIG. 5 indicates open hole characteristics. As apparent from FIG. 5, at the resonance frequency f ₀ (about 4.4 kHz) of the front air chamber, both of the three sound pressure characteristics can obtain a relatively high sound pressure level (about 79 dB). The generally required 80 dB is not reached. On the other hand, on the lower frequency side than the resonance frequency f ₀ of the front air chamber, the open hole characteristic is greatly reduced and the overall characteristic is also deteriorated due to the interference phenomenon, whereas the sound emission hole characteristic is higher than the overall characteristic. The pressure level is maintained. Particularly in the vicinity of the resonance frequency f ₁ (about 2.7 kHz) of the diaphragm, the sound emission hole characteristic has a maximum sound pressure level (about 83 dB) higher than the sound pressure level at the resonance frequency f ₀ of the front air chamber. . If the frequency f _{d of the} applied voltage is in the range of 0.9 f ₁ ≦ f _d ≦ 1.1 f ₁ (where f ₁ is the resonance frequency of the diaphragm), the sound emitting hole characteristic is a large sound pressure of 80 dB or more. Is obtained, which is a desirable sound pressure level as a buzzer. Thus, it was demonstrated that when the sound emitting hole characteristics are used and the diaphragm is driven in the vicinity of the resonance frequency f ₁ , a high sound pressure can be obtained at a frequency lower than the resonance frequency f ₀ of the front air chamber.

FIG. 6 shows a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. In this embodiment, the piezoelectric acoustic component 20 is surface-mounted with the surface of the case 21 provided with the sound emission holes 28 facing the circuit board 10. Specifically, the sound emitting hole 28 is formed on the surface of the case 21 facing the circuit board 10, and the open hole 29 is formed on the surface of the case 21 not facing the circuit board 10. In the state where the through hole 13 is formed in the portion of the circuit board 10 corresponding to the sound emission hole 28 and the piezoelectric acoustic component 20 is surface-mounted on the circuit board 10, the surface of the case 21 provided with the sound emission hole 28 is the surface of the circuit board 10. Is substantially in close contact. The through hole 13 is preferably a hole having a larger opening area than the sound emitting hole 28.

In this embodiment, similarly to the first embodiment, the resonance frequency f ₁ of the piezoelectric diaphragm is set lower than the resonance frequency f ₀ of the front air chamber, and the piezoelectric diaphragm is set at a frequency near the resonance frequency f _1. Operate. Since the sound emitting hole 28 and the opening hole 29 are opened on different surfaces of the circuit board 10, the circuit board 10 serves as a sound insulating wall, and the interference phenomenon of sound from both the holes 28 and 29 can be prevented.

The present invention is not limited to the above embodiments. In the above embodiment, the case of the piezoelectric acoustic component has a rectangular parallelepiped shape, but may have a cylindrical shape. In the first embodiment, the sound emitting hole is opened on the side wall of the case. However, it may be a surface of the case that does not face the circuit board, and may be provided on the top surface (cover), for example. In the second embodiment, the opening hole is provided in the corner portion of the case. However, it may be formed on any surface as long as the surface of the case does not face the circuit board.

It is the perspective view and bottom view of 1st Example of the piezoelectric acoustic component which concerns on this invention. It is sectional drawing of the state which surface-mounted the piezoelectric acoustic component shown in FIG. 1 on the circuit board. It is the perspective view and bottom view of the piezoelectric acoustic component used for experiment. Several examples are shown in which the piezoelectric acoustic component shown in FIG. 3 is surface-mounted on a circuit board and the sound from the piezoelectric acoustic component is measured. FIG. 5 is a sound pressure characteristic diagram measured by the method shown in FIG. 4. It is sectional drawing of 2nd Example of the electroacoustic transducer which concerns on this invention. It is a perspective view of the conventional piezoelectric acoustic component. It is sectional drawing of the piezoelectric acoustic component shown in FIG. FIG. 8 is a propagation diagram of sound waves when the piezoelectric acoustic component shown in FIG. 7 is mounted on a circuit board and caused to ring.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Circuit board 11, 12 Electrode pad 13 Through-hole 20 Piezoelectric acoustic component 21 Case 24, 25 External connection terminal 26 Front air chamber 27 Rear air chamber 28 Sound emission hole 29 Open hole

Claims (2)

A piezoelectric vibration plate that bends and vibrates by applying an alternating signal between the electrodes; a case in which the piezoelectric vibration plate is housed; and an internal space is partitioned into a front air chamber and a rear air chamber by the piezoelectric vibration plate; An electroacoustic conversion formed by surface-mounting a piezoelectric acoustic component having a sound emitting hole communicating the front air chamber of the case with the outside and an open hole communicating the rear air chamber of the case with the outside on the circuit board. In the vessel
The sound emitting hole is formed on the surface of the case that does not face the circuit board,
The open hole is formed on the surface of the case facing the circuit board,
A through hole is formed in a portion of the circuit board corresponding to the open hole,
In a state where the piezoelectric acoustic component is surface-mounted on a circuit board, the surface of the case provided with the open hole is substantially in close contact with the circuit board,
The resonance frequency f ₁ of the piezoelectric vibrating plate is set lower than the resonance frequency f ₀ of the front air chamber, the electro-acoustic transducer, characterized in that actuating the piezoelectric vibrating plate at a resonance frequency f ₁ near the frequency. A piezoelectric vibration plate that bends and vibrates by applying an alternating signal between the electrodes; a case in which the piezoelectric vibration plate is housed; and an internal space is partitioned into a front air chamber and a rear air chamber by the piezoelectric vibration plate; An electroacoustic conversion formed by surface-mounting a piezoelectric acoustic component having a sound emitting hole communicating the front air chamber of the case with the outside and an open hole communicating the rear air chamber of the case with the outside on the circuit board. In the vessel
The sound emitting hole is formed on the surface of the case facing the circuit board,
The open hole is formed on the surface of the case that does not face the circuit board,
A through hole is formed in a portion of the circuit board corresponding to the sound emitting hole,
In a state where the piezoelectric acoustic component is surface-mounted on a circuit board, the surface of the case provided with the sound emitting hole is substantially in close contact with the circuit board,
The resonance frequency f ₁ of the piezoelectric vibrating plate is set lower than the resonance frequency f ₀ of the front air chamber, the electro-acoustic transducer, characterized in that actuating the piezoelectric vibrating plate at a resonance frequency f ₁ near the frequency.

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