Ultrasonic transducer and parametric speaker including same

Abstract

The present invention comprises a first vibration plate (110), at least one frame body (120), and at least one ultrasonic vibrator (130). The at least one frame body (120) extends in a longitudinal direction and is joined to the first vibration plate (110). The at least one ultrasonic vibrator (130) is attached to the at least one frame body (120), and faces the first vibration plate (110) with an interval therebetween. The first vibration plate (110) resonantly vibrates in antiphase with the at least one ultrasonic vibrator (130) in a direction orthogonal to the first vibration plate (110). The dimension in the longitudinal direction inside the at least one frame body (120) is at least 4 times the dimension in the short direction orthogonal to the longitudinal direction inside the at least one frame body (120).

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic transducer and a parameter measuring device including the same. to Regarding Rickspeakers. [Background technology]

[0002] Prior documents disclosing the configuration of an ultradirectional acoustic device include Japanese Patent Laid-Open Publication No. 2003-47085 (Patent Document 1) and Japanese Patent No. 6333480 (Patent Document 2). The ultradirectional acoustic device described in Patent Document 1 is configured by deploying multiple ultrasonic transducers on a single printed circuit board and arranging them so that the outer periphery is approximately circular. The multiple ultrasonic transducers are divided into two groups installed at different heights.

[0003] The ultradirectional acoustic device described in Patent Document 2 includes a first ultrasonic emitter and a second ultrasonic emitter. The second ultrasonic emitter is disposed on the axis of the first ultrasonic emitter and in front of the radiation surface. The phase of the carrier signal emitted by the second ultrasonic emitter is opposite to the phase of the carrier signal included in the signal emitted by the first ultrasonic emitter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-47085 [Patent Document 2] Patent No. 6333480 Summary of the Invention [Problem to be solved by the invention]

[0005] In the superdirectional acoustic device described in Patent Document 1, a plurality of ultrasonic transducers are arranged in two groups at different installation heights, resulting in a complex configuration. In the superdirectional acoustic device described in Patent Document 2, a second ultrasonic emitter is arranged outside a first ultrasonic emitter, resulting in an increased size of the device.

[0006] The present invention has been made in view of the above-mentioned problems, and provides an ultrasonic transducer and a parameter measuring device including the same that can increase the sound pressure level with a simple and compact configuration. to The object of the present invention is to provide a comfortable speaker. [Means for solving the problem]

[0007] An ultrasonic transducer according to the present invention comprises a first diaphragm, at least one frame body, and at least one ultrasonic vibrator. The at least one frame body extends in a longitudinal direction and is joined to the first diaphragm. The at least one ultrasonic vibrator is attached to the at least one frame body and faces the first diaphragm at an interval. The first diaphragm resonates and vibrates in an opposite phase to the at least one ultrasonic vibrator in a direction perpendicular to the first diaphragm. The longitudinal dimension inside the at least one frame body is four or more times the lateral dimension inside the at least one frame body that is perpendicular to the longitudinal direction. [Effects of the Invention]

[0008] According to the present invention, it is possible to increase the sound pressure level in an ultrasonic transducer with a simple and compact configuration. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a longitudinal sectional view showing the configuration of an ultrasonic transducer according to a first embodiment of the present invention. [Figure 2] 1 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a first embodiment of the present invention. [Figure 3] 1 is a perspective view showing the configuration of a frame body included in an ultrasonic transducer according to a first embodiment of the present invention. [Figure 4] 1 is a cross-sectional view showing the configuration of an ultrasonic vibrator included in an ultrasonic transducer according to a first embodiment of the present invention. [Figure 5]1 is a perspective view showing a displacement state obtained by simulation analysis using a finite element method when the ultrasonic transducer according to the first embodiment of the present invention transmits or receives ultrasonic waves. FIG. [Figure 6] 6 is a cross-sectional view of the ultrasonic transducer of FIG. 5 as viewed from the direction of the arrows along line VI-VI. [Figure 7] 10 is a graph showing a simulation analysis using a finite element method of the change in the resonance frequency of the first diaphragm when the longitudinal dimension is changed while the lateral dimension inside the frame is fixed. [Figure 8] 10 is a graph showing a simulation analysis using a finite element method of the change in the sound pressure of ultrasonic waves transmitted from an ultrasonic transducer when the longitudinal dimension is changed while the lateral dimension inside the frame body is fixed. [Figure 9] FIG. 2 is a perspective view showing the configuration of an ultrasonic element array according to a first comparative example. [Figure 10] 10 is a graph showing the results of a simulation analysis using a finite element method on the relationship between the sound pressure of ultrasonic waves transmitted from the ultrasonic transducer and the thickness of the first diaphragm. [Figure 11] 10 is a graph showing the results of a simulation analysis using the finite element method of the relationship between the internal stress (value normalized per sound pressure) generated in the ultrasonic transducer in the third direction (Z-axis direction) and the thickness of the first diaphragm. [Figure 12] 10 is a graph showing the results of a simulation analysis using the finite element method of the relationship between the displacement of the first diaphragm and the frequency of the ultrasonic vibrator in the ultrasonic transducer according to this embodiment, the ultrasonic transducer according to the first modified example, and the ultrasonic transducer according to the second modified example. [Figure 13] FIG. 10 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a third modified example. [Figure 14] FIG. 10 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a fourth modified example. [Figure 15] FIG. 11 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a fifth modified example. [Figure 16] FIG. 10 is a longitudinal sectional view showing the configuration of an ultrasonic transducer according to a sixth modified example of the first embodiment of the present invention. [Figure 17] FIG. 10 is a side view showing the configuration of an ultrasonic transducer according to a second embodiment of the present invention. [Figure 18] FIG. 18 is a rear view of the ultrasonic transducer shown in FIG. 17 as seen from the direction of arrow XVIII. [Figure 19] FIG. 10 is an exploded perspective view showing a stacked state in a step of stacking and bonding components of an ultrasonic transducer according to a second embodiment of the present invention. [Figure 20] 10 is a plan view showing the positional relationship in a first direction (X-axis direction) in a step of cutting a piezoelectric body of an ultrasonic transducer according to a second embodiment of the present invention. FIG. [Figure 21] FIG. 10 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when an ultrasonic transducer according to a second embodiment of the present invention transmits or receives ultrasonic waves. [Figure 22] FIG. 10 is a perspective view showing the configuration of an ultrasonic element array according to a second comparative example. [Figure 23] 10 is a graph showing actual measurements of the transition of attenuation of sound pressure level over propagation distance in the ultrasonic transducer according to this embodiment and the ultrasonic transducer according to the second comparative example. [Figure 24] FIG. 10 is a side view showing a state in which an ultrasonic transducer according to a modification of this embodiment that configures a phased array system transmits ultrasonic waves in a plane in a third direction (Z-axis direction). [Figure 25] 10 is a diagram showing a drive start delay time in a first state in which the ultrasonic transducers A to G are caused to emit ultrasonic waves at the same timing by a processing circuit. FIG. [Figure 26] FIG. 10 is a side view showing a state in which an ultrasonic transducer according to a modified example of the present embodiment transmits ultrasonic waves in a plane in an oblique direction inclined toward the first direction (X-axis direction) with respect to the third direction (Z-axis direction). [Figure 27] 10 is a diagram showing a drive start delay time in a second state in which ultrasonic transducers G to A are caused to emit ultrasonic waves in this order by the processing circuit. FIG. [Figure 28]FIG. 10 is a side view showing a state in which an ultrasonic transducer according to a modified example of the present embodiment emits ultrasonic waves in a third direction (Z-axis direction) so as to concentrate at the center in the first direction (X-axis direction). [Figure 29] 10 is a diagram showing the drive start delay time in a third state in which ultrasonic waves are transmitted by the processing circuit in the order of ultrasonic transducers A to D and ultrasonic transducers G to D. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, ultrasonic transducers according to embodiments of the present invention will be described with reference to the drawings. In the following description of the embodiments, the same or corresponding parts in the drawings will be denoted by the same reference numerals, and their description will not be repeated. The present invention is applicable to applications requiring high sound pressure ultrasonic waves, such as ultrasonic transducers for parametric speakers, ultrasonic sensors, or non-contact haptics. In the following embodiments, an ultrasonic transducer for a parametric speaker will be described as an example, but the use of the ultrasonic transducer is not limited to this.

[0011] (Embodiment 1) Fig. 1 is a longitudinal sectional view showing the configuration of an ultrasonic transducer according to embodiment 1 of the present invention. Fig. 2 is an exploded perspective view showing the configuration of the ultrasonic transducer according to embodiment 1 of the present invention. As shown in Figs. 1 and 2, an ultrasonic transducer 100 according to embodiment 1 of the present invention includes a first diaphragm 110, a frame 120, and an ultrasonic vibrator 130.

[0012] The first diaphragm 110 has a flat plate shape. The first diaphragm 110 is made of an aluminum alloy such as aluminum-containing duralumin, or a metal such as stainless steel. In this embodiment, the first diaphragm 110 is made of stainless steel. The thickness of the first diaphragm 110 is, for example, not less than 0.1 mm and not more than 0.2 mm.

[0013] The frame body 120 has a rectangular annular shape. The frame body 120 has a short side direction along a first direction (X-axis direction) and a long side direction along a second direction (Y-axis direction). The frame body 120 extends in the second direction (Y-axis direction). The axial direction of the frame body 120 is along a third direction (Z-axis direction). One end of the frame body 120 in the third direction (Z-axis direction) is bonded to the first diaphragm 110 with a bonding agent made of epoxy resin or the like.

[0014] The frame 120 is formed from a metal such as an aluminum alloy or stainless steel, glass epoxy, or resin. From the viewpoint of suppressing changes in the characteristics of the ultrasonic transducer 100 due to temperature changes, the frame 120 is preferably made of metal. On the other hand, from the viewpoint of lowering the frequency of the ultrasonic waves transmitted or received by the ultrasonic transducer 100 and from the viewpoint of miniaturizing the ultrasonic transducer 100, the frame 120 is preferably made of resin. In this embodiment, the frame 120 is made of stainless steel. The thickness of the frame 120 is, for example, 0.2 mm or more and 0.8 mm or less.

[0015] Fig. 3 is a perspective view showing the configuration of a frame body included in the ultrasonic transducer according to the first embodiment of the present invention. As shown in Fig. 3, the frame body 120 has a pair of long sides 121 extending in the second direction (Y-axis direction) and a pair of short sides 122 extending in the first direction (X-axis direction). The average distance between the short sides 122 is four or more times the shortest distance between the long sides 121. In other words, the longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame body 120 is four or more times the lateral dimension L2 in the first direction (X-axis direction) inside the frame body 120.

[0016] The corners between the long side portion 121 and the short side portion 122 may be chamfered. The short side portion 122 is not limited to being linear when viewed from the third direction (Z-axis direction), and may be an arc-shaped portion that is convex toward the inside of the frame body 120 or an arc-shaped portion that is convex toward the outside of the frame body 120.

[0017] The resonance frequency of first diaphragm 110 can be adjusted by changing short-side dimension L2 in the first direction (X-axis direction) inside frame body 120. For example, when the resonance frequency of first diaphragm 110 is set to 100 kHz or higher, short-side dimension L2 is 1.5 mm or more and 3 mm or less.

[0018] The longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame body 120 is four or more times the short dimension L2, and from the viewpoint of increasing the sound pressure level of the ultrasonic waves transmitted by the ultrasonic transducer 100, the longitudinal dimension L1 is, for example, 20 mm or more.

[0019] Fig. 4 is a cross-sectional view showing the configuration of an ultrasonic vibrator included in the ultrasonic transducer according to embodiment 1 of the present invention. As shown in Fig. 1, ultrasonic vibrator 130 is attached to frame body 120 and faces first diaphragm 110 with a gap therebetween. Specifically, ultrasonic vibrator 130 is attached to the other end of frame body 120 in the third direction (Z-axis direction), and faces first diaphragm 110 with the inner space of frame body 120 sandwiched therebetween.

[0020] As shown in FIGS. 1, 2, and 4, the ultrasonic vibrator 130 is a piezoelectric element including a piezoelectric body 131. As shown in FIG. 4, in this embodiment, the ultrasonic vibrator 130 includes two stacked piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 are different from each other. Specifically, the polarization directions Dp of the two piezoelectric bodies 131 face each other in the third direction (Z-axis direction). The two piezoelectric bodies 131 are sandwiched between a first electrode 132 and a second electrode 133, and an intermediate electrode 134 is disposed between the two piezoelectric bodies 131. The first electrode 132 and the second electrode 133 are electrically connected to a processing circuit 140 to which an AC voltage can be applied. The ultrasonic vibrator 130 is a so-called series-type bimorph piezoelectric vibrator. The total thickness of the two piezoelectric bodies 131 is, for example, 0.5 mm or more and 0.85 mm or less.

[0021] Fig. 5 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to the first embodiment of the present invention transmits or receives ultrasonic waves. Fig. 6 is a cross-sectional view of the ultrasonic transducer of Fig. 5 as seen from the direction of the arrows along line VI-VI. The simulation analysis conditions were as follows: the thickness of first diaphragm 110 was 0.1 mm, the combined thickness of two piezoelectric bodies 131 was 0.8 mm, the longitudinal dimension L1 inside frame body 120 was 20 mm, the lateral dimension L2 was 2 mm, and the thickness of frame body 120 in the third direction (Z-axis direction) was 0.4 mm.

[0022] 5 and 6, in the vibration mode of the ultrasonic transducer 100 according to the first embodiment of the present invention, the first diaphragm 110 resonates in an opposite phase to the ultrasonic vibrator 130 in a third direction (Z-axis direction) perpendicular to the first diaphragm 110. That is, as shown in Fig. 6, the displacement direction of the resonant vibration Bm of the first diaphragm 110 and the displacement direction of the resonant vibration Bp of the ultrasonic vibrator 130 are opposite to each other in the third direction (Z-axis direction). In this embodiment, the resonant frequencies of the first diaphragm 110 and the ultrasonic vibrator 130 are 100 kHz or higher.

[0023] In first diaphragm 110, middle portion 110c located at the middle in the longitudinal direction inside frame body 120 becomes the antinode of the resonant vibration, and end portions 110e located at both ends in the longitudinal direction inside frame body 120 become nodes of the resonant vibration. In other words, the portion of first diaphragm 110 located above the inner space of frame body 120 becomes the vibration region that resonates. The longitudinal dimension of the vibration region of first diaphragm 110 is the same as longitudinal dimension L1 inside frame body 120, and the lateral dimension of the vibration region of first diaphragm 110 is the same as lateral dimension L2 inside frame body 120.

[0024] Here, the relationship between the resonance frequency of first diaphragm 110 and longitudinal dimension L1 inside frame body 120 will be described.

[0025] Fig. 7 is a graph showing the results of a simulation analysis using the finite element method of the transition of the resonant frequency of the first diaphragm when the longitudinal dimension is changed while the lateral dimension inside the frame is fixed. In Fig. 7, the vertical axis represents the resonant frequency (kHz) of first diaphragm 110, and the horizontal axis represents the longitudinal dimension L1 (mm) inside frame 120. As a condition for the simulation analysis, the lateral dimension L2 inside frame 120 was fixed at 2 mm.

[0026] 7, when the longitudinal dimension L1 inside the frame body 120 is 2 mm, the resonant frequency of the first diaphragm 110 is 220 kHz, and when the longitudinal dimension L1 increases to 8 mm and the longitudinal dimension of the vibration region of the first diaphragm 110 increases, the resonant frequency of the first diaphragm 110 decreases to 122 kHz. Thereafter, even when the longitudinal dimension L1 inside the frame body 120 exceeds 8 mm and the longitudinal dimension of the vibration region of the first diaphragm 110 further increases, the resonant frequency of the first diaphragm 110 remains approximately constant at 122 kHz.

[0027] In other words, the resonant frequency of the first diaphragm 110 is determined by the speed of sound in the first diaphragm 110 and the reflection of vibrations with the frame body 120 as the fixed end, but once the longitudinal dimension L1 inside the frame body 120 exceeds four times the lateral dimension L2, the influence of the lateral dimension L2 becomes dominant in terms of vibration reflection, and the state of vibration reflection does not change even if the longitudinal dimension L1 becomes even larger than four times the lateral dimension L2.

[0028] Next, the results of a simulation analysis using the finite element method on the relationship between the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 100 and the longitudinal dimension L1 inside the frame body 120 will be described.

[0029] Fig. 8 is a graph showing the results of a simulation analysis using the finite element method of the transition of the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer when the longitudinal dimension is changed while the lateral dimension inside the frame body is fixed. In Fig. 8, the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer 100, and the horizontal axis represents the longitudinal dimension L1 (mm) inside the frame body 120. As a simulation analysis condition, the lateral dimension L2 inside the frame body 120 was fixed at 2 mm, and the sound pressure (Pa) was calculated at a position 30 cm away in the third direction (Z-axis direction) from the first diaphragm 110 on the front side of the ultrasonic transducer 100.

[0030] 8, as the longitudinal dimension L1 inside the frame body 120 increases, the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 100 increases. This means that even when the longitudinal dimension of the vibration region of the first diaphragm 110 is increased, the entire vibration region of the first diaphragm 110 between both end portions 110e vibrates. In other words, the area of the vibration region can be increased by the amount that the vibration region of the first diaphragm 110 is longer, and as a result, the change in air pressure due to the vibration of the first diaphragm 110 can be increased, thereby obtaining a high sound pressure.

[0031] In this way, the ultrasonic transducer 100 according to this embodiment can increase the sound pressure while maintaining a substantially constant resonant frequency by increasing the longitudinal dimension of the vibration region of the first diaphragm 110. Furthermore, since there are nodal points at both ends in the longitudinal direction, the ends can be supported or fixed, making it easy to mount the ultrasonic transducer 100.

[0032] Here, an ultrasonic element array according to a first comparative example will be described, which obtains high sound pressure by arranging high-frequency ultrasonic elements side by side.

[0033] 9 is a perspective view showing the configuration of an ultrasonic element array according to a first comparative example. As shown in FIG. 9, in the ultrasonic element array according to the first comparative example, a plurality of ultrasonic elements 800 are arranged side by side at intervals from one another in the second direction (Y-axis direction). In such an ultrasonic element array, there are spaces between the ultrasonic elements 800 where no sound pressure is generated, resulting in low efficiency. Furthermore, because ultrasonic elements 800 with high frequencies of, for example, 100 kHz or more are small in size, it takes time and effort to configure an ultrasonic element array by arranging and mounting a plurality of ultrasonic elements 800.

[0034] The thickness of the first diaphragm 110 included in the ultrasonic transducer 100 according to an embodiment of the present invention will be described in detail below.

[0035] The first diaphragm 110 and the ultrasonic vibrator 130 resonate with each other in opposite phases, resulting in a vibration mode similar to that of a tuning fork. From the viewpoint of maintaining a physical balance between the first diaphragm 110 and the ultrasonic vibrator 130, it is preferable to satisfy the relationship 0.7CpTp / Cv≦Tv≦1.3CpTp / Cv, where Cv is the sound velocity of the shear wave of the first diaphragm 110, Cp is the sound velocity of the shear wave of the piezoelectric body 131, Tv is the thickness of the first diaphragm 110, and Tp is the thickness of the piezoelectric body 131. The sound velocity Cv of the shear wave of the first diaphragm 110 is determined by the material constituting the first diaphragm 110. The sound velocity Cp of the shear wave of the piezoelectric body 131 is determined by the material constituting the piezoelectric body 131. When multiple piezoelectric bodies 131 are stacked in the ultrasonic vibrator 130, the thickness dimension Tp of the piezoelectric body 131 is the sum of the thicknesses of the multiple piezoelectric bodies 131.

[0036] By satisfying the relationship 0.7CpTp / Cv≦Tv≦1.3CpTp / Cv, the physical balance between the first diaphragm 110 and the ultrasonic vibrator 130 during vibration is maintained, and the amplitude of the resonant vibration of the first diaphragm 110 is increased, thereby increasing the sound pressure and suppressing vibration leakage. It is more preferable to satisfy the relationship Tv=CpTp / Cv. From the viewpoint of maintaining the physical balance, when Tp=0.8, it is ideal for the thickness dimension Tv of the first diaphragm 110 to be 0.4, based on the relationship Tv=0.8Cp / Cv.

[0037] Fig. 10 is a graph showing the relationship between the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer and the thickness of the first diaphragm, which was analyzed by simulation using the finite element method. In Fig. 10, the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer 100, and the horizontal axis represents the thickness (mm) of the first diaphragm. As a condition for the simulation analysis, the total thickness Tp of the two piezoelectric bodies 131 was set to 0.8 mm. As shown in Fig. 10, when the thickness of the first diaphragm 110 was 0.4 mm, the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer was at its maximum.

[0038] Fig. 11 is a graph showing the result of a simulation analysis using the finite element method on the relationship between the internal stress (value normalized per sound pressure) generated in the ultrasonic transducer in the third direction (Z-axis direction) and the thickness of the first diaphragm. In Fig. 11, the vertical axis represents the internal stress in the third direction (Z-axis direction) per sound pressure, and the horizontal axis represents the thickness (mm) of the first diaphragm.

[0039] As shown in FIG. 11 , the thinner the first diaphragm 110, the smaller the internal stress (value normalized per sound pressure) in the third direction (Z-axis direction) generated in the ultrasonic transducer 100. In particular, when the thickness of the first diaphragm 110 is 0.24 mm or less, the internal stress (value normalized per sound pressure) in the third direction (Z-axis direction) generated in the ultrasonic transducer 100 is significantly smaller. By reducing the internal stress (value normalized per sound pressure) in the third direction (Z-axis direction) generated in the ultrasonic transducer 100, it is possible to prevent cracks from occurring due to internal stress at the joint between the first diaphragm 110 and the frame 120 and at the joint between the frame 120 and the ultrasonic vibrator 130. On the other hand, if the thickness of the first diaphragm 110 is thinner than 0.1 mm, the first diaphragm 110 becomes too soft and is no longer suitable as a vibrator that emits ultrasonic waves.

[0040] That is, from the viewpoint of generating ultrasonic waves with high sound pressure while suppressing the occurrence of cracks due to internal stress, it is preferable to satisfy the relationship 0.25CpTp / Cv≦Tv≦0.6CpTp / Cv. In this embodiment, by setting the thickness of the first diaphragm 110 to be 0.1 mm or more and 0.2 mm or less, it is possible to drive the ultrasonic transducer 100 in a state where the internal stress (a value normalized per sound pressure) generated in the ultrasonic transducer 100 in the third direction (Z-axis direction) is low.

[0041] Here, we will explain the results of a simulation analysis using the finite element method on the drive efficiency of an ultrasonic transducer when the ultrasonic vibrator is a bimorph piezoelectric vibrator and when it is a unimorph piezoelectric vibrator. As simulation analysis conditions, in order to match the conditions with the bimorph ultrasonic vibrator 130 shown in Figure 1, the unimorph ultrasonic vibrator also has a structure in which two piezoelectric bodies 131 are bonded together as shown in Figure 1, and a drive voltage is applied to only one of the two piezoelectric bodies 131, while the other piezoelectric body 131 serves as a second diaphragm to which no drive voltage is applied.

[0042] Specifically, in the ultrasonic transducer of the first modified example, a drive voltage is applied to the piezoelectric body 131 adjacent to the frame body 120, and the piezoelectric body 131 not adjacent to the frame body 120 serves as a second vibration plate to which no drive voltage is applied. In the first modified example, the second vibration plate is provided on the opposite side of the piezoelectric body 131 to which the drive voltage is applied, from the frame body side.

[0043] In the ultrasonic transducer of the second modified example, a drive voltage is applied to the piezoelectric body 131 that is not adjacent to the frame body 120, and the piezoelectric body 131 that is adjacent to the frame body 120 serves as a second vibration plate to which no drive voltage is applied. In the second modified example, the second vibration plate is provided on the frame body side of the piezoelectric body 131 to which the drive voltage is applied.

[0044] Fig. 12 is a graph showing the results of a simulation analysis using the finite element method on the relationship between the displacement of the first diaphragm and the frequency of the ultrasonic vibrator in the ultrasonic transducer according to this embodiment, the ultrasonic transducer according to the first modification, and the ultrasonic transducer according to the second modification. In Fig. 12, the vertical axis represents the displacement of the first diaphragm 110, and the horizontal axis represents the frequency (kHz) of the ultrasonic vibrator 130. The data for the ultrasonic transducer 100 according to this embodiment is shown by a solid line, the data for the ultrasonic transducer according to the first modification is shown by a dotted line, and the data for the ultrasonic transducer according to the second modification is shown by a dashed-dotted line.

[0045] 12, when the displacement of the first diaphragm 110 in the ultrasonic transducer 100 according to this embodiment is taken as 100%, the displacement of the first diaphragm 110 in the ultrasonic transducer according to the first modified example is 77.2%, and the displacement of the first diaphragm 110 in the ultrasonic transducer according to the second modified example is 36.9%. When the free capacitance of the piezoelectric element in the ultrasonic transducer 100 according to this embodiment is taken as 100%, the free capacitance of the piezoelectric element in the ultrasonic transducer according to the first modified example is 54.2%, and the free capacitance of the piezoelectric element in the ultrasonic transducer according to the second modified example is 59.2%.

[0046] When piezoelectric elements are driven with the same voltage, the smaller the free capacitance of the piezoelectric element, the smaller the power consumption. The ultrasonic transducer according to the first modification example can displace the first diaphragm 110 by nearly 80% of the power consumption of the ultrasonic transducer 100 according to this embodiment, and is therefore found to be highly efficient.

[0047] In this embodiment, the ultrasonic vibrator 130 is a so-called series-type bimorph piezoelectric vibrator, but the ultrasonic vibrator 130 may be another type of piezoelectric vibrator. An ultrasonic vibrator of an ultrasonic transducer according to a modification of the first embodiment of the present invention will be described below.

[0048] Fig. 13 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a third modification. As shown in Fig. 13, ultrasonic vibrator 130a according to the third modification is a piezoelectric element including two stacked piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 are the same. Ultrasonic vibrator 130a is a so-called parallel bimorph piezoelectric vibrator.

[0049] Fig. 14 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a fourth modification. As shown in Fig. 14, ultrasonic vibrator 130b according to the fourth modification is a piezoelectric element including four stacked piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 located on the outer sides of the four piezoelectric bodies 131 face one side of the first direction (Z-axis direction), and the polarization directions Dp of the two piezoelectric bodies 131 located on the inner sides of the four piezoelectric bodies 131 face the other side of the first direction (Z-axis direction). Ultrasonic vibrator 130b is a so-called multimorph piezoelectric vibrator.

[0050] Fig. 15 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a fifth modified example. As shown in Fig. 15, ultrasonic vibrator 130c according to the fifth modified example is a piezoelectric element including one piezoelectric body 131. Specifically, piezoelectric body 131 is sandwiched between a first electrode 132 and a second vibration plate 135 made of metal. Ultrasonic vibrator 130c is a so-called unimorph piezoelectric vibrator.

[0051] Fig. 16 is a longitudinal cross-sectional view showing the configuration of an ultrasonic transducer according to a sixth modified example of the first embodiment of the present invention. As shown in Fig. 16, the ultrasonic transducer 100a according to the sixth modified example of the first embodiment of the present invention includes a first diaphragm 110, a frame body 120a, and an ultrasonic vibrator 130. The frame body 120a has a cylindrical shape with a bottom. The frame body 120a is made of metal. A piezoelectric body 131 is attached to the outer bottom surface of the frame body 120a, thereby forming an ultrasonic vibrator that is a unimorph piezoelectric vibrator.

[0052] The ultrasonic transducer 100 according to the first embodiment of the present invention includes a first diaphragm 110, at least one frame body 120, and at least one ultrasonic vibrator 130. The at least one frame body 120 extends in the longitudinal direction and is joined to the first diaphragm 110. The at least one ultrasonic vibrator 130 is attached to the at least one frame body 120 and faces the first diaphragm 110 at an interval. The first diaphragm 110 resonates in an opposite phase to the at least one ultrasonic vibrator 130 in a direction perpendicular to the first diaphragm 110. The longitudinal dimension L1 inside the at least one frame body 120 is four or more times the lateral dimension L2 inside the at least one frame body 120 perpendicular to the longitudinal direction. This allows the ultrasonic transducer 100 to achieve a high sound pressure level with a simple and compact configuration.

[0053] In a parametric speaker including the ultrasonic transducer 100 according to the first embodiment of the present invention, it is possible to reproduce audible sound by modulating the ultrasonic waves emitted from the ultrasonic transducer 100 through modulation driving of the ultrasonic transducer 100. Modulation methods include AM modulation (amplitude modulation) and FM modulation (frequency modulation).

[0054] In the ultrasonic transducer 100 according to the first embodiment of the present invention, the resonant frequency of the first diaphragm 110 and the ultrasonic vibrator 130 is 100 kHz or higher. As will be described later, when the resonant frequency is 100 kHz or higher, the attenuation of sound waves over the propagation distance is large. Therefore, by setting the resonant frequency of the first diaphragm 110 and the ultrasonic vibrator 130 to 100 kHz or higher, a parametric speaker including the ultrasonic transducer 100 can reproduce audible sound only in a limited space.

[0055] In the ultrasonic transducer 100 according to the first embodiment of the present invention, when the sound velocity of the shear wave in the first diaphragm 110 is Cv, the sound velocity of the shear wave in the piezoelectric body 131 is Cp, the thickness dimension of the first diaphragm 110 is Tv, and the thickness dimension of the piezoelectric body 131 is Tp, the relationship 0.25CpTp / Cv≦Tv≦0.6CpTp / Cv is satisfied. This makes it possible to drive the ultrasonic transducer 100 in a state where the internal stress (a value normalized per sound pressure) in the third direction (Z-axis direction) generated in the ultrasonic transducer 100 is low. Consequently, it is possible to generate ultrasonic waves with high sound pressure while suppressing the generation of cracks due to internal stress at each of the joint between the first diaphragm 110 and the frame body 120 and the joint between the frame body 120 and the ultrasonic vibrator 130.

[0056] In the ultrasonic transducer 100 according to the first embodiment of the present invention, the relationship 0.7CpTp / Cv≦Tv≦1.3CpTp / Cv is satisfied, where Cv is the sound velocity of the shear wave in the first diaphragm 110, Cp is the sound velocity of the shear wave in the piezoelectric body 131, Tv is the thickness of the first diaphragm 110, and Tp is the thickness of the piezoelectric body 131. This allows the physical balance between the first diaphragm 110 and the ultrasonic vibrator 130 to be maintained during vibration, and increases the amplitude of the resonant vibration of the first diaphragm 110, thereby increasing the sound pressure and suppressing vibration leakage.

[0057] In the first modified example of the ultrasonic transducer 100 according to the first embodiment of the present invention, the ultrasonic vibrator is a unimorph piezoelectric vibrator, and a second diaphragm is provided on the side opposite to the frame side of the piezoelectric body 131. This makes it possible to maintain a high displacement of the first diaphragm 110 while reducing power consumption, thereby improving the efficiency of the ultrasonic transducer.

[0058] (Embodiment 2) An ultrasonic transducer according to a second embodiment of the present invention will be described below with reference to the drawings. The ultrasonic transducer according to the second embodiment of the present invention differs from the ultrasonic transducer according to the first embodiment of the present invention in that a plurality of ultrasonic vibrators are arranged in an array, and therefore, description of the same configuration as the ultrasonic transducer according to the first embodiment of the present invention will not be repeated.

[0059] Fig. 17 is a side view showing the configuration of an ultrasonic transducer according to embodiment 2 of the present invention, Fig. 18 is a rear view of the ultrasonic transducer shown in Fig. 17 as seen from the direction of arrow XVIII.

[0060] 17 and 18, in an ultrasonic transducer 200 according to embodiment 2 of the present invention, ultrasonic transducers 100 according to embodiment 1 arranged in an array in a first direction (X-axis direction) are integrally configured. The ultrasonic transducer 200 includes a first diaphragm 210, a plurality of frame bodies 220, and a plurality of ultrasonic vibrators 130. The plurality of frame bodies 220 are bonded to the first diaphragm 210, and the plurality of ultrasonic vibrators 130 are bonded to the plurality of frame bodies 220, respectively.

[0061] Here, we will explain the method for manufacturing the ultrasonic transducer 200. Fig. 19 is an exploded perspective view showing a stacked state in the process of stacking and bonding the components of the ultrasonic transducer according to the second embodiment of the present invention.

[0062] 19, first diaphragm 210 has a flat plate shape, and a plurality of slits 211 extending in a second direction (Y-axis direction) are formed at intervals in a first direction (X-axis direction). First diaphragm 210 is made of an aluminum alloy such as aluminum-containing duralumin, or a metal such as stainless steel. In this embodiment, first diaphragm 210 is made of stainless steel. The plurality of slits 211 are formed by etching, cutting, or the like.

[0063] Each of the multiple frame bodies 220 has a rectangular annular shape. Each of the multiple frame bodies 220 has a short side direction along a first direction (X-axis direction) and a long side direction along a second direction (Y-axis direction). Each of the multiple frame bodies 220 extends in the second direction (Y-axis direction). The axial direction of each of the multiple frame bodies 220 is along a third direction (Z-axis direction). Each of the multiple frame bodies 220 has a pair of long side portions 221 extending in the second direction (Y-axis direction) and a pair of short side portions 222 extending in the first direction (X-axis direction). The shortest distance between the long side portions 221 is four or more times the shortest distance between the short side portions 222.

[0064] The multiple frame bodies 220 are arranged side by side in a first direction (X-axis direction). A slit 223 is formed between adjacent frame bodies 220 in the first direction (X-axis direction). The multiple slits 223 are formed by etching, cutting, or the like. Adjacent long side portions 221 of adjacent frame bodies 220 in the first direction (X-axis direction) are separated from each other by the slits 223.

[0065] The frame bodies 220 adjacent to each other in the first direction (X-axis direction) are connected to each other at the short side portions 222. That is, among the plurality of frame bodies 220, the frame bodies 220 adjacent to each other in the short side direction are connected to each other at both ends in the longitudinal direction.

[0066] Each of the plurality of frame bodies 220 is formed from a metal such as an aluminum alloy or stainless steel, glass epoxy, resin, etc. In this embodiment, the plurality of frame bodies 220 are formed from a single thin plate, but this is not limiting, and the plurality of frame bodies 220, each formed from a plurality of thin plates, may be integrated by joining the short side portions 222 of the frame bodies 220 to each other.

[0067] In this embodiment, each of the plurality of ultrasonic vibrators 130 includes two stacked piezoelectric bodies 131. As shown in Fig. 19, the two piezoelectric bodies 131 constituting the plurality of ultrasonic vibrators 130 are stacked and joined in the form of two thin plates.

[0068] 20 is a plan view showing the positional relationship in the first direction (X-axis direction) in the step of cutting the piezoelectric body of the ultrasonic transducer according to Embodiment 2 of the present invention. In FIG. 20, only one piezoelectric body 131 is shown.

[0069] 20, the slits 211 and 223 are arranged at the same position in the first direction (X-axis direction) so as to overlap with each other in the third direction (Z-axis direction). The piezoelectric body 131 is cut and divided by a dicer or the like along a plurality of cut lines LC extending in the second direction (Y-axis direction) so as to overlap with the slits 211 and 223 in the third direction (Z-axis direction). As a result, the ultrasonic transducer 200 shown in FIGS. 17 and 18 is formed.

[0070] FIG. 21 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to the second embodiment of the present invention transmits or receives ultrasonic waves.

[0071] 21 , in first diaphragm 210, middle portion 210c located at the middle in the longitudinal direction inside each frame body 220 becomes the antinode of the resonant vibration, and end portion 210e located at both ends in the longitudinal direction inside each frame body 220 becomes the node of the resonant vibration. In other words, in first diaphragm 210, the portion located above the inner space of each frame body 220 becomes the vibration region that resonates. The longitudinal dimension of the vibration region of first diaphragm 210 is the same as the longitudinal dimension inside each frame body 220, and the lateral dimension of the vibration region of first diaphragm 210 is the same as the lateral dimension inside each frame body 220.

[0072] The ultrasonic transducer 100 according to the first embodiment has nodal points at both ends in the second direction (Y-axis direction), which is the longitudinal direction, and therefore even if the ultrasonic transducers 100 according to the first embodiment are connected to each other at the both ends to form an array to form the ultrasonic transducer 200 according to the second embodiment, the resonant vibration of each ultrasonic transducer 100 is not inhibited. Therefore, by increasing the number of ultrasonic transducers 100 that form the ultrasonic transducer 200 according to the second embodiment, the sound pressure level can be easily increased.

[0073] In a parametric speaker including the ultrasonic transducer 200 according to the second embodiment of the present invention, it is possible to modulate the ultrasonic waves emitted from the ultrasonic transducer 200 by modulating and driving the ultrasonic transducer 200, thereby reproducing audible sounds.

[0074] Here, the results of a simulation analysis using the finite element method on the relationship between the frequency of ultrasonic waves and the attenuation of the sound pressure level due to the propagation distance will be described. As the simulation analysis conditions, the finite element method was used to simulate and analyze the transition of attenuation due to the propagation distance of an audible sound with a frequency of 4 kHz reproduced from ultrasonic waves with a resonance frequency of 146 kHz transmitted from the ultrasonic transducer 200 according to this embodiment, and an audible sound with a frequency of 4 kHz reproduced from ultrasonic waves with a resonance frequency of 40 kHz transmitted from the ultrasonic element array according to the second comparative example.

[0075] Fig. 22 is a perspective view showing the configuration of an ultrasonic element array according to Comparative Example 2. As shown in Fig. 22, in the ultrasonic element array according to Comparative Example 2, 50 ultrasonic elements 900 are arranged in a matrix at intervals.

[0076] Fig. 23 is a graph showing actual measurements of the transition of attenuation of sound pressure level over propagation distance in the ultrasonic transducer according to this embodiment and the ultrasonic transducer according to the second comparative example. In Fig. 23, the vertical axis represents sound pressure level (dB) and the horizontal axis represents propagation distance (cm). The solid line represents data for the ultrasonic transducer 200 according to this embodiment, and the dotted line represents data for the ultrasonic transducer according to the second comparative example. The sound pressure level is a value normalized by setting the sound pressure level of an audible sound with a frequency of 4 kHz at a point 30 cm away in the third direction (Z-axis direction) from the front of each of the ultrasonic transducer and the ultrasonic element array to 0 dB.

[0077] 23, the audible sound reproduced from the ultrasonic waves having a resonance frequency of 146 kHz transmitted from the ultrasonic transducer 200 according to this embodiment was attenuated more due to the propagation distance than the audible sound reproduced from the ultrasonic waves having a resonance frequency of 40 kHz transmitted from the ultrasonic element array according to the second comparative example. This is because high-frequency ultrasonic waves are easily absorbed by the air as heat, and therefore the audible sound reproduced using high-frequency ultrasonic waves as a carrier wave is attenuated more due to the propagation distance.

[0078] As described above, a parametric speaker including the ultrasonic transducer 200 according to this embodiment, which transmits ultrasonic waves with high frequencies of 100 kHz or higher, can suppress sound from traveling unnecessarily far and suppress sound leakage due to unnecessary reflections, thereby reproducing audible sound only in a limited space. Furthermore, the ultrasonic transducer 200 can increase the attenuation of audible sound over the propagation distance without providing a configuration for transmitting an opposite-phase carrier wave as in Patent Document 2, allowing for a simple and compact configuration. Furthermore, because ultrasonic waves with high frequencies of 100 kHz or higher are outside the audible range of animals such as dogs and cats, the effects on these animals can be suppressed.

[0079] As shown in Figure 23, in order for audible sound to attenuate after a propagation distance of 30 cm, the Rayleigh distance must be kept within 30 cm. The Rayleigh distance R0 is given by R0 = (k × a 2 ) / 2, where k is the wave number and a is the radius of the sound source. Therefore, if the speed of sound in air is 340 m / s, when the ultrasonic frequency is 100 kHz, the longitudinal dimension of the vibration region of first diaphragm 210 is 36 mm or less, when the ultrasonic frequency is 150 kHz, the longitudinal dimension of the vibration region of first diaphragm 210 is 29.4 mm or less, and when the ultrasonic frequency is 200 kHz, the longitudinal dimension of the vibration region of first diaphragm 210 is 25.5 mm or less. When the ultrasonic frequency is 100 kHz or more, the longitudinal dimension L1 is between 4 and 24 times the lateral dimension L2.

[0080] The ultrasonic transducer 200 according to this embodiment can be used as a phased array system.

[0081] 24 is a side view showing a state in which an ultrasonic transducer according to a modification of this embodiment constituting a phased array system transmits ultrasonic waves in a plane in the third direction (Z-axis direction). As shown in FIG. 24, an ultrasonic transducer 200a according to a modification of this embodiment includes a processing circuit 240 capable of controlling the timing of transmitting ultrasonic waves from each of the ultrasonic transducers A to G.

[0082] Fig. 25 is a diagram showing the drive start delay time in the first state in which the processing circuit synchronizes the ultrasonic wave transmission timings of the ultrasonic transducers A to G. As shown in Fig. 25, in the first state in which the processing circuit 240 synchronizes the ultrasonic wave transmission timings of the ultrasonic transducers A to G, ultrasonic waves Da are transmitted in a plane in the third direction (Z-axis direction) as shown in Fig. 24.

[0083] 26 is a side view showing a state in which an ultrasonic transducer according to a modified example of this embodiment transmits ultrasonic waves in a plane in an oblique direction inclined toward the first direction (X-axis direction) with respect to the third direction (Z-axis direction). FIG. 27 is a diagram showing a drive start delay time in a second state in which ultrasonic waves are transmitted in the order of ultrasonic transducers G to A by the processing circuit. As shown in FIG. 27, in the second state in which the drive start delay time is increased in the order of ultrasonic transducers G to A by the processing circuit 240, 6 As shown in FIG. 1, ultrasonic waves Db are emitted in a plane in a direction oblique to the first direction (X-axis direction) with respect to the third direction (Z-axis direction).

[0084] Fig. 28 is a side view showing a state in which an ultrasonic transducer according to a modified example of this embodiment transmits ultrasonic waves in the third direction (Z-axis direction) so as to concentrate at the center in the first direction (X-axis direction). Fig. 29 is a diagram showing the drive start delay time in a third state in which the processing circuit transmits ultrasonic waves in the order of ultrasonic transducers A to D and ultrasonic transducers G to D. As shown in Fig. 29, in the third state in which the processing circuit 240 increases the drive start delay time in the order of ultrasonic transducers A to D and ultrasonic transducers G to D, ultrasonic waves Dc are transmitted in the third direction (Z-axis direction) so as to concentrate at the center in the first direction (X-axis direction) of the ultrasonic transducer 200a, as shown in Fig. 28.

[0085] In the ultrasonic transducer 200 according to the second embodiment of the present invention, at least one frame body 220 is arranged in a plurality of rows in the short-side direction and joined to the first diaphragm 210, and adjacent frame bodies 220 in the short-side direction of at least one frame body 220 are connected to each other at both ends in the long-side direction. This makes it possible to easily increase the sound pressure level.

[0086] The ultrasonic transducer 200a according to the modified example of the second embodiment of the present invention can function as a phased array system.

[0087] (Addendum) It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0088] <1> A first diaphragm; At least one frame extending in a longitudinal direction and joined to the first diaphragm; at least one ultrasonic vibrator attached to each of the at least one frame body and facing the first diaphragm with a gap therebetween; the first vibration plate resonates in an opposite phase to the at least one ultrasonic transducer in a direction perpendicular to the first vibration plate, An ultrasonic transducer, wherein the longitudinal dimension inside the at least one frame body is four or more times the lateral dimension inside the at least one frame body that is perpendicular to the longitudinal direction.

[0089] <2> The at least one ultrasonic transducer is a piezoelectric element including a piezoelectric body. <1> 2. The ultrasonic transducer according to claim 1 .

[0090] <3> The resonance frequency of the first diaphragm and the at least one ultrasonic vibrator is 100 kHz or more. <1> or <2> 2. The ultrasonic transducer according to claim 1 .

[0091] <4> When the sound velocity of the shear wave of the first diaphragm is Cv, the sound velocity of the shear wave of the piezoelectric body is Cp, the thickness dimension of the first diaphragm is Tv, and the thickness dimension of the piezoelectric body is Tp, The relationship 0.25CpTp / Cv≦Tv≦0.6CpTp / Cv is satisfied. <2> 2. The ultrasonic transducer according to claim 1 .

[0092] <5> When the sound velocity of the shear wave of the first diaphragm is Cv, the sound velocity of the shear wave of the piezoelectric body is Cp, the thickness dimension of the first diaphragm is Tv, and the thickness dimension of the piezoelectric body is Tp, The relationship 0.7CpTp / Cv≦Tv≦1.3CpTp / Cv is satisfied. <2> 2. The ultrasonic transducer according to claim 1 .

[0093] <6> a plurality of the at least one frame members are arranged in the short-side direction and joined to the first diaphragm; The at least one frame body has two adjacent frame bodies in the short side direction connected to each other at both ends in the long side direction. <1> from <5> 10. The ultrasonic transducer according to claim 9, wherein the ultrasonic transducer is a piezoelectric element.

[0094] <7> the at least one ultrasonic transducer is a unimorph type piezoelectric transducer, A second vibration plate is provided on the opposite side of the piezoelectric body from the frame body side. <2> 2. The ultrasonic transducer according to claim 1 .

[0095] In the above-described embodiments, configurations that can be combined may be combined with each other.

[0096] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0097] 100, 100a, 200, 200a ultrasonic transducer, 110, 210 first vibration plate, 110c, 210c intermediate portion, 110e, 210e end portion, 120, 120a, 220 frame body, 121, 221 long side portion, 122, 222 short side portion, 130, 130a, 130b, 130c ultrasonic vibrator, 131 piezoelectric body, 132 first electrode, 133 second electrode, 134 intermediate electrode, 135 second vibration plate, 140, 240 processing circuit, 211, 223 slit, 800, 900 ultrasonic element.

Claims

1. A first diaphragm; At least one frame body extending in a longitudinal direction and having one axial end joined to the first diaphragm; at least one ultrasonic vibrator attached to the other end of the at least one frame body in the axial direction, facing the first vibration plate at an interval with an internal space of the at least one frame body sandwiched therebetween; the first vibration plate vibrates in a direction perpendicular to the first vibration plate in an antiphase with the at least one ultrasonic vibrator; a longitudinal dimension of the at least one frame body on an inner side thereof is four times or more a lateral dimension of the at least one frame body on an inner side thereof that is perpendicular to the longitudinal direction, An ultrasonic transducer, wherein the axial direction of the at least one frame body is perpendicular to both the longitudinal direction and the lateral direction.

2. The ultrasonic transducer according to claim 1 , wherein the at least one ultrasonic vibrator is a piezoelectric element including a piezoelectric body.

3. The ultrasonic transducer of claim 1 , wherein the first diaphragm and the at least one ultrasonic vibrator have a resonant frequency of 100 kHz or higher.

4. When the sound velocity of the shear wave of the first diaphragm is Cv, the sound velocity of the shear wave of the piezoelectric body is Cp, the thickness dimension of the first diaphragm is Tv, and the thickness dimension of the piezoelectric body is Tp, 3. The ultrasonic transducer according to claim 2, wherein the relationship 0.25CpTp / Cv≦Tv≦0.6CpTp / Cv is satisfied.

5. When the sound velocity of the shear wave of the first diaphragm is Cv, the sound velocity of the shear wave of the piezoelectric body is Cp, the thickness dimension of the first diaphragm is Tv, and the thickness dimension of the piezoelectric body is Tp, 3. The ultrasonic transducer according to claim 2, wherein the relationship 0.7CpTp / Cv≦Tv≦1.3CpTp / Cv is satisfied.

6. a plurality of the at least one frame members are arranged in the short-side direction and joined to the first diaphragm; 6. The ultrasonic transducer according to claim 1, wherein adjacent frame members in the short-side direction of the at least one frame member are connected to each other at both ends in the long-side direction.

7. the at least one ultrasonic transducer is a unimorph type piezoelectric transducer, 3. The ultrasonic transducer according to claim 2, further comprising a second diaphragm provided on the side of said piezoelectric body opposite to the frame body side.

8. 2. The ultrasonic transducer of claim 1, wherein the first vibration plate has an intermediate portion located at the middle of the longitudinal direction inside the at least one frame body that serves as an antinode of the resonant vibration, and ends located at both ends of the longitudinal direction inside the at least one frame body that serve as nodes of the resonant vibration.

9. The ultrasonic transducer according to any one of claims 1 to 5, 7 and 8 is provided, A parametric speaker that reproduces audible sound by modulating the ultrasonic transducer.

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