Ultrasonic generator

Abstract

To provide an ultrasonic generator with which a hypersonic effect can be achieved easily.SOLUTION: An ultrasonic speaker 40 in an ultrasonic generator includes a first vibration part 71 having a first resonant frequency f1 and a second vibration part 72 having a second resonant frequency f2. When signals including the first resonant frequency and the second resonant frequency are input into the first vibration part 71 and the second vibration part 72, the first vibration part 71 vibrates with sound pressure at the first resonant frequency as a peak value to generate an ultrasonic, and irradiates a human with the generated ultrasonic, and the second vibration part 72 vibrates with sound pressure at the second resonant frequency as a peak value to generate an ultrasonic, and irradiates the human with the generated ultrasonic. The first vibration part 71 and the second vibration part 72 vibrate to generate a difference sound wave at a difference sound frequency fd=|f1-f2|. The difference sound frequency is an audible sound frequency, and a value related to an average value of the sound pressure at the first resonant frequency and the sound pressure at the second resonant frequency is 115 dB SPL or less.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an ultrasonic generator.

Background Art

[0002] Conventionally, as described in Patent Document 1, a multi-resonance ultrasonic transducer including a first resonant unit actuator having a first resonance frequency and a second resonant unit actuator having a second resonance frequency is known. In this multi-resonance ultrasonic transducer, two ultrasonic waves are generated, and a difference ultrasonic wave whose frequency is the difference between the first resonance frequency and the second resonance frequency is generated by the parametric effect.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, when a human is irradiated with ultrasonic waves together with audible sound, a hyper-sonic effect of enhancing the brain function of the human can be obtained. When the multi-resonance ultrasonic transducer described in Patent Document 1 is used for ultrasonic irradiation to obtain the hyper-sonic effect, if the frequency of the difference ultrasonic wave is the frequency of the audible sound, in addition to the irradiated audible sound, the sound due to the difference ultrasonic wave can be heard by the human. At this time, the sound due to the difference ultrasonic wave becomes noise for the human. Therefore, since the human becomes uncomfortable, it is difficult to obtain the hyper-sonic effect.

[0005] An object of the present disclosure is to provide an ultrasonic generator that makes it easier to obtain the hyper-sonic effect.

Means for Solving the Problems

[0006] The invention described in claim 1 is an ultrasonic generator comprising: an audible sound irradiation unit (30) for irradiating a person with audible sound; an ultrasonic irradiation unit (40, 401) including a first vibrating unit (71) having a first resonant frequency (f1) and a second vibrating unit (72) having a second resonant frequency (f2); and a signal unit (38) for outputting a signal including the first resonant frequency and the second resonant frequency to the first vibrating unit and the second vibrating unit, wherein when a signal including the first resonant frequency and the second resonant frequency is input to the first vibrating unit and the second vibrating unit, the first vibrating unit The first vibrating part generates ultrasound by vibrating with the sound pressure of the resonant frequency as its peak value, and the generated ultrasound is irradiated onto a person. The second vibrating part generates ultrasound by vibrating with the sound pressure of the second resonant frequency as its peak value, and the generated ultrasound is irradiated onto a person. The vibrations of the first and second vibrating parts generate difference sound waves with difference tonal frequencies (fd, fd1), which are expressed as the absolute difference between the first resonant frequency and the second resonant frequency. The difference tonal frequency is considered to be the frequency of an audible sound, and the average values ​​of the sound pressure of the first resonant frequency and the sound pressure of the second resonant frequency are used. but This is an ultrasonic generator rated at 115 dBSPL or less.

[0007] As a result, the sound pressure of the difference wave falls below the optimal listening level, which is audible to humans but not unpleasant. Therefore, the difference wave's sound is less likely to be perceived as noise by humans, thus reducing discomfort. Consequently, the hypersonic effect becomes easier to achieve.

[0008] The reference numerals in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described later. [Brief explanation of the drawing]

[0009] [Figure 1] Configuration diagram of the ultrasonic generator according to the first embodiment. [Figure 2] Top view of the ultrasonic speaker for an ultrasonic generator. [Figure 3] Cross-sectional view along line III-III in Figure 2. [Figure 4]A diagram illustrating the relationship between frequency and sound pressure in an ultrasonic generator. [Figure 5] A diagram showing the relationship between the average values ​​of the first and second peak values ​​and the sound pressure of the difference wave. [Figure 6] Configuration diagram of the ultrasonic generator according to the second embodiment. [Figure 7] Top view of the first and second ultrasonic speakers of the ultrasonic generator. [Figure 8] Figure 7 shows a cross-sectional view along line VIII-VIII. [Figure 9] A diagram illustrating the relationship between frequency and sound pressure in an ultrasonic generator. [Figure 10] A top view of the first ultrasonic speaker and the second ultrasonic speaker of the ultrasonic generator according to the third embodiment. [Figure 11] A diagram illustrating the relationship between frequency and sound pressure in an ultrasonic generator. [Modes for carrying out the invention]

[0010] The embodiments will be described below with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be denoted by the same reference numeral, and their descriptions will be omitted.

[0011] (First Embodiment) The ultrasonic generator of this embodiment facilitates the acquisition of the hypersonic effect by irradiating a person with audible sound and ultrasound. Specifically, as shown in Figure 1, the ultrasonic generator 20 includes an audible recording medium 22, an audible signal generator 24, an audible playback circuit 26, an audible amplification circuit 28, and an audible speaker 30. The ultrasonic generator 20 also includes an ultrasonic recording medium 32, an ultrasonic signal generator 34, an ultrasonic playback circuit 36, an ultrasonic amplification circuit 38, and an ultrasonic speaker 40.

[0012] The audible recording medium 22 is, for example, ROM or flash memory, and stores digital information related to audible sound. The audible signal generator 24 is, for example, an optical drive or card reader, and reads the digital information related to audible sound stored in the audible recording medium 22. The audible playback circuit 26 is a DAC, and converts the digital information of audible sound read by the audible signal generator 24 into analog information. The audible amplification circuit 28 is an amplifier, and amplifies the signal corresponding to the analog information related to audible sound converted by the audible playback circuit 26. DAC stands for Digital-to-Analog Converter. Audible sound is defined as sound with a frequency between 20 Hz and 20 kHz.

[0013] The audible speaker 30 corresponds to the audible sound irradiation unit and generates audible sound amplified by the audible amplification circuit 28. In this way, the audible speaker 30 irradiates the human auditory system with audible sound.

[0014] The ultrasonic recording medium 32 is, for example, a ROM or flash memory, and stores digital information related to ultrasound. The ultrasonic signal generator 34 is, for example, an optical drive or card reader, and reads the digital information related to ultrasound stored in the ultrasonic recording medium 32. The ultrasonic playback circuit 36 ​​is a DAC, and converts the digital information related to ultrasound read by the ultrasonic signal generator 34 into analog information. The ultrasonic amplification circuit 38 corresponds to the signal section, and is an amplifier that amplifies the signal corresponding to the analog information related to ultrasound converted by the ultrasonic playback circuit 36. Note that ultrasound is a sound with a frequency higher than 20 kHz.

[0015] The ultrasonic speaker 40 corresponds to the ultrasonic irradiation unit and, for example, by being equipped with a PMUT, generates ultrasonic waves amplified by the ultrasonic amplification circuit 38. This allows the ultrasonic speaker 40 to irradiate humans with ultrasonic waves. PMUT stands for Piezoelectric Micro-machined Ultrasonic Transducer.

[0016] Specifically, as shown in FIGS. 2 and 3, the ultrasonic speaker 40 includes a case 42, a joining member 44, a semiconductor substrate 46, an insulating film 48, a semiconductor film 50, a first piezoelectric film 51, a first electrode 61, a second piezoelectric film 52, a second electrode 62, a first vibrating portion 71, and a second vibrating portion 72.

[0017] The case 42 is formed in a box shape using resin, ceramics, or the like. Further, the case 42 houses the joining member 44, semiconductor substrate 46, insulating film 48, semiconductor film 50, first piezoelectric film 51, first electrode 61, second piezoelectric film 52, second electrode 62, first vibrating portion 71, and second vibrating portion 72, which will be described later. Furthermore, a housing (not shown) that houses the case 42 is attached to, for example, a desk or wall (not shown).

[0018] The joining member 44 is, for example, a silicon-based adhesive or the like. Further, a plurality of joining members 44 are arranged at a predetermined interval on the bottom of the case 42 in a direction D1 orthogonal to the thickness direction DT of the semiconductor substrate 46, which will be described later. Furthermore, a plurality of joining members 44 are arranged at a predetermined interval on the bottom of the case 42 in a direction orthogonal to the direction D1 and the thickness direction DT.

[0019] The semiconductor substrate 46 is formed of, for example, silicon or the like in a square shape. Further, the length of the semiconductor substrate 46 in a direction orthogonal to the thickness direction DT is, for example, 5.0 to 15.0 mm. Furthermore, the semiconductor substrate 46 has a substrate front surface 465, a substrate back surface 467, a first space 471, a second space 472, and a support portion 475.

[0020] The substrate front surface 465 is the surface of the semiconductor substrate 46 on the side opposite to the joining member 44. The substrate back surface 467 is the surface of the semiconductor substrate 46 on the side of the joining member 44. Further, the substrate back surface 467 is joined to the joining member 44. Thereby, an air inflow / outflow space 477 partitioned by the substrate back surface 467, the joining member 44, and the bottom of the case 42 is formed. In the air inflow / outflow space 477, air in the case 42 flows in and out.

[0021] The first space 471 is a hole space that penetrates the substrate surface 465 and the substrate back surface 467. The first space 471 is also in communication with the air inlet / outlet space 477. Furthermore, the first space 471 is formed in a cylindrical shape having an axis extending in the thickness direction DT, for example, by etching. The radius of the first space 471 is, for example, 0.1 to 2.0 mm. Furthermore, the length of the first space 471 in the thickness direction DT is, for example, 0.1 to 1.0 mm.

[0022] The second space 472 is positioned at a predetermined distance from the first space 471 in one direction D1, and is a space of holes that penetrate the substrate surface 465 and the substrate back surface 467. The second space 472 is also in communication with the air inlet / outlet space 477. Furthermore, the second space 472 is formed in a cylindrical shape having an axis extending in the thickness direction DT, for example, by etching. The radius of the second space 472 is, for example, 0.1 to 2.0 mm. Furthermore, the length of the second space 472 in the thickness direction DT is, for example, 0.1 to 1.0 mm.

[0023] The support portion 475 is the part of the semiconductor substrate 46 adjacent to the first space 471. Furthermore, the support portion 475 is the part of the semiconductor substrate 46 adjacent to the second space 472. In addition, the length of the support portion 475 in the thickness direction DT is, for example, 0.1 to 1.0 mm.

[0024] The insulating film 48 is formed of an oxide film, a nitride film, or the like, and therefore has electrical insulating properties. For example, the insulating film 48 is formed of silicon oxide. The length of the insulating film 48 in the thickness direction DT is, for example, 1.0 to 10.0 μm. Furthermore, since the insulating film 48 is formed on the substrate surface 465, it closes the first space 471 and the second space 472 and is supported by the support portion 475.

[0025] The semiconductor film 50 is conductive, for example, due to the doping of a silicon film with p-type impurities. The semiconductor film 50 is formed on an insulating film 48. Furthermore, the length of the semiconductor film 50 in the thickness direction DT is set to 10.0 to 30.0 μm. The semiconductor film 50 is connected to the ultrasonic amplification circuit 38 via bonding wires, pads, connection terminals, etc. (not shown). Here, the semiconductor film 50 is given as an example of a conductive film formed on the insulating film 48, but it is not limited to this. The conductive film formed on the insulating film 48 may be, for example, a film formed from an electrode material such as a titanium-aluminum alloy.

[0026] The first piezoelectric film 51 is formed from an aluminum nitride-based material such as scandium aluminum nitride, or a piezoelectric material such as lead titanium zirconate or zinc oxide. Furthermore, the first piezoelectric film 51 is formed on the portion of the semiconductor film 50 that overlaps with the first space 471 in the thickness direction DT by sputtering or the like. In addition, the first piezoelectric film 51 is formed in a cylindrical shape, for example, having an axis extending in the thickness direction DT. The length of the first piezoelectric film 51 in the thickness direction DT is, for example, 0.5 to 2.0 μm. Furthermore, the axis of the first piezoelectric film 51 coincides with the axis of the first space 471. Here, "coincidence" includes the manufacturing tolerance range.

[0027] The first electrode 61 is made of an electrode material such as a titanium-aluminum alloy and is therefore conductive. The first electrode 61 is formed on the first piezoelectric film 51 by sputtering or vapor deposition. Furthermore, the length of the first electrode 61 in the thickness direction DT is, for example, 100 to 500 nm. The first electrode 61 is connected to the ultrasonic amplification circuit 38 via bonding wires, pads, connection terminals, etc. (not shown).

[0028] The second piezoelectric film 52, like the first piezoelectric film 51, is formed from an aluminum nitride-based material such as scandium aluminum nitride, or a piezoelectric material such as lead titanium zirconate or zinc oxide. Furthermore, the second piezoelectric film 52 is formed by sputtering or the like on the portion of the semiconductor film 50 that overlaps with the second space 472 in the thickness direction DT. The second piezoelectric film 52 is also formed in a cylindrical shape with an axis extending in the thickness direction DT. The length of the second piezoelectric film 52 in the thickness direction DT is, for example, 0.5 to 2.0 μm. Moreover, the axis of the second piezoelectric film 52 coincides with the axis of the second space 472.

[0029] The second electrode 62, like the first electrode 61, is formed from an electrode material such as a titanium-aluminum alloy. The second electrode 62 is formed on the second piezoelectric film 52 by sputtering or vapor deposition. Furthermore, the length of the second electrode 62 in the thickness direction DT is, for example, 100 to 500 nm. The second electrode 62 is connected to the ultrasonic amplification circuit 38 via bonding wires, pads, connection terminals, etc. (not shown).

[0030] The first vibrating section 71 is composed of a first space 471, a portion of the insulating film 48 that overlaps with the first space 471 in the thickness direction DT, a portion of the semiconductor film 50 that overlaps with the first space 471 in the thickness direction DT, the first piezoelectric film 51, and the first electrode 61. When a signal from the ultrasonic amplification circuit 38 is input to the first piezoelectric film 51 via the semiconductor film 50 or the first electrode 61, the first piezoelectric film 51 vibrates in the thickness direction DT. As a result, the portion of the semiconductor film 50 connected to the first piezoelectric film 51 that overlaps with the first space 471 in the thickness direction DT vibrates. In addition, the portion of the insulating film 48 connected to the semiconductor film 50 that overlaps with the first space 471 in the thickness direction DT vibrates. Furthermore, due to the first space 471, the portion of the semiconductor film 50 that overlaps with the first space 471 in the thickness direction DT and the portion of the insulating film 48 that overlaps with the first space 471 in the thickness direction DT vibrates in the thickness direction DT. This generates ultrasound, which is then directed at a person.

[0031] Furthermore, the first vibrating section 71 has a first central axis O1 and a first resonant frequency f1. The first central axis O1 passes through the center of the first vibrating section 71 and extends in the thickness direction DT. Moreover, the first central axis O1 coincides with the axis of the first space 471 and the axis of the first piezoelectric film 51.

[0032] The size of the first space 471, the material and thickness of the insulating film 48, the material and thickness of the semiconductor film 50, the material and size of the first piezoelectric film 51, and the material and size of the first electrode 61 are adjusted so that the first resonant frequency f1 is higher than the ultrasonic frequency of 20 kHz. For example, in this case, the above size, material and thickness are adjusted so that the first resonant frequency f1 is between 40 kHz and 140 kHz.

[0033] The second vibrating section 72 is composed of a second space 472, a portion of the insulating film 48 that overlaps with the second space 472 in the thickness direction DT, a portion of the semiconductor film 50 that overlaps with the second space 472 in the thickness direction DT, the second piezoelectric film 52, and the second electrode 62. Furthermore, since the second space 472 is arranged with a predetermined distance from the first space 471 in one direction D1, the second vibrating section 72 is aligned with the first vibrating section 71 with a predetermined distance from it in one direction D1. When a signal from the ultrasonic amplification circuit 38 is input to the second piezoelectric film 52 via the semiconductor film 50 or the second electrode 62, the second piezoelectric film 52 vibrates in the thickness direction DT. As a result, the portion of the semiconductor film 50 connected to the second piezoelectric film 52 that overlaps with the second space 472 in the thickness direction DT vibrates. Also, the portion of the insulating film 48 connected to the semiconductor film 50 that overlaps with the second space 472 in the thickness direction DT vibrates. Furthermore, the second space 472 causes the portion of the semiconductor film 50 that overlaps with the second space 472 in the thickness direction DT, and the portion of the insulating film 48 that overlaps with the second space 472 in the thickness direction DT, to vibrate in the thickness direction DT. This generates ultrasound, which is then irradiated onto a person.

[0034] Furthermore, the second vibrating section 72 has a second central axis O2 and a second resonant frequency f2. The second central axis O2 passes through the center of the second vibrating section 72 and extends in the thickness direction DT. Moreover, the second central axis O2 coincides with the axis of the second space 472 and the axis of the second piezoelectric film 52.

[0035] The size of the second space 472, the material and thickness of the insulating film 48, the material and thickness of the semiconductor film 50, the material and size of the second piezoelectric film 52, and the material and size of the second electrode 62 are adjusted so that the second resonant frequency f2 is higher than the ultrasonic frequency of 20 kHz. For example, in this case, the above size, material and thickness are adjusted so that the second resonant frequency f2 is between 40 kHz and 140 kHz.

[0036] Here, the digital information related to ultrasound stored in the ultrasonic recording medium 32 includes information such as a sine wave or cosine wave having a first resonant frequency f1 and a second resonant frequency f2. Therefore, signals such as a sine wave or cosine wave having a first resonant frequency f1 and a second resonant frequency f2 are input from the ultrasonic amplification circuit 38 to the first piezoelectric film 51 and the second piezoelectric film 52. As a result, as shown in Figure 4, the first vibrating part 71 vibrates with a peak sound pressure value of the first resonant frequency f1, and the second vibrating part 72 vibrates with a peak sound pressure value of the second resonant frequency f2. Therefore, ultrasound with a relatively high sound pressure is generated. Consequently, ultrasound is more likely to irradiate humans. Also, at this time, a difference sound wave with a difference frequency fd is generated due to the parametric effect. Furthermore, the difference frequency fd is expressed as the absolute value |f1-f2| of the difference between the first resonant frequency f1 and the second resonant frequency f2. Furthermore, the first resonant frequency f1 and the second resonant frequency f2 are adjusted so that the difference tone frequency fd is between 20 Hz and 20 kHz, which are the frequencies of audible sound. In addition, the difference between the first resonant frequency f1 and the second resonant frequency f2 is adjusted to be relatively small. As a result, the sound pressure of the ultrasound generated by the first vibrating part 71 and the second vibrating part 72 becomes more uniform. Therefore, the reproducibility of the sound source is improved, and the hypersonic effect is more easily obtained.

[0037] Furthermore, the sound pressure at the first resonant frequency f1 is defined as the first peak value Pv1. The sound pressure at the second resonant frequency f2 is defined as the second peak value Pv2. The average value of the first peak value Pv1 and the second peak value Pv2, i.e., (Pv1 + Pv2) / 2, is set to be 115 dBSPL or less. To achieve this, the sizes of the first and second spaces 471 and 472, the material and thickness of the insulating film 48, the material and thickness of the semiconductor film 50, the material and size of the first piezoelectric film 51 and the second piezoelectric film 52, and the material and size of the first and second electrodes 61 and 62 are adjusted. Additionally, the amplitude of the signal from the ultrasonic amplification circuit 38 is adjusted. Note that in Figure 4, the first peak value Pv1 and the second peak value Pv2 are set to the same value, but they may be different.

[0038] Furthermore, returning to Figures 2 and 3, the distance from the first central axis O1 to the second central axis O2 in one direction D1 is defined as the distance Lp between the vibrating parts. The distance Lp between the vibrating parts is set to be less than or equal to the wavelength of the difference sound wave produced by the first vibrating part 71 and the second vibrating part 72, as shown in the following relation (1). For example, if the difference sound frequency fd is 20 kHz, the speed of sound is approximately 340 m / s, and therefore the wavelength of the difference sound wave is 17 mm. Thus, in this case, the distance Lp between the vibrating parts is set to 17 mm or less. In the following relation (1), λd is the wavelength of the difference sound wave, and c is the speed of sound.

[0039] Lp≦λd λd = c / fd ... (1)

[0040] As described above, the ultrasonic generator 20 of the first embodiment is configured as follows. In this ultrasonic generator 20, for example, when the power of the ultrasonic generator 20 is turned on, audible sound from the audible speaker 30 is irradiated onto the human auditory system, and ultrasonic waves from the ultrasonic speaker 40 are irradiated onto the human body. As a result, a hypersonic effect is obtained for humans. Next, it will be explained that the ultrasonic generator 20 of this embodiment makes it easy to obtain a hypersonic effect.

[0041] Here, if the difference tone frequency fd is the frequency of an audible sound, then in addition to the audible sound emitted from the audible speaker 30, the sound produced by the difference sound wave is also audible to humans. In this case, the sound produced by the difference sound wave becomes noise to humans. Therefore, because it is unpleasant to humans, the hypersonic effect is difficult to obtain.

[0042] Therefore, in the ultrasonic generator 20 of this embodiment, the average value of the first peak value Pv1 and the second peak value Pv2, i.e., (Pv1 + Pv2) / 2, is set to 115 dBSPL or less.

[0043] As a result, as shown in Figure 5, the sound pressure of the difference wave is at the optimal listening level, which is a sound pressure level that is audible to humans but not unpleasant, i.e., 60 dBSPL or less. Therefore, the sound from the difference wave is suppressed from becoming noise to humans, thus reducing discomfort to humans. Consequently, the hypersonic effect is more easily obtained. The relationship between the average values ​​of the first peak value Pv1 and the second peak value Pv2 shown in Figure 5 and the sound pressure of the difference wave is plotted when the first resonant frequency f1 is 58.8 kHz, the second resonant frequency f2 is 67.6 kHz, and the difference sound frequency fd is 8.8 kHz. The sound pressure of the difference wave is measured by collecting the sound generated by the first vibrating part 71 and the second vibrating part 72 on the surface of the first electrode 61 or the surface of the second electrode 62 using a microphone (not shown), and then performing frequency analysis on the collected sound. Furthermore, the first peak value Pv1 and the second peak value Pv2 are also measured by collecting the sound generated by the first vibrating section 71 and the second vibrating section 72 on the surface of the first electrode 61 or the second electrode 62 using a microphone (not shown), and then performing frequency analysis on the collected sound. From these measured first peak value Pv1 and second peak value Pv2, the average value of the first peak value Pv1 and the second peak value Pv2, i.e., (Pv1 + Pv2) / 2, is calculated. Furthermore, the position of the microphone (not shown) for measuring the sound pressure of the difference wave, the first peak value Pv1, and the second peak value Pv2 is, but not limited to, the surface of the first electrode 61 or the surface of the second electrode 62. For example, the position of the microphone (not shown) for measuring the sound pressure of the difference wave, the first peak value Pv1, and the second peak value Pv2 may be the surface of case 42 on the side of the ultrasonic irradiation direction.

[0044] Furthermore, it is more preferable that the average value of the first peak value Pv1 and the second peak value Pv2, i.e., (Pv1 + Pv2) / 2, be 105 dBSPL or less.

[0045] As a result, the sound pressure of the difference wave is reduced to the minimum acceptable level, i.e., 43 dBSPL or less, which is a sound pressure level that is difficult for humans to hear and does not cause discomfort. Therefore, the sound produced by the difference wave becomes difficult for humans to hear, thus suppressing discomfort. Consequently, the hypersonic effect is more easily achieved.

[0046] Furthermore, the ultrasonic generator 20 of the first embodiment also provides the following effects.

[0047] [1] The distance Lp between the vibrating parts is defined as the value obtained by dividing the speed of sound by the difference tone frequency fd, i.e., less than or equal to λd. Note that the distance Lp between the vibrating parts corresponds to the distance from the center of the first vibrating part 71 to the center of the second vibrating part 72.

[0048] This allows the first vibrating part 71 and the second vibrating part 72 to be brought closer together compared to the case where the distance Lp between the vibrating parts is greater than the value obtained by dividing the speed of sound by the difference tone frequency fd. Therefore, the size of the ultrasonic generator 20 can be reduced. Consequently, an increase in the size of the ultrasonic generator 20 is suppressed.

[0049] (Second Embodiment) As shown in Figure 6, the ultrasonic generator 20 of the second embodiment includes a first ultrasonic speaker 401 and a second ultrasonic speaker 402 instead of the ultrasonic speaker 40. This is a difference from the first embodiment.

[0050] The first ultrasonic speaker 401 corresponds to the ultrasonic speaker 40 and is equivalent to the first ultrasonic irradiation unit. Furthermore, as shown in Figures 7 and 8, the first ultrasonic speaker 401 includes a first case 421, a first bonding member 441, and a first semiconductor substrate 461 instead of the case 42, bonding member 44, and semiconductor substrate 46. In addition, the first ultrasonic speaker 401 includes a first insulating film 481 and a first semiconductor film 501 instead of the insulating film 48 and semiconductor film 50. The first ultrasonic speaker 401 also includes a first vibrating unit 71 and a second vibrating unit 72.

[0051] The first case 421 corresponds to case 42. The first bonding member 441 corresponds to bonding member 44. The first semiconductor substrate 461 corresponds to the first substrate and also to semiconductor substrate 46. The first semiconductor substrate 461 also has a first substrate surface 4651, a first substrate back surface 4671, a first space 471, a second space 472, and a first support portion 4751. The first substrate surface 4651 corresponds to substrate surface 465. The first substrate back surface 4671 corresponds to substrate back surface 467. The first support portion 4751 corresponds to support portion 475. A first air inflow / outflow space 4771 is formed, partitioned by the first substrate back surface 4671, the first bonding member 441, and the first case 421. Air flows in and out of the first air inflow / outflow space 4771 from inside the first case 421. Therefore, the first air inflow / outflow space 4771 corresponds to air inflow / outflow space 477. The first insulating film 481 corresponds to the insulating film 48. The first semiconductor film 501 corresponds to the semiconductor film 50. Therefore, the explanation of the first case 421, the first bonding member 441, the first semiconductor substrate 461, the first insulating film 481, and the first semiconductor film 501 will be omitted.

[0052] The first vibrating section 71 is composed of a first space 471, a portion of the first insulating film 481 that overlaps with the first space 471 in the thickness direction DT, a portion of the first semiconductor film 501 that overlaps with the first space 471 in the thickness direction DT, a first piezoelectric film 51, and a first electrode 61. The second vibrating section 72 is composed of a second space 472, a portion of the first insulating film 481 that overlaps with the second space 472 in the thickness direction DT, a portion of the first semiconductor film 501 that overlaps with the second space 472 in the thickness direction DT, a second piezoelectric film 52, and a second electrode 62. Furthermore, the first vibrating section 71 and the second vibrating section 72 generate a first difference sound wave with a first difference frequency fd1. The first difference frequency fd1 corresponds to the difference frequency fd. The first difference sound wave corresponds to the difference sound wave generated by the first vibrating section 71 and the second vibrating section 72.

[0053] The second ultrasonic speaker 402 corresponds to the second ultrasonic irradiation unit. The second ultrasonic speaker 402 also includes a second case 422, a second bonding member 442, a second semiconductor substrate 462, a second insulating film 482, a second semiconductor film 502, a third piezoelectric film 53, a third electrode 63, a fourth piezoelectric film 54, a fourth electrode 64, a third vibrating unit 73, and a fourth vibrating unit 74.

[0054] The second case 422 is formed in a box shape from resin, ceramics, or the like. The second case 422 also houses the second bonding member 442, the second semiconductor substrate 462, the second insulating film 482, the second semiconductor film 502, the third piezoelectric film 53, the third electrode 63, the fourth piezoelectric film 54, the fourth electrode 64, the third vibrating part 73, and the fourth vibrating part 74, which will be described later. Furthermore, the housing that houses the second case 422 is mounted, for example, on a desk or wall, which will not be shown. The second case 422 is also aligned with the first case 421 in one direction D1.

[0055] The second joining member 442 is, for example, a silicone-based adhesive. Multiple second joining members 442 are arranged at predetermined intervals in one direction D1 at the bottom of the second case 422. Furthermore, multiple second joining members 442 are arranged at predetermined intervals in directions perpendicular to both the one direction D1 and the thickness direction DT at the bottom of the second case 422.

[0056] The second semiconductor substrate 462 corresponds to the second substrate and is formed, for example, in a rectangular shape from silicon or the like. The length of the second semiconductor substrate 462 in the direction perpendicular to the thickness direction DT is, for example, 5.0 to 15.0 mm. Furthermore, since the second case 422 is aligned with the first case 421 in one direction D1, the second semiconductor substrate 462 is aligned with the first semiconductor substrate 461 in one direction D1. The second semiconductor substrate 462 also has a second substrate surface 4652, a second substrate back surface 4672, a third space 473, a fourth space 474, and a second support portion 4752.

[0057] The second substrate surface 4652 is the side of the second semiconductor substrate 462 opposite to the second bonding member 442. The second substrate back surface 4672 is the side of the second semiconductor substrate 462 facing the second bonding member 442. The second substrate back surface 4672 is also bonded to the second bonding member 442. This forms a second air inflow / outflow space 4772, which is partitioned by the second substrate back surface 4672, the second bonding member 442, and the bottom of the second case 422. Air flows in and out of the second air inflow / outflow space 4772 within the second case 422.

[0058] The third space 473 is a hole space that penetrates the surface 4652 and the back surface 4672 of the second substrate. The third space 473 is also in communication with the second air inlet / outlet space 4772. Furthermore, the third space 473 is formed in a cylindrical shape having an axis extending in the thickness direction DT, for example by etching. The radius of the third space 473 is, for example, 0.1 to 2.0 mm. Furthermore, the length of the third space 473 in the thickness direction DT is, for example, 0.1 to 1.0 mm.

[0059] The fourth space 474 is positioned at a predetermined distance from the third space 473 in one direction D1, and is a space of a hole that penetrates the surface 4652 and the back surface 4672 of the second substrate. The fourth space 474 is also in communication with the second air inlet / outlet space 4772. Furthermore, the fourth space 474 is formed in a cylindrical shape having an axis extending in the thickness direction DT, for example, by etching. The radius of the fourth space 474 is, for example, 0.1 to 2.0 mm. Furthermore, the length of the fourth space 474 in the thickness direction DT is, for example, 0.1 to 1.0 mm.

[0060] The second support portion 4752 is the portion of the second semiconductor substrate 462 adjacent to the third space 473. Furthermore, the second support portion 4752 is the portion of the second semiconductor substrate 462 adjacent to the fourth space 474. In addition, the length of the second support portion 4752 in the thickness direction DT is, for example, 0.1 to 1.0 mm.

[0061] The second insulating film 482 is formed of an oxide film, a nitride film, or the like, and therefore has electrical insulating properties. For example, the second insulating film 482 is formed of silicon oxide. The length of the second insulating film 482 in the thickness direction DT is, for example, 1.0 to 10.0 μm. Furthermore, since the second insulating film 482 is formed on the second substrate surface 4652, it closes the third space 473 and the fourth space 474 and is supported by the second support portion 4752.

[0062] The second semiconductor film 502 is conductive, for example, by doping a silicon film with p-type impurities. The second semiconductor film 502 is formed on the second insulating film 482. Furthermore, the length of the second semiconductor film 502 in the thickness direction DT is set to 10.0 to 30.0 μm. The second semiconductor film 502 is connected to the ultrasonic amplification circuit 38 via bonding wires, pads, connection terminals, etc. (not shown). Here, the second semiconductor film 502 is given as a conductive film formed on the second insulating film 482, but it is not limited to this. The conductive film formed on the second insulating film 482 may be, for example, a film formed from an electrode material such as a titanium-aluminum alloy.

[0063] The third piezoelectric film 53 is formed from an aluminum nitride-based material such as scandium aluminum nitride, or a piezoelectric material such as lead titanium zirconate or zinc oxide. Furthermore, the third piezoelectric film 53 is formed by sputtering or the like on the portion of the second semiconductor film 502 that overlaps with the third space 473 in the thickness direction DT. Additionally, the third piezoelectric film 53 is formed in a cylindrical shape, for example, having an axis extending in the thickness direction DT. The length of the third piezoelectric film 53 in the thickness direction DT is, for example, 0.5 to 2.0 μm. Moreover, the axis of the third piezoelectric film 53 coincides with the axis of the third space 473.

[0064] The third electrode 63 is made of an electrode material such as a titanium-aluminum alloy and is therefore conductive. The length of the third electrode 63 in the thickness direction DT is, for example, 100 to 500 nm. Furthermore, the third electrode 63 is formed on the third piezoelectric film 53 by sputtering or vapor deposition. The third electrode 63 is connected to the ultrasonic amplification circuit 38 via bonding wires, pads, connection terminals, etc. (not shown).

[0065] The fourth piezoelectric film 54, like the third piezoelectric film 53, is formed from an aluminum nitride-based material such as scandium aluminum nitride, or a piezoelectric material such as lead titanium zirconate or zinc oxide. Furthermore, the fourth piezoelectric film 54 is formed by sputtering or the like on the portion of the second semiconductor film 502 that overlaps with the fourth space 474 in the thickness direction DT. The fourth piezoelectric film 54 is also formed in a cylindrical shape with an axis extending in the thickness direction DT. The length of the fourth piezoelectric film 54 in the thickness direction DT is, for example, 0.5 to 2.0 μm. Additionally, the axis of the fourth piezoelectric film 54 coincides with the axis of the fourth space 474.

[0066] The fourth electrode 64, like the third electrode 63, is formed from an electrode material such as a titanium-aluminum alloy. Furthermore, the fourth electrode 64 is formed on the fourth piezoelectric film 54 by sputtering or vapor deposition. The length of the fourth electrode 64 in the thickness direction DT is, for example, 100 to 500 nm. The fourth electrode 64 is connected to the ultrasonic amplification circuit 38 via bonding wires, pads, connection terminals, etc. (not shown).

[0067] The third vibrating section 73 is composed of a third space 473, a portion of the second insulating film 482 that overlaps with the third space 473 in the thickness direction DT, a portion of the second semiconductor film 502 that overlaps with the third space 473 in the thickness direction DT, a third piezoelectric film 53, and a third electrode 63. When a signal from the ultrasonic amplification circuit 38 is input to the third piezoelectric film 53 via the second semiconductor film 502 or the third electrode 63, the third piezoelectric film 53 vibrates in the thickness direction DT. As a result, the portion of the second semiconductor film 502 connected to the third piezoelectric film 53 that overlaps with the third space 473 in the thickness direction DT vibrates. In addition, the portion of the second insulating film 482 connected to the second semiconductor film 502 that overlaps with the third space 473 in the thickness direction DT vibrates. Furthermore, the third space 473 causes the portion of the second semiconductor film 502 that overlaps with the third space 473 in the thickness direction DT, and the portion of the second insulating film 482 that overlaps with the third space 473 in the thickness direction DT, to vibrate in the thickness direction DT. This generates ultrasound, which is then irradiated onto a person.

[0068] Furthermore, the third vibrating section 73 has a third central axis O3 and a third resonant frequency f3. The third central axis O3 passes through the center of the third vibrating section 73 and extends in the thickness direction DT. Moreover, the third central axis O3 coincides with the axis of the third space 473 and the axis of the third piezoelectric film 53.

[0069] The size of the third space 473, the material and thickness of the second insulating film 482, the material and thickness of the second semiconductor film 502, the material and size of the third piezoelectric film 53, and the material and size of the third electrode 63 are adjusted so that the third resonant frequency f3 is greater than 20 kHz. For example, in this case, the above size, material, and thickness are adjusted so that the third resonant frequency f3 is between 40 kHz and 140 kHz.

[0070] The fourth vibrating section 74 is composed of a fourth space 474, a portion of the second insulating film 482 that overlaps with the fourth space 474 in the thickness direction DT, a portion of the second semiconductor film 502 that overlaps with the fourth space 474 in the thickness direction DT, a fourth piezoelectric film 54, and a fourth electrode 64. Furthermore, since the fourth space 474 is positioned at a predetermined distance from the third space 473, the fourth vibrating section 74 is aligned with the third vibrating section 73 at a predetermined distance in one direction D1. In addition, since the second ultrasonic speaker 402 is aligned with the first ultrasonic speaker 401, the first vibrating section 71, the second vibrating section 72, the third vibrating section 73, and the fourth vibrating section 74 are aligned in one direction D1. When a signal from the ultrasonic amplification circuit 38 is input to the fourth piezoelectric film 54 via the second semiconductor film 502 or the fourth electrode 64, the fourth piezoelectric film 54 vibrates in the thickness direction DT. As a result, the portion of the second semiconductor film 502 connected to the fourth piezoelectric film 54 that overlaps with the fourth space 474 in the thickness direction DT vibrates. Also, the portion of the second insulating film 482 connected to the second semiconductor film 502 that overlaps with the fourth space 474 in the thickness direction DT vibrates. Furthermore, the portion of the second semiconductor film 502 that overlaps with the fourth space 474 in the thickness direction DT and the portion of the second insulating film 482 that overlaps with the fourth space 474 in the thickness direction DT vibrates in the thickness direction DT. This generates ultrasound, which is then irradiated onto a person.

[0071] Furthermore, the fourth vibrating section 74 has a fourth central axis O4 and a fourth resonant frequency f4. The fourth central axis O4 passes through the center of the fourth vibrating section 74 and extends in the thickness direction DT. Moreover, the fourth central axis O4 coincides with the axis of the fourth space 474 and the axis of the fourth piezoelectric film 54.

[0072] The size of the fourth space 474, the material and thickness of the second insulating film 482, the material and thickness of the second semiconductor film 502, the material and size of the fourth piezoelectric film 54, and the material and size of the fourth electrode 64 are adjusted so that the fourth resonant frequency f4 is greater than 20 kHz. For example, in this case, the size, material and thickness are adjusted so that the fourth resonant frequency f4 is between 40 kHz and 140 kHz.

[0073] Here, the digital information related to ultrasound stored in the ultrasonic recording medium 32 includes information such as a sine wave or cosine wave having a third resonant frequency f3 and a fourth resonant frequency f4. Therefore, signals such as a sine wave or cosine wave having a third resonant frequency f3 and a fourth resonant frequency f4 are input from the ultrasonic amplification circuit 38 to the third piezoelectric film 53 and the fourth piezoelectric film 54. As a result, as shown in Figure 9, the third vibrating part 73 vibrates with a peak sound pressure value of the third resonant frequency f3, and the fourth vibrating part 74 vibrates with a peak sound pressure value of the fourth resonant frequency f4. Therefore, ultrasound with a relatively high sound pressure is generated. Consequently, ultrasound is more likely to irradiate humans. Also, at this time, a second difference sound wave with a second difference frequency fd2 is generated due to the parametric effect. Furthermore, the second difference frequency fd2 is expressed as the absolute value |f3-f4| of the difference between the third resonant frequency f3 and the fourth resonant frequency f4. Furthermore, the third and fourth resonant frequencies f3 and f4 are adjusted so that the second difference tone frequency fd2 falls between 20 Hz and 20 kHz, which are audible frequencies. In addition, the difference between the third and fourth resonant frequencies f3 and f4 is adjusted to be relatively small. This makes it easier for the sound pressure of the ultrasound generated by the third and fourth vibrating parts 73 and 74 to become uniform. As a result, the reproducibility of the sound source is improved, making it easier to obtain the hypersonic effect.

[0074] Furthermore, the sound pressure at the third resonant frequency f3 is defined as the third peak value Pv3. The sound pressure at the fourth resonant frequency f4 is defined as the fourth peak value Pv4. The average value of the third peak value Pv3 and the fourth peak value Pv4, i.e., (Pv3 + Pv4) / 2, is set to be 115 dBSPL or less. To achieve this, the sizes of the third space 473 and the fourth space 474, the material and thickness of the second insulating film 482, the material and thickness of the second semiconductor film 502, the material and size of the third piezoelectric film 53 and the fourth piezoelectric film 54, and the material and size of the third electrode 63 and the fourth electrode 64 are adjusted. Additionally, the amplitude of the signal from the ultrasonic amplification circuit 38 is adjusted for this purpose. Note that in Figure 9, the first peak value Pv1, the second peak value Pv2, the third peak value Pv3, and the fourth peak value Pv4 are set to the same value, but they may be different.

[0075] Furthermore, returning to Figures 7 and 8, let Lp1 be the distance between the first vibrating parts, from the first central axis O1 to the second central axis O2 in one direction D1. Let Lp2 be the distance between the second vibrating parts, from the third central axis O3 to the fourth central axis O4 in one direction D1.

[0076] Furthermore, the distance Lp1 between the first vibrating parts is set to be less than or equal to the wavelength of the first difference sound wave. The wavelength of the first difference sound wave is the value obtained by dividing the speed of sound by the first difference sound frequency fd1. Also, the distance Lp2 between the second vibrating parts is set to be less than or equal to the wavelength of the second difference sound wave. The wavelength of the second difference sound wave is the value obtained by dividing the speed of sound by the second difference sound frequency fd2.

[0077] Furthermore, let Ls1 be the distance between the first speaker and the third central axis in one direction D1, from the first central axis O1 to the third central axis O3. Let Ls2 be the distance between the second speaker and the fourth central axis in one direction D1, from the first central axis O1 to the fourth central axis O4. Let Ls3 be the distance between the third speaker and the second central axis O2 to the third central axis O3 in one direction D1. Let Ls4 be the distance between the fourth speaker and the second central axis O2 to the fourth central axis O4 in one direction D1.

[0078] Furthermore, the distance Ls1 between the first speakers is greater than the value obtained by dividing the speed of sound by the absolute value of the difference between the first resonant frequency f1 and the third resonant frequency f3, |f1-f3|, i.e., Ls1>c / |f1-f3|. Similarly, the distance Ls2 between the second speakers is greater than the value obtained by dividing the speed of sound by the absolute value of the difference between the first resonant frequency f1 and the fourth resonant frequency f4, |f1-f4|, i.e., Ls2>c / |f1-f4|. Moreover, the distance Ls3 between the third speakers is greater than the value obtained by dividing the speed of sound by the absolute value of the difference between the second resonant frequency f2 and the third resonant frequency f3, |f2-f3|, i.e., Ls3>c / |f2-f3|. Furthermore, the distance Ls4 between the fourth speaker is greater than the value obtained by dividing the speed of sound by the absolute difference between the second resonant frequency f2 and the fourth resonant frequency f4, |f2-f4|, i.e., Ls4 > c / |f2-f4|.

[0079] As described above, the ultrasonic generator 20 of the second embodiment is configured as described above. The ultrasonic generator 20 of the second embodiment also provides the same effects as the first embodiment. In addition, the second embodiment also provides the effects described below.

[0080] [2] Here, difference sound waves are generated by the first vibrating section 71 and the third vibrating section 73. When the frequency of these generated difference sound waves is the frequency of an audible sound, the sound produced by the difference sound waves is heard by humans in addition to the audible sound emitted from the audible speaker 30. At this time, the sound produced by the difference sound waves becomes noise to humans. For this reason, it is unpleasant to humans, and the hypersonic effect is difficult to obtain.

[0081] Therefore, the distance Ls1 between the first speakers is greater than the value obtained by dividing the speed of sound by the absolute value of the difference between the first resonant frequency f1 and the third resonant frequency f3, |f1-f3|, i.e., Ls1 > c / |f1-f3|. Note that the absolute value of the difference between the first resonant frequency f1 and the third resonant frequency f3, |f1-f3|, corresponds to the first frequency.

[0082] As a result, the first vibrating section 71 and the third vibrating section 73 are separated by more than one wavelength of the difference sound wave produced by the first vibrating section 71 and the third vibrating section 73. Therefore, the phase difference between the ultrasound generated by the first vibrating section 71 and the ultrasound generated by the third vibrating section 73 becomes larger. Consequently, the ultrasound generated by the first vibrating section 71 and the ultrasound generated by the third vibrating section 73 tend to weaken each other. Therefore, the sound pressure of the difference sound wave produced by the first vibrating section 71 and the third vibrating section 73 tends to decrease. Consequently, the sound produced by this difference sound wave is less likely to become noise to humans, thus reducing discomfort to humans. Therefore, the hypersonic effect is more easily obtained.

[0083] Furthermore, the distance Ls2 between the second speaker is greater than the value obtained by dividing the speed of sound by the absolute difference between the first resonant frequency f1 and the fourth resonant frequency f4, |f1-f4|, i.e., Ls2 > c / |f1-f4|. Note that the absolute difference between the first resonant frequency f1 and the fourth resonant frequency f4, |f1-f4|, corresponds to the second frequency.

[0084] As a result, similar to the above, the sound pressure of the difference sound waves produced by the first vibrating section 71 and the fourth vibrating section 74 is easily reduced. Therefore, discomfort to humans caused by these difference sound waves is suppressed. Thus, the hypersonic effect is more easily obtained.

[0085] Furthermore, the distance Ls3 between the third speaker is greater than the value obtained by dividing the speed of sound by the absolute difference between the second resonant frequency f2 and the third resonant frequency f3, |f2-f3|, i.e., Ls3 > c / |f2-f3|. Note that the absolute difference between the second resonant frequency f2 and the third resonant frequency f3, |f2-f3|, corresponds to the third frequency.

[0086] As a result, similar to the above, the sound pressure of the difference sound waves produced by the second vibrating section 72 and the third vibrating section 73 is easily reduced. Therefore, discomfort to humans caused by these difference sound waves is suppressed. Consequently, the hypersonic effect is more easily obtained.

[0087] Furthermore, the distance Ls4 between the fourth speaker is greater than the value obtained by dividing the speed of sound by the absolute difference between the second resonant frequency f2 and the fourth resonant frequency f4, |f2-f4|, i.e., Ls4 > c / |f2-f4|. Note that the absolute difference between the second resonant frequency f2 and the fourth resonant frequency f4, |f2-f4|, corresponds to the fourth frequency.

[0088] As a result, similar to the above, the sound pressure of the difference sound waves produced by the second vibrating section 72 and the fourth vibrating section 74 tends to decrease. Therefore, discomfort to humans caused by these difference sound waves is suppressed. Thus, the hypersonic effect is more easily obtained.

[0089] (Third embodiment) In the ultrasonic generator 20 of the third embodiment, as shown in Figure 10, the first ultrasonic speaker 401 and the second ultrasonic speaker 402 differ from those of the second embodiment. Specifically, the first ultrasonic speaker 401 includes a first vibrating section 71, a second vibrating section 72, a third vibrating section 73, a fourth vibrating section 74, a fifth vibrating section 75, a sixth vibrating section 76, a seventh vibrating section 77, an eighth vibrating section 78, a ninth vibrating section 79, a tenth vibrating section 80, and an eleventh vibrating section 81. The second ultrasonic speaker 402 includes a twelfth vibrating section 82, a thirteenth vibrating section 83, a fourteenth vibrating section 84, a fifteenth vibrating section 85, a sixteenth vibrating section 86, a seventeenth vibrating section 87, an eighteenth vibrating section 88, a nineteenth vibrating section 89, a twenty-tenth vibrating section 90, a twenty-first vibrating section 91, and a twenty-second vibrating section 92. Other than these, it differs from the second embodiment.

[0090] The first to eleventh vibrating sections 71 to 81 are arranged on the first semiconductor substrate 461. The first to eleventh vibrating sections 71 to 81 are aligned in one direction D1, and also in directions perpendicular to both the one direction D1 and the thickness direction DT. For example, in the one direction D1, the first vibrating section 71, the second vibrating section 72, the third vibrating section 73, and the fourth vibrating section 74 are arranged in that order. Furthermore, the fifth vibrating section 75 is adjacent to the first vibrating section 71 in a direction perpendicular to both the one direction D1 and the thickness direction DT. Also, in the one direction D1, the fifth vibrating section 75, the sixth vibrating section 76, and the seventh vibrating section 77 are arranged in that order. Furthermore, the eighth vibrating section 78 is adjacent to the fifth vibrating section 75 in a direction perpendicular to both the one direction D1 and the thickness direction DT. Furthermore, in one direction D1, the eighth vibration section 78, the ninth vibration section 79, the tenth vibration section 80, and the eleventh vibration section 81 are arranged in that order.

[0091] Furthermore, the first to eleventh vibrating sections 71 to 81 each include a corresponding space, a portion of the first insulating film 481, a portion of the first semiconductor film 501, a piezoelectric film, and an electrode. In addition, the first to eleventh vibrating sections 71 to 81 each have first to eleventh central axes O1 to O11 and first to eleventh resonant frequencies f1 to f11.

[0092] The first resonant frequency f1 is, for example, set to 140 kHz. The second resonant frequency f2 is, for example, set to 110 kHz. The third resonant frequency f3 is, for example, set to 100 kHz. The fourth resonant frequency f4 is, for example, set to 70 kHz. The fifth resonant frequency f5 is, for example, set to 40 kHz. The sixth resonant frequency f6 is, for example, set to 50 kHz. The seventh resonant frequency f7 is, for example, set to 60 kHz. The eighth resonant frequency f8 is, for example, set to 130 kHz. The ninth resonant frequency f9 is, for example, set to 120 kHz. The tenth resonant frequency f10 is, for example, set to 90 kHz. The eleventh resonant frequency f11 is, for example, set to 80 kHz. In Figure 10, the values ​​of the first to eleventh resonant frequencies f1 to f11 are shown so that each resonant frequency can be identified.

[0093] Here, the digital information related to ultrasound stored in the ultrasonic recording medium 32 includes information such as sine waves or cosine waves having first to eleventh resonant frequencies f1 to f11. Therefore, signals such as sine waves or cosine waves having first to eleventh resonant frequencies f1 to f11 are input from the ultrasonic amplification circuit 38 to the first to eleventh vibrating units 71 to 81. As a result, as shown in Figure 11, the first to eleventh vibrating units 71 to 81 each vibrate with a peak sound pressure value at the first to eleventh resonant frequencies f1 to f11. Therefore, ultrasound with a relatively high sound pressure is generated. Consequently, ultrasound is more likely to be transmitted to humans.

[0094] Furthermore, the sound pressures at the first to eleventh resonant frequencies f1 to f11 are denoted as the first to eleventh peak values ​​Pv1 to Pv11, respectively. The average value of the first to eleventh peak values ​​Pv1 to Pv11 is set to be 115 dBSPL or less. To achieve this, the size of the space between the first to eleventh vibrating parts 71 to 81, the material and thickness of the first insulating film 481, the material and thickness of the first semiconductor film 501, the material and size of the piezoelectric film, the material and size of the electrodes, etc., are adjusted. Also, the amplitude of the signal from the ultrasonic amplification circuit 38, etc., is adjusted for this purpose. Note that in Figure 11, the first to eleventh peak values ​​Pv1 to Pv11 are set to the same value, but they may be different. In addition, the average value of the peak values ​​in a combination of two vibrating parts among the first to eleventh vibrating parts 71 to 81 where the frequency of the difference sound wave is the frequency of the audible sound may be 115 dBSPL or less.

[0095] The 12th to 22nd vibration sections 82 to 92 are arranged on the second semiconductor substrate 462. Furthermore, the 12th to 22nd vibration sections 82 to 92 are aligned in one direction D1, as well as in directions perpendicular to both the one direction D1 and the thickness direction DT. For example, in the one direction D1, the 12th vibration section 82, the 13th vibration section 83, the 14th vibration section 84, and the 15th vibration section 85 are arranged in that order. Additionally, the 16th vibration section 86 is adjacent to the 12th vibration section 82 in a direction perpendicular to both the one direction D1 and the thickness direction DT. Also, in the one direction D1, the 16th vibration section 86, the 17th vibration section 87, and the 18th vibration section 88 are arranged in that order. Furthermore, the 19th vibration section 89 is adjacent to the 16th vibration section 86 in a direction perpendicular to both the one direction D1 and the thickness direction DT. Furthermore, in one direction D1, the 19th vibration section 89, the 20th vibration section 90, the 21st vibration section 91, and the 22nd vibration section 92 are arranged in that order.

[0096] Furthermore, the 12th to 22nd vibrating sections 82 to 92 each include a corresponding space, a portion of the second insulating film 482, a portion of the second semiconductor film 502, a piezoelectric film, and an electrode. In addition, the 12th to 22nd vibrating sections 82 to 92 each have 12th to 22nd central axes O12 to O22 and 12th to 22nd resonant frequencies f12 to f22.

[0097] The 12th resonant frequency f12 is, for example, set to 140 kHz. The 13th resonant frequency f13 is, for example, set to 110 kHz. The 14th resonant frequency f14 is, for example, set to 100 kHz. The 15th resonant frequency f15 is, for example, set to 70 kHz. The 16th resonant frequency f16 is, for example, set to 40 kHz. The 17th resonant frequency f17 is, for example, set to 50 kHz. The 18th resonant frequency f18 is, for example, set to 60 kHz. The 19th resonant frequency f19 is, for example, set to 130 kHz. The 20th resonant frequency f20 is, for example, set to 120 kHz. The 21st resonant frequency f21 is, for example, set to 90 kHz. The 22nd resonant frequency f22 is, for example, set to 80 kHz. Note that in Figure 10, the values ​​of the 12th to 22nd resonant frequencies f12 to f22 are indicated so that each resonant frequency can be seen.

[0098] Here, the digital information related to ultrasound stored in the ultrasonic recording medium 32 includes information such as sine waves or cosine waves having the 12th to 22nd resonant frequencies f12 to f22. Therefore, signals such as sine waves or cosine waves having the 12th to 22nd resonant frequencies f12 to f22 are input from the ultrasonic amplification circuit 38 to the 12th to 22nd vibrating units 82 to 92. As a result, as shown in Figure 11, the 12th to 22nd vibrating units 82 to 92 each vibrate with a peak sound pressure value at the 12th to 22nd resonant frequencies f12 to f22.

[0099] Furthermore, the sound pressures at the 12th to 22nd resonant frequencies f12 to f22 are denoted as the 12th to 22nd peak values ​​Pv12 to Pv22, respectively. The average value of the 12th to 22nd peak values ​​Pv12 to Pv22 is set to be 115 dBSPL or less. To achieve this, the size of the space between the 12th to 22nd vibrating sections 82 to 92, the material and thickness of the second insulating film 482, the material and thickness of the second semiconductor film 502, the material and size of the piezoelectric film, and the material and size of the electrodes are all adjusted. In addition, the amplitude of the signal from the ultrasonic amplification circuit 38 is adjusted for this purpose. Note that in Figure 11, the 12th to 22nd peak values ​​Pv12 to Pv22 are set to the same value, but they may be different.

[0100] Furthermore, at this time, difference sound waves are generated between the 1st to 11th vibrating sections 71 to 81 and the 12th to 22nd vibrating sections 82 to 92. Also, the 1st to 11th resonant frequencies f1 to f11 are 40 to 140 kHz, and the 12th to 22nd resonant frequencies f12 to f22 are 40 to 140 kHz. Therefore, the frequency of the difference sound waves generated between the 1st to 11th vibrating sections 71 to 81 and the 12th to 22nd vibrating sections 82 to 92 is 10 to 100 kHz, which includes both audible frequencies and frequencies outside the audible frequency range.

[0101] Furthermore, as shown in Figure 10, the distance from the edge of the first semiconductor substrate 461 to the edge of the second semiconductor substrate 462 in one direction D1 is defined as the substrate distance Lsb. The substrate distance Lsb is greater than the value obtained by dividing the speed of sound by the divisor N. The divisor N is the minimum frequency of the difference sound wave generated between the first to eleventh vibrating parts 71 to 81 located on the first semiconductor substrate 461 and the twelfth to twenty-second vibrating parts 82 to 92 located on the second semiconductor substrate 462, within the frequency range of audible sound.

[0102] Specifically, as described above, the frequency of the difference sound wave generated between the first to eleventh vibrating parts 71 to 81 located on the first semiconductor substrate 461 and the twelfth to twenty-second vibrating parts 82 to 92 located on the second semiconductor substrate 462 is 10 to 100 kHz. Therefore, within the audible frequency range, the minimum value of the difference sound wave frequency generated between the first to eleventh vibrating parts 71 to 81 and the twelfth to twenty-second vibrating parts 82 to 92 is 10 kHz. The speed of sound is approximately 340 m / s. Thus, the distance Lsb between the substrates is greater than 34 mm.

[0103] As described above, the ultrasonic generator 20 of the third embodiment is configured as described above. The ultrasonic generator 20 of the third embodiment also provides the same effects as the second embodiment. Furthermore, the third embodiment also provides the effects described below.

[0104] [3] Here, difference sound waves are generated between the 1st to 11th vibrating sections 71 to 81 and the 12th to 22nd vibrating sections 82 to 92. When the frequency of these generated difference sound waves is the frequency of an audible sound, the sound produced by the difference sound waves is heard by humans in addition to the audible sound emitted from the audible speaker 30. At this time, the sound produced by the difference sound waves becomes noise to humans. For this reason, it is unpleasant to humans, and the hypersonic effect is difficult to obtain.

[0105] Therefore, the distance Lsb between the substrates is greater than the value obtained by dividing the speed of sound by the divisor N. As a result, the distance between the 1st to 11th vibrating sections 71 to 81 and the 12th to 22nd vibrating sections 82 to 92 is greater than one wavelength of the difference sound wave generated between the 1st to 11th vibrating sections 71 to 81 and the 12th to 22nd vibrating sections 82 to 92. Consequently, the difference between the phase of the ultrasound generated in the 1st to 11th vibrating sections 71 to 81 and the phase of the ultrasound generated in the 12th to 22nd vibrating sections 82 to 92 tends to be large. Therefore, the ultrasound generated in the 1st to 11th vibrating sections 71 to 81 and the ultrasound generated in the 12th to 22nd vibrating sections 82 to 92 tend to weaken each other. Thus, the sound pressure of the difference sound wave generated between the 1st to 11th vibrating sections 71 to 81 and the 12th to 22nd vibrating sections 82 to 92 tends to decrease. Therefore, the noise produced by these difference sound waves is suppressed from being perceived as noise by humans, thus reducing discomfort to humans. This makes it easier to achieve the hypersonic effect.

[0106] (Other embodiments) This disclosure is not limited to the embodiments described above, and modifications can be made to these embodiments as appropriate. Furthermore, it goes without saying that, in each of the embodiments described above, the elements constituting the embodiment are not necessarily essential, except in cases where they are explicitly stated to be particularly essential or where they are clearly considered essential in principle.

[0107] The signaling units and methods described herein may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, the signaling units and methods described herein may be implemented by a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. Alternatively, the signaling units and methods described herein may be implemented by one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium.

[0108] In each of the above embodiments, the audible recording medium 22, the audible signal generator 24, the audible playback circuit 26, the audible amplification circuit 28, the ultrasonic recording medium 32, the ultrasonic signal generator 34, the ultrasonic playback circuit 36, and the ultrasonic amplification circuit 38 are all separate components. However, they are not limited to being separate components. For example, the audible recording medium 22, the audible signal generator 24, the audible playback circuit 26, the ultrasonic recording medium 32, the ultrasonic signal generator 34, and the ultrasonic playback circuit 36 ​​may be an integrated circuit. Alternatively, the audible recording medium 22, the audible signal generator 24, the audible playback circuit 26, the audible amplification circuit 28, the ultrasonic recording medium 32, the ultrasonic signal generator 34, the ultrasonic playback circuit 36, and the ultrasonic amplification circuit 38 may be an integrated circuit. In these cases, audible sound and ultrasound are separated via a frequency filter or the like.

[0109] In the embodiments described above, the ultrasonic speaker 40, the first ultrasonic speaker 401, and the second ultrasonic speaker 402 are equipped with a PMUT to generate ultrasonic waves amplified by the ultrasonic amplification circuit 38, but are not limited to this. The ultrasonic speaker 40, the first ultrasonic speaker 401, and the second ultrasonic speaker 402 may, for example, be equipped with a CMUT to generate ultrasonic waves amplified by the ultrasonic amplification circuit 38. CMUT stands for Capacitive Micro-machined Ultrasound Transducer.

[0110] In the third embodiment described above, the distance Lsb between the substrates is greater than the value obtained by dividing the speed of sound by the divisor N. The divisor N is the minimum frequency of the difference sound waves generated between the multiple vibrating parts located on the first semiconductor substrate 461 and the multiple vibrating parts located on the second semiconductor substrate 462, within the frequency range of audible sound. Conversely, the divisor N may be the maximum frequency of the difference sound waves generated between the multiple vibrating parts located on the first semiconductor substrate 461 and the multiple vibrating parts located on the second semiconductor substrate 462, within the frequency range of audible sound.

[0111] This allows the first semiconductor substrate 461 and the second semiconductor substrate 462 to be placed closer together compared to the case where the divisor N is the minimum value mentioned above. As a result, the size of the ultrasonic generator 20 can be reduced. Therefore, an increase in the size of the ultrasonic generator 20 is suppressed. In addition, due to the distance Lsb between the substrates, a difference in phase between the ultrasonic waves generated by the multiple vibrating parts located on the first semiconductor substrate 461 and the ultrasonic waves generated by the multiple vibrating parts located on the second semiconductor substrate 462 is likely to occur. Therefore, the ultrasonic waves generated by the multiple vibrating parts located on the first semiconductor substrate 461 and the ultrasonic waves generated by the multiple vibrating parts located on the second semiconductor substrate 462 tend to weaken each other. As a result, the sound pressure of the difference sound waves generated between the multiple vibrating parts located on the first semiconductor substrate 461 and the multiple vibrating parts located on the second semiconductor substrate 462 tends to decrease. Therefore, the sound from these difference sound waves is less likely to become noise to humans, thus reducing discomfort to humans. This makes it easier to obtain the hypersonic effect.

[0112] The above embodiments may be combined as appropriate. [Explanation of Symbols]

[0113] 30 Audible Speakers 38. Amplifier circuit for ultrasonic applications 40 ultrasonic speakers 71 First Vibration Section 72 Second Vibration Section f1 1st resonance frequency f2 2nd resonant frequency fd Difference frequency

Claims

1. An ultrasonic generator, an audible sound irradiating unit (30) that irradiates a person with audible sound, An ultrasonic irradiation unit (40, 401) including a first vibrating unit (71) having a first resonant frequency (f1) and a second vibrating unit (72) having a second resonant frequency (f2), A signal unit (38) that outputs a signal including the first resonant frequency and the second resonant frequency to the first vibrating unit and the second vibrating unit, Equipped with, When a signal including the first resonant frequency and the second resonant frequency is input to the first vibrating unit and the second vibrating unit, The first vibrating unit generates ultrasonic waves by vibrating with a sound pressure peak value at the first resonant frequency, and irradiates the person with the generated ultrasonic waves. The second vibrating unit generates ultrasonic waves by vibrating with a sound pressure peak value at the second resonant frequency, and irradiates the person with the generated ultrasonic waves. The vibration of the first vibrating part and the second vibrating part generates a difference sound wave with a difference frequency (fd, fd1) represented by the absolute value of the difference between the first resonant frequency and the second resonant frequency. The aforementioned difference tone frequency is considered to be the frequency of an audible sound. An ultrasonic generator in which the average value of the sound pressure at the first resonant frequency and the sound pressure at the second resonant frequency is 115 dBSPL or less.

2. The ultrasonic generator according to claim 1, wherein the average value of the sound pressure at the first resonant frequency and the sound pressure at the second resonant frequency is 105 dBSPL or less.

3. The ultrasonic generator according to claim 1 or 2, wherein the distance (Lp, Lp1) from the center (O1) of the first vibrating part to the center (O2) of the second vibrating part is less than or equal to the value (λp) obtained by dividing the speed of sound (c) by the difference tone frequency.

4. The ultrasonic irradiation unit is a first ultrasonic irradiation unit (401), The ultrasonic generating device further comprises a second ultrasonic irradiation unit (402) which includes a third vibrating unit (73) having a third resonant frequency (f3) and a fourth vibrating unit (74) having a fourth resonant frequency (f4). The signal unit outputs signals including the third resonant frequency and the fourth resonant frequency to the third vibration unit and the fourth vibration unit. When a signal including the third resonant frequency and the fourth resonant frequency is input to the third vibrating unit and the fourth vibrating unit, The third vibrating part generates ultrasonic waves by vibrating with a sound pressure of the third resonant frequency as its peak value, and irradiates the person with the generated ultrasonic waves. The fourth vibrating part generates ultrasonic waves by vibrating with a sound pressure of the fourth resonant frequency as its peak value, and irradiates the person with the generated ultrasonic waves. The vibration of the first vibrating part and the third vibrating part generates a difference sound wave of a first frequency (|f1 - f3|) which is represented by the absolute value of the difference between the first resonant frequency and the third resonant frequency. The vibration of the first vibrating part and the fourth vibrating part generates a difference sound wave of a second frequency (|f1-f4|) which is represented by the absolute value of the difference between the first resonant frequency and the fourth resonant frequency. The vibrations of the second and third vibrating parts generate a difference sound wave of a third frequency (|f2 - f3|) which is represented by the absolute value of the difference between the second resonant frequency and the third resonant frequency. The vibrations of the second and fourth vibrating parts generate a difference sound wave of a fourth frequency (|f2 - f4|) which is represented by the absolute value of the difference between the second resonant frequency and the fourth resonant frequency. The first frequency, the second frequency, the third frequency, and the fourth frequency are defined as audible sound frequencies. The distance (Ls1) from the center (O1) of the first vibrating part to the center (O3) of the third vibrating part is greater than the value obtained by dividing the speed of sound (c) by the first frequency (c / |f1-f3|), The distance (Ls2) from the center (O1) of the first vibrating part to the center (O4) of the fourth vibrating part is greater than the value obtained by dividing the speed of sound (c) by the second frequency (c / |f1-f4|), The distance (Ls3) from the center (O2) of the second vibrating part to the center (O3) of the third vibrating part is greater than the value obtained by dividing the speed of sound (c) by the third frequency (c / |f2-f3|), The ultrasonic generator according to claim 1, wherein the distance (Ls4) from the center (O2) of the second vibrating part to the center (O4) of the fourth vibrating part is greater than the value obtained by dividing the speed of sound (c) by the fourth frequency (c / |f2-f4|).

5. The ultrasonic irradiation unit is a first ultrasonic irradiation unit (401), The first ultrasonic irradiation unit includes a first substrate (461) on which the first vibrating unit and the second vibrating unit are arranged. The ultrasonic generating device further comprises a second ultrasonic irradiation unit (402) which includes a 12th vibrating unit having a 12th resonant frequency, a 13th vibrating unit having a 13th resonant frequency, and a second substrate (462) on which the 12th vibrating unit and the 13th vibrating unit are arranged. The signal unit outputs a signal including the 12th resonant frequency and the 13th resonant frequency to the 12th vibration unit and the 13th vibration unit. When a signal including the 12th resonant frequency and the 13th resonant frequency is input to the 12th vibrating unit and the 13th vibrating unit, The 12th vibrating part generates ultrasonic waves by vibrating with a sound pressure of the 12th resonant frequency as its peak value, and irradiates the person with the generated ultrasonic waves. The 13th vibrating unit generates ultrasonic waves by vibrating with a sound pressure of the 13th resonant frequency as its peak value, and irradiates the person with the generated ultrasonic waves. The frequency of the difference sound wave generated between the first vibrating part and the second vibrating part and the twelfth vibrating part and the thirteenth vibrating part includes the frequency of audible sound. The first substrate and the second substrate are arranged in one direction (D1), The ultrasonic generator according to claim 1, wherein the distance (Lsb) from the edge of the first substrate to the edge of the second substrate in one direction is greater than the value obtained by dividing the speed of sound by the minimum value (N) of the difference sound wave frequencies generated between the first vibrating part and the second vibrating part, which are located on the first substrate and the twelfth vibrating part and the thirteenth vibrating part, which are located on the second substrate, within the range of audible sound frequencies.

6. The ultrasonic irradiation unit is a first ultrasonic irradiation unit (401), The first ultrasonic irradiation unit includes a first substrate (461) on which the first vibrating unit and the second vibrating unit are arranged. The ultrasonic generating device further comprises a second ultrasonic irradiation unit (402) which includes a 12th vibrating unit having a 12th resonant frequency, a 13th vibrating unit having a 13th resonant frequency, and a second substrate (462) on which the 12th vibrating unit and the 13th vibrating unit are arranged. The signal unit outputs a signal including the 12th resonant frequency and the 13th resonant frequency to the 12th vibration unit and the 13th vibration unit. When a signal including the 12th resonant frequency and the 13th resonant frequency is input to the 12th vibrating unit and the 13th vibrating unit, The 12th vibrating part generates ultrasonic waves by vibrating with a sound pressure of the 12th resonant frequency as its peak value, and irradiates the person with the generated ultrasonic waves. The 13th vibrating unit generates ultrasonic waves by vibrating with a sound pressure of the 13th resonant frequency as its peak value, and irradiates the person with the generated ultrasonic waves. The frequency of the difference sound wave generated between the first vibrating part and the second vibrating part and the twelfth vibrating part and the thirteenth vibrating part includes the frequency of audible sound. The first substrate and the second substrate are arranged in one direction (D1), The ultrasonic generator according to claim 1, wherein the distance (Lsb) from the edge of the first substrate to the edge of the second substrate in one direction is greater than the value obtained by dividing the speed of sound by the maximum value (N) of the difference sound wave frequencies generated between the first vibrating part and the second vibrating part, which are located on the first substrate and the twelfth vibrating part and the thirteenth vibrating part, which are located on the second substrate, within the range of audible sound frequencies.

7. The frequency of the difference sound wave generated by the vibration of the third and fourth vibrating parts is set to the frequency of an audible sound. The ultrasonic generator according to claim 4, wherein the average value of the sound pressure at the third resonant frequency and the sound pressure at the fourth resonant frequency is 115 dBSPL or less.

8. The ultrasonic generator according to claim 1 or 2, wherein the first resonant frequency and the second resonant frequency are 40 kHz or more and 140 kHz or less.

9. The frequency of the difference sound wave generated by the vibration of the 12th vibrating part and the 13th vibrating part is the frequency of an audible sound, The ultrasonic generator according to claim 5 or 6, wherein the average value of the sound pressure at the 12th resonant frequency and the sound pressure at the 13th resonant frequency is 115 dBSPL or less.

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