Sound generating device

Abstract

To provide a small and lightweight sound generation device that can generate high-output sound in a low frequency band.SOLUTION: A sound generation device according to an embodiment includes a vibrating body, a holding portion, and a fixing portion. The holding portion holds the vibrating body. The fixing portion fixes the holding portion. The rigidity of the fixing portion is smaller than the rigidity of the holding portion.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a sound generating device.

Background Art

[0002] In recent years, sound sources that can generate high-power sound in the low-frequency band, such as noise control devices and acoustic playback devices, have been widely used. As such a sound source, a dedicated speaker that excels in low-frequency reproduction, such as a woofer, is usually used. However, a sound source that excels in low-frequency reproduction is generally large and heavy, and there is a strong demand for miniaturization and weight reduction from the viewpoint of expanding the application range.

[0003] As a small and lightweight sound source, a sound generating device using a piezoelectric vibrator (such as a piezoelectric speaker or a piezoelectric buzzer) has been developed mainly for portable electronic devices such as mobile phones and tablet terminals. However, usually, as miniaturization and weight reduction progress, the resonance frequency increases, so it is considered unsuitable for low-frequency reproduction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a small and lightweight sound generating device that can generate high-power sound in the low-frequency band.

Means for Solving the Problems

[0006] The sound generating device according to one embodiment includes a vibrating body, a holding part, and a fixing part. The holding part holds the vibrating body. The fixing part fixes the holding part. The rigidity of the fixing part is smaller than the rigidity of the holding part.

Brief Description of the Drawings

[0007]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0008] Hereinafter, embodiments will be described with reference to the drawings. In some of the drawings, illustration of one or more components is omitted.

[0009] [First Embodiment] FIG. 1, FIG. 2, FIG. 3, and FIG. 4 are a perspective view, a front view, a side view, and an exploded perspective view schematically showing a sound generating device 10 according to the first embodiment. As shown in FIGS. 1 to 4, the sound generating device 10 includes a vibrating body 11, a holding portion 12, and a fixing portion 13.

[0010] The vibrating body 11 is a small and lightweight vibration device. The vibration device receives an electrical signal (for example, a voltage signal) from an electrical circuit (not shown) and vibrates to generate sound corresponding to the vibration. As the vibrating body 11, for example, a piezoelectric vibrator can be used.

[0011] FIGS. 5A and 5B schematically show a piezoelectric vibrator 50 which is an example of a piezoelectric vibrator that can be used as the vibrating body 11. As shown in FIGS. 5A and 5B, the piezoelectric vibrator 50 is a bimorph-type piezoelectric vibrator in which piezoelectric elements 51 are attached to both surfaces of a circular metal plate 52. It is also possible to use a unimorph-type piezoelectric vibrator in which a piezoelectric element is attached to one side of a metal plate, a laminated-type piezoelectric vibrator in which piezoelectric elements are stacked, and the like.

[0012] Referring to FIGS. 1 to 4 again, the holding portion 12 holds the vibrating body 11. In the present embodiment, the holding portion 12 is a two-part metal annular holder that holds the periphery of the vibrating body 11 in surface contact. Specifically, the holding portion 12 includes a pair of holding members 121 and 122 that are made of metal and have an annular shape, and holds the vibrating body 11 by sandwiching the periphery of the vibrating body 11 with the holding members 121 and 122.

[0013] Note that the holding portion 12 shown in FIGS. 1 to 4 is an example, and the configuration of the holding portion 12 is not limited to the above-described configuration. For example, the holding portion 12 may be a single holding member corresponding to a member in which the above-described holding members 121 and 122 are integrally formed.

[0014] The fixing part 13 fixes the holding part 12. In the present embodiment, the fixing part 13 is a two-part resin annular holder that holds the both end faces of the holding part 12 in between. Specifically, the fixing part 13 includes a pair of fixing members 131 and 132 that are made of resin and have an annular shape, all screws (sectioned bolts) 133, and nuts 134. The resin is an example of an elastic material. The rigidity of the fixing part 13 (specifically, the fixing members 131 and 132) is smaller (lower) than the rigidity of the holding part 12. The fixing members 131 and 132 are fastened by all screws 133 and nuts 134 arranged along the axial direction of the sound generating device 10 (that is, parallel to the Z axis shown in FIGS. 2 to 4). Here, the axial direction of the sound generating device 10 is a direction orthogonal to the main surface of the vibrating body 11. The fixing members 131 and 132 have holes 135. With the holding part 12 placed between the fixing members 131 and 132, all screws 133 are inserted into the holes 135 of the fixing members 131 and 132, and nuts 134 are screwed onto both sides of each all screw 133. By screwing the nuts 134, a clamping force is generated along the axial direction of the sound generating device 10, and the fixing part 13 supports the holding part 12 by the clamping force. Thereby, the holding part 12 is elastically supported (softly supported) by the fixing part 13, and thus, the vibrating body 11 is elastically supported.

[0015] Note that the fixing part 13 shown in FIGS. 1 to 4 is an example, and the configuration of the fixing part 13 is not limited to the above-described configuration. For example, the fixing part 13 may have any configuration as long as it elastically supports the holding part 12. Elastic support means a support method that allows displacement in the axial direction of the sound generating device 10 of the holding part 12.

[0016] The shapes of the respective components shown in FIGS. 1 to 4 are examples, and the shapes of the respective components are not limited thereto. For example, the vibrating body 11, the holding part 12, and the fixing part 13 may be polygonal.

[0017] In the sound generating device 10, as shown in FIG. 6, in order to shift the resonance frequency of the sound generating device 10 to a lower frequency range, a load weight 14 may be attached to the vibrating body 11. The load weight 14 is provided to add mass to the vibrating body 11. For example, the load weight 14 includes a resin screw 141 and one or more resin nuts 142 (two resin nuts 142 in this example). A hole is provided at the center of the vibrating body 11, the resin screw 141 is inserted into the hole of the vibrating body 11, and the resin nut 142 is screwed onto the resin screw 141.

[0018] As shown in FIG. 7, the load weight 14 may further include one or more metal nuts 143 (three metal nuts 143 in this example) in order to increase the mass added to the vibrating body 11. The metal nut 143 is screwed onto the resin screw 141 after the resin nut 142.

[0019] The load weight 14 shown in FIG. 6 or FIG. 7 is an example, and the configuration of the load weight 14 attached to the vibrating body 11 is not limited to the configuration shown in FIG. 6 or FIG. 7. For example, in the configuration shown in FIG. 6, a metal screw may be used instead of the resin screw 141. Also, instead of the combination of screw and nut, the load weight 14 may be an elastic member such as a rubber plate.

[0020] Next, while referring to FIG. 8, an overview of the proof-of-concept test of the method (proposed method) according to this embodiment will be described. In this test, a sweep signal (500 Hz ≤ f ≤ 3 kHz) amplified by an amplifier (class-D amplifier) was input to the sound generator 10 to drive the sound generator 10, and the axial vibration velocity at the vibration observation point located approximately at the center of the vibrating body 11 and the radiated sound pressure at the sound pressure observation point located at a predetermined distance from the surface of the vibrating body 11 were measured. A laser Doppler vibrometer (LDV) was used to measure the vibration velocity, and a microphone was used to measure the sound pressure. The vibrating body 11 used a bimorph vibrator including a metal plate (aluminum alloy) and piezoelectric elements (lead zirconate titanate (PZT)) provided on both surfaces of the metal plate. The outer diameter Ro of the vibrating body 11 was 45 mm, and a hole (inner diameter Ri: 3 mm) was provided at the center of the vibrating body 11. The hole was used to attach the load weight 14 to the vibrating body 11. The first resonance frequency of the vibrating body 11 in free support was approximately 1.3 kHz. Free support means a support method that allows translational displacement and rotational displacement of the vibrating body 11. The holding part 12 used a two-part metal ring holder (aluminum alloy), and the fixing part 13 used a two-part resin ring holder (ABS: Acrylonitrile Butadiene Styrene).

[0021] FIGS. 9 and 10 show the results of the proof-of-concept test of the proposed method. Specifically, FIG. 9 shows the frequency characteristics of the axial vibration velocity of the vibrating body 11 measured by the above method, and FIG. 10 shows the frequency characteristics of the radiated sound pressure measured by the above method. FIGS. 9 and 10 also show the results of the test on the sound generator according to the comparative example. The sound generator according to the comparative example is obtained by removing the holding part 12 from the sound generator 10 according to this embodiment. That is, in the sound generator according to the comparative example, the vibrating body 11 is directly supported by the fixing part 13, and the vibrating body 11 is supported more rigidly than in the proposed method.

[0022] As shown in FIGS. 9 and 10, while the resonance frequency of the sound generating device according to the comparative example is about the first resonance frequency of the vibrating body 11, the resonance frequency of the sound generating device 10 according to the present embodiment is about 1000 Hz lower than the first resonance frequency of the vibrating body 11. Therefore, it can be seen that by holding the vibrating body 11 via the holding portion 12, it is possible to shift the resonance frequency to a lower frequency range. Further, it can be seen that the sound generating device 10 according to the present embodiment has a wider resonance peak width than the sound generating device according to the comparative example and can reproduce a wider band of bass sounds.

[0023] Furthermore, a test was conducted to verify the effect of adding mass to the vibrating body 11. The addition of mass to the vibrating body 11 was carried out by the method described with reference to FIGS. 6 and 7, and the axial vibration velocity and the radiated sound pressure of the vibrating body 11 were measured in the same manner as described above.

[0024] FIG. 11 shows the frequency characteristics of the axial vibration velocity of the vibrating body 11 measured by the above method, and FIG. 12 shows the frequency characteristics of the radiated sound pressure measured by the above method. In each of FIGS. 11 and 12, the results of four cases are shown: (a) without load weight, (b) resin screw (PB) × 1 & resin nut (PN) × 2, (c) resin screw × 1 & resin nut × 2 & metal nut (MN) × 2, and (d) resin screw × 1 & resin nut × 2 & metal nut × 4. From FIGS. 11 and 12, it can be seen that as the mass added to the vibrating body 11 increases, the resonance frequency of the sound generating device 10 shifts to a lower frequency range.

[0025] As described above, the sound generating device 10 includes a vibrating body 11, a holding portion 12 that holds the vibrating body 11, and a fixing portion 13 that fixes the holding portion 12 so as to elastically support the holding portion 12. For example, by configuring the rigidity of the fixing portion 13 to be smaller than the rigidity of the holding portion 12, the fixing portion 13 can elastically support the holding portion 12. In this configuration, the vibrating body 11 is elastically supported via the holding portion 12. Thereby, the resonance frequency of the sound generating device 10 shifts to a lower frequency range. As a result, even in a small and lightweight device, high-output bass reproduction becomes possible.

[0026] The sound generating device 10 may further include a load weight 14 attached to the vibrating body 11 in order to add mass to the vibrating body 11. In this configuration, the resonance frequency of the sound generating device 10 can be shifted to a lower frequency range.

[0027] [Second Embodiment] FIGS. 13, 14, 15, and 16 are a front view, a side view, a cross-sectional view, and an exploded perspective view schematically showing a sound generating device 20 according to the second embodiment. FIG. 15 shows a cross-section of the sound generating device 20 taken along line A-A′ shown in FIG. 13. As shown in FIGS. 13 to 16, the sound generating device 20 includes a vibrating body 21, a holding portion 22, a support portion 23, and a fixing portion 24.

[0028] The vibrating body 21 is the same as the vibrating body 11 of the sound generating device 10 according to the first embodiment. Therefore, the description of the vibrating body 21 is omitted.

[0029] The holding portion 22 is the same as the holding portion 12 of the sound generating device 10 according to the first embodiment. Specifically, the holding portion 22 includes a pair of holding members 221 and 222 that hold the periphery of the vibrating body 21 in surface contact. Each of the holding members 221 and 222 has a plurality of screw holes 223. The screw holes 223 extend along the radial direction of the sound generating device 20. In each of the holding members 221 and 222, the screw holes 223 are provided discretely in the circumferential direction of the sound generating device 20. In the example shown in FIGS. 13 to 16, in each of the holding members 221 and 222, eight screw holes 223 are provided at an angular interval of 45°.

[0030] The support portion 23 supports the holding portion 22, and the fixing portion 24 fixes the support portion 23. The rigidity of the support portion 23 is smaller than that of the holding portion 22. In the present embodiment, the support portion 23 includes a plurality of metal screws 231 as elastic members, and the fixing portion 24 is a two-part metal ring holder having a plurality of screw holes. The fixing portion 24 includes a pair of fixing members 241, 242 made of metal and having an annular shape and a plurality of metal screws 243. Each of the fixing members 241, 242 is provided with a plurality of screw holes 244 and a plurality of screw holes 245. Metal is an example of an elastic material. The screw holes 244 extend along the axial direction (Z-axis) of the sound generating device 20, and the metal screws 243 are screwed into the screw holes 244. The fixing members 241, 242 are fastened with the metal screws 243. The screw holes 245 extend along the radial direction of the sound generating device 20, and the metal screws 231 are screwed into the screw holes 245. In each of the fixing members 241, 242, the screw holes 245 are provided discretely in the circumferential direction. In the example shown in FIGS. 13 to 16, in each of the fixing members 241, 242, eight screw holes 245 are provided at an angular interval of 45°.

[0031] The inner diameters of the fixing members 241, 242 are slightly larger than the outer diameters of the holding members 221, 222. With the screw holes 245 of the fixing member 241 facing the screw holes 223 of the holding member 221, the fixing member 241 is disposed outside the holding member 221, and the metal screws 231 are screwed into the screw holes 245 of the fixing member 241 and the screw holes 223 of the holding member 221. With the screw holes 245 of the fixing member 242 facing the screw holes 223 of the holding member 222, the fixing member 242 is disposed outside the holding member 222, and the metal screws 231 are screwed into the screw holes 245 of the fixing member 242 and the screw holes 223 of the holding member 222. The metal screws 231 are discretely arranged along the outer circumference of the holding portion 22. In the example shown in FIGS. 13 to 16, eight metal screws 231 are arranged at an angular interval of 45° outside the holding member 221, and eight metal screws 231 are arranged at an angular interval of 45° outside the holding member 222. By connecting the metal screws 231 to the outer circumference of the holding portion 22, beam-like elastic support becomes possible.

[0032] Note that the support portion 23 shown in FIGS. 13 to 16 is an example, and the configuration of the support portion 23 is not limited to the above-described configuration. The support portion 23 may be a plurality of resin screws or a film-like elastic member (e.g., a rubber sheet). When the support portion 23 is a rubber sheet, the support portion 23 is disposed between the holding portion 22 and the fixing portion 24.

[0033] The shape of each component shown in FIGS. 13 to 16 is an example and is not limited thereto. For example, the vibrating body 21, the holding portion 22, and the fixing portion 24 may be polygonal.

[0034] Furthermore, in order to shift the resonance frequency of the sound generating device 20 to a lower frequency range, a load weight may be attached to the vibrating body 21.

[0035] As shown in FIGS. 17 and 18, the sound generating device 20 may further include an installation portion 25 for installing the sound generating device 20 on an arbitrary structure (e.g., a resonance chamber). In the examples shown in FIGS. 17 and 18, the installation portion 25 includes a base member 251 and frame members 252, 253. The base member 251 has a hole 254 at its center and a plurality of holes 255 around the hole 254. The diameter of the hole 254 is slightly larger than the outer diameter of the holding portion 22. The base member 251 is disposed between the fixing members 241, 242 of the fixing portion 24 and is attached to the fixing portion 24. In a state where the base member 251 is attached to the fixing portion 24, the vibrating body 21 is positioned in the hole 254. A metal screw 243 is inserted through the hole 255. The base member 251 is made of, for example, an elastic material. As the base member 251, for example, a rubber sheet can be used. The rigidity of the installation portion 25 (specifically, the base member 251) is smaller than the rigidity of the fixing portion 24 (specifically, the fixing members 241, 242).

[0036] Each of the frame members 252 and 253 has a hole 256 at its center. The diameter of the hole 256 is slightly larger than the outer diameters of the fixing members 241 and 242. The base member 251 is disposed between the frame members 252 and 253 and is attached to the frame members 252 and 253 using, for example, a combination of a screw and a nut. In a state where the base member 251 is attached to the frame members 252 and 253, the holding member 221 and the fixing member 241 are positioned in the hole 256 of the frame member 252, and the holding member 222 and the fixing member 242 are positioned in the hole 256 of the frame member 253. The frame members 252 and 253 may be any frame that can be attached to the structure. For example, a metal frame can be used as the frame members 252 and 253.

[0037] As shown in FIGS. 19 and 20, the sound generating device 20 may further include a resonance chamber 26 having a resonance frequency substantially equal to the natural frequency of the vibrating body 21 in order to increase the radiated sound pressure at the resonance frequency of the sound generating device 20. That the resonance frequency of the resonance chamber 26 is substantially equal to the natural frequency of the vibrating body 21 means that the resonance frequency of the resonance chamber 26 is within a frequency range of 200 Hz centered on the natural frequency of the vibrating body 21. If the natural frequency of the vibrating body 21 is f Hz, the resonance frequency of the resonance chamber 26 is set within a frequency range from (f - 100) Hz to (f + 100) Hz.

[0038] Note that the configuration of the installation portion 25 is not limited to the above-described configuration. For example, the base member 251 may be omitted, and the fixing portion 24 (specifically, the fixing members 241 and 242) may be attached to the frame members 252 and 253.

[0039] The vibrating body 21, the holding part 22, the supporting part 23, and the fixing part 24 are arranged in the resonance chamber 26 and are attached to the resonance chamber 26 via the installation part 25. The resonance chamber 26 includes a housing 261, 262 and a plate 263. The housings 261, 262 form an internal space in which the vibrating body 21, the holding part 22, the supporting part 23, and the fixing part 24 are arranged. The housings 261, 262 are fastened, for example, with screws. The housing 262 is provided with an opening 264 that communicates the internal space with the external space, and the plate 263 is attached to the opening 264 of the housing 262. The plate 263 has a sound radiation port 265 for radiating the sound emitted by the vibrating body 21 to the external space. The shapes of the housings 261, 262 and the plate 263 are designed such that the resonance frequency of the resonance chamber 26 is substantially equal to the natural vibration frequency of the vibrating body 21.

[0040] The installation part 25 and / or the resonance chamber 26 can also be applied to the sound generating device 10 according to the first embodiment.

[0041] A test was conducted to verify the effectiveness of the configuration of the sound generating device 20 shown in FIGS. 17 and 18. In the test, the axial vibration velocity of the vibrating body 21 and the radiated sound pressure from the vibrating body 21 were measured in the same manner as described in the first embodiment. As the vibrating body 21, a bimorph vibrator including a metal plate (aluminum alloy) and piezoelectric elements (lead zirconate titanate (PZT)) provided on both surfaces of the metal plate was used. The outer diameter Ro of the vibrating body 21 was set to 45 mm. A hole (inner diameter Ri: 3 mm) was provided at the center of the vibrating body 21. As the holding part 22, a two-part metal ring holder (aluminum alloy) was used, as the supporting part 23, a screw (stainless steel) was used, as the fixing part 24, a two-part metal ring holder (aluminum alloy) was used, and as the installation part 25, a rubber sheet (silicon, hardness: Shore A50) and a metal frame (aluminum alloy) were used. Further, in the same manner as described in the first embodiment, a load weight was attached to the vibrating body 21. That is, a resin screw was inserted into the hole provided at the center of the vibrating body 21, and a resin nut was screwed onto the resin screw to attach an additional weight to the vibrating body 21. When increasing the mass added to the vibrating body 21, a metal nut was added after the resin nut.

[0042] FIG. 21 shows the frequency characteristics of the axial vibration velocity of the vibrating body 21 measured by the above method, and FIG. 22 shows the frequency characteristics of the radiated sound pressure measured by the above method. In each of FIGS. 21 and 22, four results are shown: (a) without load weight, (b) resin screw × 1 & resin nut × 2, (c) resin screw × 1 & resin nut × 2 & metal nut × 2, and (d) resin screw × 1 & resin nut × 2 & metal nut × 4. As shown in FIGS. 21 and 22, the resonance frequency of the sound generating device 20 is lower than the first resonance frequency of the vibrating body 21. Therefore, according to the above-described configuration of the sound generating device 20, it is possible to shift the resonance frequency to a lower frequency range. Further, from FIGS. 21 and 22, it can be seen that as the mass added to the vibrating body 21 increases, the resonance frequency of the sound generating device 20 shifts to a lower frequency range. However, the radiated sound pressure decreases as the mass added to the vibrating body 21 increases.

[0043] Next, a test was conducted to verify the effectiveness of the resonance chamber 26. The test was conducted by the method shown in FIG. 23. Specifically, the radiated sound pressure at a sound pressure observation point located at a predetermined distance from the sound radiation port 265 of the resonance chamber 26 was measured with a microphone. Also, a load weight (resin screw × 1 & resin nut × 2 & metal nut × 4) was attached to the vibrating body 21.

[0044] FIG. 24 shows the frequency characteristics of the radiated sound pressure measured by the above method. In FIG. 24, four results are shown: (a) without resonance chamber, reference voltage applied, (b) with resonance chamber, reference voltage applied, (c) with resonance chamber, voltage twice the reference voltage applied, and (d) with resonance chamber, voltage four times the reference voltage applied. From FIG. 24, it can be seen that by providing the resonance chamber 26, the radiated sound pressure at the resonance frequency of the sound generating device 20 increases. Further, it can be seen that the radiated sound pressure increases linearly with respect to the voltage applied to the vibrating body 21.

[0045] As described above, the sound generating device 20 includes a vibrating body 21, a holding portion 22 that holds the vibrating body 21, a supporting portion 23 that elastically supports the holding portion 22, and a fixing portion 24 that fixes the supporting portion 23. For example, by configuring the rigidity of the supporting portion 23 to be smaller than the rigidity of the holding portion 22, the supporting portion 23 can elastically support the holding portion 22. In this configuration, the vibrating body 21 is elastically supported via the holding portion 22. Thereby, the resonance frequency of the sound generating device 20 shifts to a lower frequency range. As a result, even in a small and lightweight device, high-output bass reproduction becomes possible.

[0046] The supporting portion 23 and the fixing portion 24 are disposed outside the holding portion 22. For example, the supporting portion 23 may be an elastic member (e.g., a metal screw) discretely arranged along the outer periphery of the holding portion 22. Thereby, the device can be made thinner. Specifically, it becomes possible to reduce the axial dimension of the sound generating device 20.

[0047] The sound generating device 20 may further include an installation portion 25. Thereby, it becomes easier to attach the sound generating device 20 to a structure.

[0048] The sound generating device 20 may further include a resonance chamber 26 having a resonance frequency substantially equal to the natural frequency of the vibrating body 21. Thereby, it becomes possible to generate the sound at the resonance frequency of the sound generating device 20 with higher output.

[0049] The sound generating device 20 may further include a load weight attached to the vibrating body 21 in order to add mass to the vibrating body 21. In this configuration, the resonance frequency of the sound generating device 20 can be shifted to a lower frequency range.

[0050] [Third Embodiment] In the first and second embodiments, the resonance frequency of the sound generating device is shifted to a lower frequency range by configuring the holding portion that holds the vibrating body to be elastically supported. Shifting the resonance frequency of the sound generating device to a lower frequency range can also be implemented by the method described below. The method described in the third embodiment may be used alone or in combination with the methods described in the first and / or second embodiments.

[0051] It is known that the coupling state between two objects affects the stiffness of the system. This stiffness is called contact stiffness, and the material of the contact surface, surface roughness, contact area, etc. contribute to the contact stiffness. In the sound generating device according to the embodiment (for example, the sound generating device 10 or the sound generating device 20), the contact stiffness between the vibrating body and the holding portion affects the natural vibration frequency of the vibrating body. Therefore, by adjusting (specifically, decreasing) the contact stiffness between the vibrating body and the holding portion, it is possible to shift the resonance frequency of the sound generating device to a lower frequency range.

[0052] As methods for adjusting the contact stiffness, for example, the following three methods can be mentioned. (1) Change of the material of the holding portion (2) Change of the surface roughness of the holding portion (3) Change of the contact area between the vibrating body and the holding portion In method (1), as the material of the holding portion, a material with a lower stiffness than the material of the vibrating body (for example, an elastic material such as resin) is used. For example, when the vibrating body is a bimorph type piezoelectric vibrator as shown in FIG. 5, the holding portion holds a metal plate. The holding portion is made of a material with a lower stiffness than the stiffness of the material of the metal plate.

[0053] In method (2), in the contact area between the vibrating body and the holding portion, the surface roughness of the holding portion is made rougher than the surface roughness of the vibrating body. In other words, the surface roughness of the area of the holding portion that contacts the vibrating body is rougher than the surface roughness of the area of the vibrating body that contacts the holding portion.

[0054] In method (3), in the contact region between the vibrating body and the holding part, the surface area of the holding part is made smaller than the surface area of the vibrating body. In other words, the surface area of the region of the holding part that contacts the vibrating body is smaller than the surface area of the region of the vibrating body that contacts the holding part. An example of a method of making the surface area of the holding part smaller than the surface area of the vibrating body in the contact region between the vibrating body and the holding part is, as shown in FIGS. 25A and 25B, to form the surface shape of the holding part (for example, each of the holding members 121 and 122 shown in FIG. 1 or each of the holding members 221 and 222 shown in FIG. 16) into a comb-tooth shape. FIG. 25B shows a cross section of the holding member along the line B-B′ shown in FIG. 25A. A plurality (12 in this example) of concave portions with a thickness t are provided on the surface of the holding member.

[0055] FIGS. 26 and 27 show the results of a test for verifying the effectiveness of making the surface shape of the holding part into a comb-tooth shape. For the test, a holding part 22 of the sound generating device 20 shown in FIGS. 13 to 16 with its surface shape formed into a comb-tooth shape was used. FIG. 26 shows the frequency characteristics of the axial vibration velocity of the vibrating body 21, and FIG. 27 shows the frequency characteristics of the radiated sound pressure from the sound generating device 20. In each of FIGS. 26 and 27, the results for three cases are shown: (a) flat surface, (b) 12 comb teeth (t: 1 mm, θ: 10°, φ: 20°), and (c) 6 comb teeth (t: 1 mm, θ: 50°, φ: 20°). From FIGS. 26 and 27, it can be seen that by making the holding part into a comb-tooth shape, the resonance frequency of the sound generating device shifts to a lower frequency range. However, the surface shapes shown in FIGS. 25A and 25B are merely examples, and the method of making the surface area of the holding part smaller than the surface area of the vibrating body in the contact region between the vibrating body and the holding part is not limited to this.

[0056] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalent scope thereof.

Description of Reference Numerals

[0057] 10…Sound generating device, 11…Vibrator, 12…Holding part, 121, 122…Holding members, 13…Fixing part, 131, 132…Fixing members, 133…Hexagon head bolt, 134…Nut, 135…Hole, 14…Load weight, 141…Resin screw, 142…Resin nut, 143…Metal nut, 20…Sound generating device, 21…Vibrator, 22…Holding part, 221, 222…Holding members, 223…Threaded hole, 23…Support part, 231…Metal screw, 24…Fixing part, 241, 242…Fixing members, 243…Metal screw, 244, 245…Threaded holes, 25…Installation part, 251…Base member, 252, 253…Frame members, 254, 255…Holes, 26…Resonance chamber, 261, 262…Housings, 263…Plate, 264…Opening, 265…Sound radiation port, 50…Piezoelectric vibrator, 51…Piezoelectric element, 52…Metal plate.

Claims

1. A vibrating body having a main surface, a holding portion for holding the vibrating body, a fixing portion for fixing the holding portion, and comprising: the holding portion includes an annular first holding member and an annular second holding member, the first holding member and the second holding member sandwich the periphery of the main surface of the vibrating body, the fixing portion includes an annular first fixing member having a plurality of holes, an annular second fixing member having a plurality of holes, a plurality of screws, and a plurality of nuts, the first fixing member and the second fixing member sandwich both end faces of the holding portion, the screws are arranged along an axial direction perpendicular to the main surface of the vibrating body, are inserted through the holes of the first fixing member and the holes of the second fixing member, and fasten the first fixing member and the second fixing member by screwing the screws and the nuts together, the rigidity of the first fixing member and the second fixing member is smaller than the rigidity of the holding portion, a sound generating device.

2. A vibrating body, a holding portion for holding the vibrating body, a supporting portion for supporting the holding portion, a fixing portion for fixing the supporting portion, and comprising: the holding portion includes an annular first holding member and an annular second holding member, the first holding member and the second holding member sandwich the periphery of the vibrating body, the fixing portion is annular, the inner diameter of the fixing portion is larger than the outer diameters of the first holding member and the second holding member, and the fixing portion is disposed outside the first holding member and the second holding member, the supporting portion is connected to the outer periphery of the holding portion, a sound generating device.

3. The supporting portion includes a plurality of screws, the fixing portion includes a plurality of screw holes extending along a radial direction, the plurality of screws are respectively screwed into the plurality of screw holes, the sound generating device according to Claim 2.

4. The supporting portion includes an elastic member, the elastic member is disposed between the holding portion and the fixing portion, the sound generating device according to Claim 2.

5. The vibrating body has a main surface, the fixing portion is an annular first fixing member having an inner diameter larger than the outer diameter of the first holding member and disposed outside the first holding member, and including a plurality of first screw holes extending along a direction perpendicular to the main surface, an annular second fixing member having an inner diameter larger than the outer diameter of the second holding member and disposed outside the second holding member, and including a plurality of first screw holes extending along a direction perpendicular to the main surface, ​ A plurality of first screws that fasten the first fixing member and the second fixing member through the plurality of first screw holes of the first fixing member and the plurality of first screw holes of the second fixing member; comprising The sound generating device according to claim 2.

6. The support portion includes a plurality of second screws and a plurality of third screws, The first fixing member includes a plurality of second screw holes extending along the radial direction, The second fixing member includes a plurality of second screw holes extending along the radial direction, The plurality of second screws are screwed into the plurality of second screw holes of the first fixing member, The plurality of third screws are screwed into the plurality of second screw holes of the second fixing member, The sound generating device according to claim 5.

7. The holding portion is a single member in which the first holding member and the second holding member are integrally formed. The sound generating device according to claim 2.

8. The sound generating device according to any one of claims 2 to 7, wherein the rigidity of the support portion is smaller than the rigidity of the holding portion.

9. The sound generating device according to any one of claims 1 to 8, further comprising an installation portion for installing the sound generating device on a structure, and the installation portion is attached to the fixing portion.

10. The sound generating device according to claim 9, wherein the rigidity of the installation portion is smaller than the rigidity of the fixing portion.

11. The sound generating device according to any one of claims 1 to 10, further comprising a resonance chamber having a resonance frequency substantially equal to the natural frequency of the vibrating body.

12. The sound generating device according to any one of claims 1 to 11, wherein the vibrating body is a piezoelectric vibrator.

13. The sound generating device according to any one of claims 1 to 12, wherein the holding portion holds the periphery of the vibrating body in surface contact.

14. The sound generating device according to any one of claims 1 to 13, further comprising a load weight attached to the vibrating body.

15. The vibrating body includes a metal plate and a piezoelectric element, The sound generating device according to any one of claims 1 to 14, wherein the holding portion is made of a material having a rigidity smaller than the rigidity of the material of the metal plate.

16. The sound generating device according to any one of claims 1 to 15, wherein the surface roughness of the region of the surface of the holding portion that contacts the vibrating body is rougher than the surface roughness of the region of the surface of the vibrating body that contacts the holding portion.

17. The sound generating device according to any one of claims 1 to 16, wherein the surface area of the region of the surface of the holding portion that contacts the vibrating body is smaller than the surface area of the region of the surface of the vibrating body that contacts the holding portion.

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