Ultrasonic generator

Abstract

The ultrasonic generator 10 includes a loudspeaker element 51 having a first resonant frequency f1 and a loudspeaker element 52 having a second resonant frequency f2. The first resonant frequency f1 and the second resonant frequency f2 are adjacent resonant frequencies in the loudspeaker 10. The distance L between the elements is set such that the sound from the first loudspeaker element and the sound from the second loudspeaker element have a predetermined relationship at a target location. The target location is two or more locations on an object in a target space. The predetermined relationship is that the sound from the first loudspeaker element and the sound from the second loudspeaker element reinforce each other at an intermediate frequency fmid between the first resonant frequency f1 and the second resonant frequency f2.

Description

[0001] Intersection of related applications

[0002] This application claims priority to Japanese Patent Application No. 2021-132927, filed on August 17, 2021, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to an ultrasonic generator. Background Technology

[0004] Patent Document 1 discloses an invention of an ultrasonic transducer and an ultrasonic diagnostic device. This type of ultrasonic generator requires broadband characteristics to produce broadband sound waves. In the case of a device having multiple piezoelectric cells with different resonant frequencies, the device in Patent Document 1 performs phase matching between the piezoelectric cells to obtain broadband characteristics. The disclosures of prior art documents are incorporated herein by reference to explain the technical elements appearing herein.

[0005] Existing technical documents

[0006] Patent documents

[0007] [Patent Document 1] JP2019-76122A Summary of the Invention

[0008] Ultrasonic generators typically need to produce broadband ultrasonic waves. Furthermore, they are required to deliver sound waves with high sound pressure levels to the target space. In light of these considerations, or others not mentioned, ultrasonic generators require further improvement.

[0009] One object of this disclosure is to provide an ultrasonic generator that provides strong sound pressure over a wide frequency band.

[0010] This disclosure provides an ultrasonic generator for emitting sound waves toward a target space, comprising: a plurality of loudspeaker elements, which are piezoelectric MEMS ultrasonic transducers, wherein the plurality of loudspeaker elements include: a first loudspeaker element having a first resonant frequency; and a second loudspeaker element having a second resonant frequency adjacent to the first resonant frequency, wherein the first loudspeaker element and the second loudspeaker element are arranged separately from each other in a direction intersecting the direction toward the target space, and wherein the distance between the first loudspeaker element and the second loudspeaker element is set such that an enhancement relationship of sounds from the first loudspeaker element and the second loudspeaker element having an intermediate frequency appears at two or more locations on an object located in the target space, and wherein the enhancement relationship is created by enhancing the sound from the first loudspeaker element having an intermediate frequency between the first resonant frequency and the second resonant frequency and the sound from the second loudspeaker element having the intermediate frequency.

[0011] According to the ultrasonic generator disclosed herein, it is possible to obtain a reinforcement relationship of intermediate frequency sound at two or more locations on an object. As a result, an ultrasonic generator that provides strong sound pressure levels over a wide frequency band is provided. Furthermore, it is possible to provide strong sound pressure levels to the object even if its position changes.

[0012] The aspects disclosed in this specification employ different technical solutions to achieve their respective purposes. The reference numerals enclosed in parentheses in the claims and those described in this section exemplarily illustrate the correspondence with portions of the embodiments described later, and are not intended to limit the scope of the technology. The purposes, features, and effects disclosed herein are further elucidated with reference to the following detailed description and accompanying drawings. Attached Figure Description

[0013] Figure 1 This is a block diagram of an ultrasonic system according to the first embodiment.

[0014] Figure 2 This is a front view of an ultrasonic generator.

[0015] Figure 3 This is a graph showing the frequency characteristics of an ultrasonic generator.

[0016] Figure 4 It is a plan view showing the ultrasonic generator and the target space.

[0017] Figure 5 This is a table showing the formulas.

[0018] Figure 6 This is a front view showing an example of the target space.

[0019] Figure 7 It is a front view showing the relationship between the object and the locations where sound pressure reinforces each other.

[0020] Figure 8 This is a table showing an example of the value 2z for the distance between elements.

[0021] Figure 9 It is a graph showing the relationship between the distance to the target space and the distance between the components.

[0022] Figure 10 This is a block diagram of an ultrasonic system according to the second embodiment.

[0023] Figure 11 This is a front view of an ultrasonic generator.

[0024] Figure 12 This is a block diagram of an ultrasonic system according to the third embodiment.

[0025] Figure 13 This is a front view of an ultrasonic generator.

[0026] Figure 14 This is a front view of the ultrasonic generator according to the fourth embodiment.

[0027] Figure 15 This is a front view showing an example of the target space.

[0028] Figure 16 This is a front view of the ultrasonic generator according to the fifth embodiment.

[0029] Figure 17 This is a front view of the ultrasonic generator according to the sixth embodiment. Detailed Implementation

[0030] Several embodiments are described with reference to the accompanying drawings. In some embodiments, functionally and / or structurally corresponding and / or associated elements may be given the same reference numerals, or reference numerals with different numbers at or above the hundreds place. Corresponding and / or associated portions can be referred to in the description of other embodiments.

[0031] First Embodiment

[0032] exist Figure 1In this embodiment, ultrasonic system 1 is a device that provides sound toward target spaces TR1 and TR2. Objects exist within target spaces TR1 and TR2. In this embodiment, target spaces TR1 and TR2 can also be referred to as indoor spaces. Specifically, target spaces TR1 and TR2 are the interior of vehicle 2. Target space TR1 is a space with height HD1 and depth DD1. Target space TR2 is a space with height HD2 and depth DD2. Target space TR2 is larger than target space TR1. Target spaces TR1 and TR2 are examples used to illustrate the embodiment. Ultrasonic system 1 may include a single target space. Ultrasonic system 1 may include three or more target spaces.

[0033] In this specification, the term "vehicle 2" should be interpreted broadly. Vehicle 2 includes automobiles, airplanes, ships, spacecraft, etc. Furthermore, vehicle 2 includes devices that do not involve movement, such as simulation devices and entertainment devices for carrying people. Vehicle 2 and target spaces TR1 and TR2 can be defined in three dimensions. In the following description, names such as forward direction FR, backward direction RR, right direction RT, left direction LT, upward direction UP, and downward direction DW may be used. Target spaces TR1 and TR2 can be defined by the maximum width WM in the width direction WD, the maximum height HM in the height direction HD, and the maximum depth DM in the depth direction DD. These names are for ease of understanding and not for limiting this disclosure.

[0034] Ultrasonic system 1 provides a predetermined sound to an object. In other words, ultrasonic system 1 reproduces the predetermined sound on the surface and / or inside the object. Ultrasonic system 1 is a device that alters the properties of an object through sound. An example of an object is a living organism. Ultrasonic system 1 is a device that produces a predetermined biological response by providing a predetermined sound to an organism. In other words, ultrasonic system 1 is a device that exerts a predetermined effect on an organism by reproducing the predetermined sound on the surface and / or inside the organism. The object in target spaces TR1 and TR2 can be a human being. In this case, ultrasonic system 1 is a device that provides sound to a human being.

[0035] In recent years, attempts have been made to utilize devices that employ sound rich in ultra-high frequency components exceeding the upper limit of audible frequencies. One such device delivers audible sound to the human ear and applies ultrasound waves to the body. In this endeavor, for example, efforts are being made to increase alpha waves in the brain. For instance, attempts are being made to achieve effects such as increased sensitivity, stress reduction, optimization of the autonomic nervous system, optimization of the endocrine system, and / or optimization of the immune system. This effect is also known as the hypersonic effect. To develop a hypersonic effect in the human body, it is necessary to radiate hypersonic sound containing ultra-high frequency components onto the surface of the body.

[0036] The ultrasonic generator 10 used for this purpose may be referred to by names such as ultrasonic loudspeaker or ultrasonic transducer. The ultrasonic generator 10 emits sound waves toward target spaces TR1 and TR2. In the following description, the ultrasonic generator 10 will be referred to as loudspeaker 10. The ultra-high frequency component includes at least a portion of a wide bandwidth extending from a lower limit frequency of 40 kHz to an upper limit frequency exceeding 100 kHz. In one example, the ultra-high frequency component may extend over a wide bandwidth from a lower limit frequency of 40 kHz to an upper limit frequency of 140 kHz. The loudspeaker 10 needs to reproduce hypersonic sound on the human body surface with a small sound pressure level difference.

[0037] The ultrasonic system 1 includes a loudspeaker 10 that generates broadband sound. The ultrasonic system 1 also includes circuitry 21 that serves as a sound source 20 providing a sound source signal to the loudspeaker 10. The ultrasonic system 1 has a circuitry configuration suitable for the shape of the application environment, such as target spaces TR1 and TR2. The applicable circuitry configuration includes the configuration of circuitry 21 and the number of loudspeakers 10. The ultrasonic system 1 of this embodiment has a circuitry configuration assuming the user of the vehicle 2 is the object. Circuitry 21 includes a hypersonic sound generator circuit, multiple phase adjustment circuits, multiple amplifier circuits, and multiple piezoelectric element drive circuits. The configuration of these circuitry elements is described by reference to JP2019-76122A.

[0038] Loudspeaker 10 emits ultrasonic waves toward a target space and reproduces hypersonic sound in the target space at a predetermined sound pressure level. Loudspeaker 10 is characterized by multiple indicators that indicate its performance (e.g., directivity and output). These indicators include the effective distance at which the desired sound pressure level can be reproduced. In this embodiment, the ultrasonic system 1 includes multiple loudspeakers 11 and 12 to deliver the predetermined sound over a large area within a room.

[0039] The ultrasonic system 1 includes a first loudspeaker 11. The first loudspeaker 11 is designed for a target space TR1, which is the space where a user, assuming the driver's seat, is located. The first loudspeaker 11 emits sound waves in a main sound wave direction TD1. The sound wave direction TD1 is directed towards the space from the assumed driver's head to their chest. The first loudspeaker 11 can be intended for a person sitting in the front seat. In this case, the first loudspeaker 11 can cover the area of ​​the front seat, including both the driver's seat and the passenger seat, which is the target space.

[0040] The ultrasonic system 1 includes a second speaker 12. The second speaker 12 is designed for a target space TR2, which is the space where a user in the back seat is assumed to be located. The second speaker 12 has a main sound wave direction TD2. The sound wave direction TD2 is directed towards the space from the head to the chest of the user in the back seat.

[0041] For example, ultrasonic system 1 can provide different sounds to users in target space TR1 and target space TR2. For instance, since the driver in the driver's seat, who is involved in driving the vehicle 2, requires a high level of arousal, ultrasonic system 1 is expected to enhance arousal. Conversely, rear-seat users who are not directly involved in driving seek comfort. In this case, ultrasonic system 1 is expected to provide comfort to the rear-seat users. Ultrasonic system 1 can also provide the same sound to users in target space TR1 and target space TR2.

[0042] The first speaker 11 and the second speaker 12 have the same configuration. In the following description, the speaker 10 may be described without distinguishing between the first speaker 11 and the second speaker 12.

[0043] exist Figure 2In this embodiment, the loudspeaker 10 includes at least one container 30 and at least one semiconductor element 40. The loudspeaker 10 may include a single container 30 or multiple containers 30. A single container 30 may contain a single semiconductor element 40 or multiple semiconductor elements 40. Each of the multiple containers 30 may contain a semiconductor element 40, described later, or a loudspeaker 10 may be provided as a group. The loudspeaker 10 may include a single semiconductor element 40 or multiple semiconductor elements 40. A single semiconductor element 40 may include multiple loudspeaker elements having adjacent resonant frequencies f1 and f2, which will be described later. Each of the multiple semiconductor elements 40 may include multiple loudspeaker elements having adjacent resonant frequencies f1 and f2, which will be described later. Among the multiple semiconductor elements 40, one semiconductor element 40 may include a loudspeaker element having a resonant frequency f1, while another semiconductor element 40 may include a loudspeaker element having a resonant frequency f2. In this embodiment, the loudspeaker 10 includes a single container 30 and a single semiconductor element 40.

[0044] Semiconductor element 40 is housed within the container. Semiconductor element 40 is also referred to as a MEMS element (MEMS: MicroElectro Mechanical Systems). Semiconductor element 40 is formed using MEMS-related technologies.

[0045] Semiconductor element 40 has a semiconductor substrate 41. Semiconductor substrate 41 is a single semiconductor substrate made of a continuous material. Semiconductor substrate 41 is made of, for example, Si. Semiconductor substrate 41 has a plurality of loudspeaker elements 50. Loudspeaker elements 50 include a plurality of loudspeaker elements 51 and 52. In other words, both the first loudspeaker element 51 and the second loudspeaker element 52 are formed on a common semiconductor substrate 41. In the figures, two loudspeaker elements 51 and 52 are shown as typical examples. A loudspeaker element 50 includes a resonant plate region 50a and a piezoelectric element 50b. The resonant plate region 50a is characterized by various characteristics that resonate at a predetermined resonant frequency. These characteristics include material-dependent properties and mechanical shape-dependent properties such as area, thickness, etc. The piezoelectric element 50b is electrically connected to a circuit 21. The piezoelectric element 50b vibrates at a predetermined frequency in response to a signal supplied from the circuit 21. The resonant plate region 50a resonates with the piezoelectric element 50b and emits sound waves with a predetermined frequency. The loudspeaker element 50 is also known as a PMUT (Piezoelectric Micro-machined Ultrasonic Transducer). The loudspeaker element 50 is also referred to as a piezoelectric MEMS ultrasonic transducer.

[0046] In the ultrasonic system 1, the first speaker element 51 and the second speaker element 52 are correlated with each other by having two adjacent resonance frequencies. As an example, the first speaker element 51 has a resonance frequency of a first frequency f1 = 40 kHz. The second speaker element 52 has a resonance frequency of a second frequency f2 = 50 kHz. The difference f2 - f1 between the two adjacent resonance frequencies is set within a range of several kHz to 50 kHz. In the present embodiment, the difference f2 - f1 between the two adjacent resonance frequencies is 10 kHz. In another embodiment, the first speaker element 51 has a resonance frequency of a first frequency f1 = 130 kHz, and the second speaker element 52 has a resonance frequency of a second frequency f2 = 140 kHz. In the present embodiment, the first frequency f1 is less than the second frequency f2 (f1 < f2). The first speaker element 51 and the second speaker element 52 form a speaker pair 60.

[0047] The first speaker element 51 and the second speaker element 52 are arranged separately from each other in a direction (central axis AXz described later) intersecting with the direction (central axis AXy described later) toward the target spaces TR1 and TR2. The first speaker element 51 and the second speaker element 52 are separated by a distance L in the direction of the central axis AXz passing through the centers of the two speaker elements 50. In the present embodiment, the central axis AXz is perpendicular to the direction of gravity. The central axis AXz is also a horizontal line.

[0048] Assume that the midpoint M is located at the midpoint between the two speaker elements 51 and 52. In this case, the distance between the midpoint M and one speaker element 50 is L / 2 = z. In the following description, the theoretical value of the distance L can be represented by the value 2z. The value 2z is also the minimum value of the distance L between the elements. The value 2z is the minimum distance between the two speaker elements 51 and 52 having two adjacent resonance frequencies in the ultrasonic system 1.

[0049] The first speaker element 51 and the second speaker element 52 are arranged at one end and the other end of the semiconductor substrate 41. This arrangement makes it possible to make the distance L as large as possible by maximizing the use of the size of the semiconductor substrate 41. In other words, it is possible to provide the desired distance L with a small semiconductor substrate 41. Therefore, in many cases, the maximum value of the distance L depends on the size of the semiconductor substrate 41.

[0050] Figure 3 It is a graph with the horizontal axis being the frequency f kHz and the vertical axis being the sound pressure SP (dBSPL). Figure 3The sound pressure levels (SPL) curves on the frequency axis are displayed. The SPL curve SP51 of the sound produced by the first loudspeaker element 51 has a peak at the first frequency f1. The SPL curve SP52 of the sound produced by the second loudspeaker element 52 has a peak at the second frequency f2. An intermediate frequency fmid (fmid = (f1 + f2) / 2) between the first frequency f1 and the second frequency f2 can be assumed. The SPL at the intermediate frequency fmid depends on the phase difference between the phase of the sound from the first loudspeaker element 51 and the phase of the sound from the second loudspeaker element 52. For example, a dip is produced when the sounds cancel each other out, and a peak is produced when the sounds are amplified.

[0051] When the first loudspeaker element 51 and the second loudspeaker element 52 are arranged close to each other, this arrangement can be considered a point source. In this case, if there is a phase difference of half the wavelength λ at the mid-frequency fmid, a trough appears at the mid-frequency fmid. Furthermore, when both loudspeaker elements are considered as point sources, the sound at the mid-frequency fmid becomes a trough at all locations in the target space. In this case, peaks and troughs are observed alternately along the frequency axis at all locations in the target space. As a result, it is difficult to obtain a uniform sound pressure level without troughs over a wide frequency band.

[0052] In this embodiment, the distance L is set and designed such that the sound at the mid-frequency fmid does not cause dips at multiple locations in the target space. The distance L is set to create positions where the sound at the mid-frequency fmid reinforces each other at two or more locations on the object. In this embodiment, it is assumed that the central axis AXy passes through the midpoint M and the center point of the object. Therefore, assuming a region starting from the center point of the object on one side, the distance L is set to create positions where the sound at the mid-frequency fmid reinforces each other at one or more locations on the object. Positions where the mid-frequency fmid reinforces each other are created due to the different distances to the two speaker elements. In this embodiment, the distance L is set and designed such that the sound reinforces each other at the mid-frequency fmid. The distance L can be set to be equal to or greater than the theoretically required minimum value 2z.

[0053] like Figure 3As shown, at the mid-frequency fmid, a peak PKfmid, lower than the peak PK51 of sound pressure curve SP51 or the peak PK52 of sound pressure curve SP52, can be observed. The sound pressure of this peak PKfmid (dashed line) is stronger than the sound pressure (solid line) obtained through sound pressure curves SP51 or SP52. As a result, a uniform sound pressure characteristic without obvious valleys can be obtained across a wide frequency band. In this embodiment, a uniform sound pressure characteristic without obvious valleys was obtained across a wide frequency band including the vicinity of frequency f1, the vicinity of frequency f2, and the frequency between f1 and f2. No obvious peaks are observed near the mid-frequency fmid. A substantially uniform sound pressure can be obtained near the mid-frequency fmid. In other words, a gradually increasing or decreasing sound pressure characteristic can be obtained near the mid-frequency fmid. A uniform sound pressure is obtained across a relatively wide frequency band near the mid-frequency fmid.

[0054] According to this embodiment, it is possible to avoid suppressing the sound of the intermediate frequency fmid at all locations in the target space. In this embodiment, the sound of the intermediate frequency fmid is reproduced at high sound pressure levels at multiple locations in the target space. As a result, a uniform sound pressure distribution without obvious valleys is achieved. From one perspective, the distance L between two loudspeaker elements having adjacent resonant frequencies is set such that multiple peaks of the intermediate frequency fmid are observed in the target space. The wavelength of the intermediate frequency fmid is also called the intermediate wavelength λmid. From one perspective, the distance L is set to be equal to or greater than the intermediate wavelength λmid. From another perspective, the distance L is set to be sufficiently greater than the intermediate wavelength λmid. The two loudspeaker elements defining the distance L are arranged to be sufficiently far apart from each other relative to the intermediate wavelength λmid.

[0055] Figure 4This diagram illustrates the positional relationship between two speaker elements 51 and 52 and the target space TR. The sound wave direction TD of speaker elements 51 and 52 points towards the target space TR. Assume that sound is supplied from speaker elements 51 and 52 to the target position TG. Speaker elements 51 and 52 are separated from the target position TG by a distance y on the central axis AXy of the sound wave direction TD. The central axis AXy passes through the midpoint between the first speaker element 51 and the second speaker element 52. Assume that the first speaker element 51 or the second speaker element 52 is separated from the central axis AXy by a distance z on the central axis AXz. Therefore, the first speaker element 51 and the second speaker element 52 are separated by a value of 2z on the central axis AXz. The target position TG and the central axis AXy are separated by a distance x on the axis AXw. The axis AXw is an axis parallel to the central axis AXz. The axis AXw extends in the width direction WD of the target space TR. The first speaker element 51 is separated from the target position TG by a distance dL. The second speaker element 52 is separated from the target position TG by a distance dH.

[0056] Given this positional relationship, the value 2z can be set by evaluating the acoustic interference at the target location TG. In other words, the value 2z is set such that the intermediate frequency sound reinforces each other at two or more locations on the object. The value 2z is the minimum value that satisfies the above condition.

[0057] Figure 5 It shows from Figure 4 Several mathematical equations are derived from the positional relationship. The resonant frequency (center frequency) of the first loudspeaker element 51 is frequency f1. The resonant frequency (center frequency) of the second loudspeaker element 52 is frequency f2. The intermediate frequency fmid is given by equation (1) (fmid = (f1 + f2) / 2). The intermediate wavelength λmid is given by equation (2) (λmid = (λ1 + λ2) / 2). The relationship between the intermediate frequency fmid and the intermediate wavelength λmid is expressed by equation (3). Note that c is the speed of sound.

[0058] The reinforcement relationship between the sound from the first loudspeaker element 51 and the sound from the second loudspeaker element 52 at the target position TG is obtained based on the wavelength λ and the distance difference Δd through equation (4) (nλmid=Δd+λmid / 2). n is the order. The distance difference Δd is given by equation (5) (Δd=dH-dL). The distance dH is given by equation (6) (dH=SQRT((z+x)) 2 +y 2 The distance dL is given by equation (7) (dL=SQRT((zx)). 2 +y 2 The value of SQRT(X) is given. SQRT(X) represents the square root of X. For the velocity of sound c, the value of equation (8) can be used.

[0059] From equation (4) above, we can obtain equation (9) representing the order n (n=(SQRT((z+x))). 2 +y 2 )-SQRT((zx) 2 +y 2 )) / λmid+1 / 2). The order n is a natural number. The order n can be set to be equal to or greater than 1. The order n affects the number of positions appearing within a predetermined distance from the central axis AXy among multiple positions where a mutually reinforcing relationship between two sounds can be obtained. In this embodiment, the distance L is set to be equal to or greater than the value 2z, which can be obtained by equation (9) (n=(SQRT((z+x)) 2 +y 2 )-SQRT((zx) 2 +y 2 The value is obtained as )) / λmid+1 / 2). Here, n is a natural number of 1 or greater, z is the distance between the midpoint of the two speaker elements and the speaker elements, x is the width of the object, and y is the distance between the midpoint and the object.

[0060] From equation (9) above, equation (10) (2z / λmid = C(y)) can be obtained. The coefficient C(y) represents the coefficient when the distance y is fixed. The coefficient C(y) depends on the intermediate wavelength λmid. The coefficient C(y) represents the relationship between the value 2z and the intermediate wavelength λmid. By modifying equation (10), equation (11) (2z = C(y) × λmid) is obtained. When the distance y is determined, the value obtained by multiplying the intermediate wavelength λmid by the coefficient C(y) is taken as the value 2z. Equation (11) gives the minimum value 2z of the distance L. In this embodiment, the distance L is set as if the object is a human face. The distance L is set to be equal to or greater than the value 2z obtained from equation (11) (2z = 0.85 × λmid).

[0061] The distance y varies depending on the application of the ultrasonic system 1. However, in applications that generate sound, the distance y between the speaker element 50 and the target position TG is considered to be 100 mm or greater. Furthermore, the maximum value of the distance y is limited by the upper limit of the output of the speaker 10. The maximum value of the distance y can be set to approximately 2000 mm. The maximum value of the distance y is proportional to the maximum value of the output of the speaker 10. The maximum value of the distance y can be assumed to be between approximately 2000 mm and 8000 mm. Assuming the ultrasonic system 1 is used in the vehicle in this embodiment, the maximum distance y at which the speaker 10 can effectively reproduce sound can be considered to be approximately 5000 mm.

[0062] Figure 6The diagram illustrates the setting conditions for the positions where two sounds can be obtained in this embodiment, where they reinforce each other. The illustration shows the case of speaker 11. This case assumes a person is an object existing in the target space TR. Speaker 10 reproduces hypersonic sound on the living surface of the object. The exposed biological surface of the person can be selected as the part that perceives the sound. In this case, the periphery of the person's face, neck, and chest can be selected as the part that perceives the sound. In this case, the center of the target position TG is set around the person's chin.

[0063] Figure 6 The diagram shows the reinforcement relationship PL(m) relative to the intermediate wavelength λmid, in which two sounds reinforce each other. A first reinforcement relationship from the central axis AXy is obtained along the relationship line PL(1) intersecting the central axis AXz. A second reinforcement relationship from the central axis AXy is obtained along the relationship line PL(2) intersecting the central axis AXz. Relationship lines PL(1) and PL(2) are part of a curve. The reinforcement relationship occurs at two or more locations on an object located in the target space. A sound from the first loudspeaker element 51 with an intermediate frequency fmid and a sound from the second loudspeaker element 52 with an intermediate frequency fmid reinforce each other with the aforementioned reinforcement relationship. The distance L between the first loudspeaker element 51 and the second loudspeaker element 52 is set such that the aforementioned reinforcement relationship occurs at two or more locations on the object.

[0064] Since the object's position is not fixed, it varies depending on the person's posture. Assuming a face, it can be considered to have a width of 2x in the width direction WD. This distance 2x is set based on the distance x from the central axis AXy in the width direction WD. For example, in the case of a Japanese adult, distance x can be set to approximately 73mm. Any statistical value can be used as the value for distance x. For example, 73mm is given as a statistical value for Japanese people aged 18 to 30.

[0065] Multiple relation lines PL(m) are generated on the surface of the object. This allows for substantially uniform sound to act on the surface of the object. In other words, multiple relation lines PL(m) are manifested on the surface of the object. As a result, sound with sound pressure levels without valleys can be applied to the surface of the object. In this embodiment, hypersonic sound with sound pressure levels without valleys can be applied to a human face.

[0066] Furthermore, in this embodiment, multiple reinforcement relationships PL(m) are manifested on the surface of the object. In the illustrated example, at least two reinforcement relationships PL(m) are manifested on the surface of the object. Thus, even if the object moves, at least one reinforcement relationship PL(m) can be manifested on the surface of the object. Specifically, at least one reinforcement relationship PL(m) is manifested on one half of the face. At least one reinforcement relationship PL(1) is manifested in the right half of the face. At least one reinforcement relationship PL(1) is also manifested in the left half of the face. As a result, even if the object moves within a width (distance 2x), the sound pressure obtained through the reinforcement relationship PL(1) can be applied to the object.

[0067] Figure 7 Multiple reinforcement points PS and multiple deflection points PW are shown. A human face is illustrated as an object. Solid lines indicate the specified positions of the object (face). Defined positions represent, for example, positions in a normal sitting posture. Dashed lines indicate the maximum displacement of the hypothetical object (face). In this example, the maximum displacement SH is one object (face) (SH = 2x). In this embodiment, the value 2z is set such that at least two reinforcement points PS appear on the surface of the object. As a result, hypersonic sound can be strongly applied even if the position of the object fluctuates.

[0068] The upper part shows an example of at least two reinforcement points PS appearing on the surface of an object. The upper part shows an example of order n=1. At least one reinforcement point PS appears on one half of the face. Also in this example, the reinforcement relationship PS appears at two locations on the object located in the target space. The sound from the first speaker element 51 with a mid-frequency fmid and the sound from the second speaker element 52 with a mid-frequency fmid reinforce each other with the reinforcement relationship PS. In this example, even if the face moves laterally (left and right), one reinforcement point PS still appears on the face. Furthermore, at all locations where the face moves from a specified position to the maximum movement position, one reinforcement point PS continues to appear on the face.

[0069] The lower half shows an example of at least four reinforcement points PS on the surface of an object. The lower half shows an example of order n=2. At least two reinforcement points PS are represented on one half of a face. Also in this example, reinforcement PS appear at four locations on the object located in the target space. Sounds from the first speaker element 51 with an intermediate frequency fmid and sound from the second speaker element 52 with an intermediate frequency fmid mutually reinforce each other with reinforcement PS. In this example, even if the face moves, one reinforcement point PS still appears on the face. Furthermore, one or more reinforcement points PS appear on the face at all locations where the face moves from a specified position to a maximum movement position.

[0070] Figure 8 The numerical value of 2z embodied in the structure of this embodiment is shown. This example is an example of order n=1. This example assumes a human face as the object. Therefore, the distance x is 73mm. It is assumed that the effective range of distance y is a minimum distance y equal to or greater than 100mm, and a maximum distance y equal to or less than 2000mm. The value 2z represents the cases where the intermediate frequency fmid is fmid=45kHz and the cases where the intermediate frequency fmid is fmid=135kHz. In the case of intermediate frequency fmid=45kHz, the first speaker element 51 has a resonant frequency f1=40kHz, and the second speaker element 52 has a resonant frequency f2=50kHz. In the case of intermediate frequency fmid=135kHz, the first speaker element 51 has a resonant frequency f1=130kHz, and the second speaker element 52 has a resonant frequency f2=140kHz.

[0071] Figure 9 This is a graph showing the relationship between the coefficient C(y) and the order n. At the mid-wavelength λmid, the minimum value 2z is given by equation (11). For example, the value 2z of the distance between the first speaker element 51 and the second speaker element 52 with a mid-frequency fmid of 45kHz is 2z = C(y) × λmid = 0.85 × 7.55 = 6.4175mm. In speaker 10, the distance L is set to be equal to or greater than the minimum value 2z. The value 2z of the distance between the first speaker element 51 and the second speaker element 52 with a mid-frequency fmid of 135kHz is 2z = C(y) × λmid = 0.85 × 2.52 = 2.142mm. The rounded values ​​are shown in the figure.

[0072] like Figure 8 and Figure 9 As shown, the coefficient C(y) is a constant value and is independent of the frequency f. At the minimum distance y = 100 mm, the coefficient C(y) is 0.85. Therefore, in this embodiment, the minimum value of the coefficient C(y) is 0.85. The distance L between the two speaker elements 51 and 52, which have two adjacent resonant frequencies f1 and f2, is set to be equal to or greater than the value obtained by multiplying the intermediate wavelength λmid by the coefficient C(y) = 0.85. As a result, even if the position of the object moves from the specified position, it is possible to reproduce sound pressure without troughs on the surface of the object. In other words, even if the position of the object moves from the specified position, it is possible to reproduce a broadband sound with approximately uniform sound pressure on the surface of the object. The distance L is set such that the sound in the broadband including the intermediate frequency fmid has uniform sound pressure at multiple locations on the surface of the object without including sound pressure troughs at the intermediate frequency fmid.

[0073] At the maximum distance y = 2000 mm, the coefficient C(y) is 13.71. In this embodiment, the maximum value of the coefficient C(y) is 13.71. The minimum value of the coefficient C(y) is the general minimum value of the ultrasonic system 1. The maximum value of the coefficient C(y) depends on the distance y. The maximum value of the coefficient C(y) can be set according to the value of the distance y. The maximum value of the coefficient C(y) is also limited by the maximum value of the distance L. The maximum value of the distance L can depend on the loudspeaker 10. When the loudspeaker 10 has a relatively large scale corresponding to the total width of the target space TR, the maximum value of the distance L can reach the maximum width WM of the target space TR in the width direction WD. Therefore, the maximum value of the distance L is equal to or less than the maximum width WM in the width direction WD of the target space TR. The distance L is set to be equal to or less than the width of the target space. Here, the width represents the length in the direction parallel to the central axis AXz. When the loudspeaker 10 is formed from a single semiconductor substrate 41, the maximum value of the distance L is equal to or less than the maximum value of the semiconductor chip or equal to or less than the maximum value of the semiconductor wafer.

[0074] According to the above embodiment, the distance L is set such that the sound from the first speaker element 51 and the sound from the second speaker element 52 have a predetermined relationship PS at the target position TG. The target position TG is two or more positions on an object located in the target space. The predetermined relationship is such that the sound from the first speaker element and the sound from the second speaker element reinforce each other at an intermediate frequency fmid between the first resonant frequency f1 and the second resonant frequency f2. In other words, the distance L is set such that the reinforcement relationship PS occurs at two or more positions TG on the object located in the target space. The sound from the first speaker element 51 with an intermediate frequency fmid and the sound from the second speaker element 52 with an intermediate frequency fmid reinforce each other with the reinforcement relationship PS. The intermediate frequency fmid is the intermediate frequency between the first resonant frequency f1 and the second resonant frequency f2. As a result, the reinforcement relationship of the sound with the intermediate frequency fmid can be provided at two or more positions on the object. As a result, an ultrasonic generator that provides strong sound pressure in a wide frequency band can be provided. Furthermore, even if the position of the object moves, strong sound pressure can still be provided to the object.

[0075] The distance L is set to be equal to or greater than the value 2z obtained by multiplying the coefficient C(y) = 0.85 by the intermediate wavelength λmid of the speaker elements 51 and 52 having adjacent resonant frequencies f1 and f2. As a result, even if the face moves the same width as the face from a specified position in the width direction WD, a sound without dips close to the intermediate frequency fmid can be provided on the surface of the face. By appropriately setting the distance L, the desired effect can be obtained through the miniature speaker 10.

[0076] The teachings of this disclosure are not limited to embodiments targeting a human face. In this embodiment, assuming a human face, the value of distance x is set to 73 mm. Those skilled in the art who understand this disclosure will appreciate that the value of distance x can be set depending on the object. For example, in an ultrasound system 1 targeting the upper body of a person, distance x can be set to a value exceeding 100 mm. Furthermore, when the entire human body, with its central axis AXz aligned with the direction of gravity and in a standing posture, is the target, distance x can be set in the range of 1000 mm to 2000 mm. This disclosure should be construed as including these variations.

[0077] Second Embodiment

[0078] This embodiment is a modification based on the foregoing embodiment. In the above embodiment, a speaker pair 60, consisting of two speaker elements 51 and 52 having adjacent resonant frequencies, is formed on a semiconductor substrate 41. Optionally, in this embodiment, multiple speaker pairs 60, including two speaker elements having adjacent resonant frequencies, are formed in a distributed manner on different semiconductor substrates 242 and 243 arranged separately from each other.

[0079] exist Figure 10 In the ultrasonic system 1, a loudspeaker 10 is included. The loudspeaker 10 includes a first loudspeaker 211 and a second loudspeaker 212. The first loudspeaker 211 and the second loudspeaker 212 can be replaced by the first loudspeaker 11 and the second loudspeaker 12 in the first embodiment. The dimensions of the first loudspeaker 211 and the second loudspeaker 212 in the width direction WD are larger than those of the first loudspeaker 11 and the second loudspeaker 12 in the first embodiment. The dimensions of the first loudspeaker 211 and the second loudspeaker 212 in the width direction WD are equal to or less than the maximum width WM.

[0080] exist Figure 11In this design, a loudspeaker 10 has a housing 30. The loudspeaker 10 includes a plurality of semiconductor elements 40 disposed within the housing 30. The plurality of semiconductor elements 40 are provided by a plurality of semiconductor substrates 242 and 243. The loudspeaker 10 includes a first semiconductor substrate 242 and a second semiconductor substrate 243 disposed separately from each other. Semiconductor substrates 242 and 243 belong to a loudspeaker 10 oriented toward a target region TR. The loudspeaker 10 includes a plurality of loudspeaker elements 50. The plurality of loudspeaker elements 50 are distributed on semiconductor substrates 242 and 243. A first loudspeaker element is formed on the first semiconductor substrate 242, and a second loudspeaker element is formed on the second semiconductor substrate 243.

[0081] In this embodiment, multiple speaker pairs 60 are distributed on semiconductor substrates 242 and 243. For example, a speaker element 51 having a resonant frequency f1 = 40 kHz and a speaker element 52 having a resonant frequency f2 = 50 kHz form one speaker pair 60. Furthermore, a speaker element 52 having a resonant frequency f1 = 50 kHz and a speaker element 53 having a resonant frequency f2 = 60 kHz form another speaker pair 60. The speaker 10 emits sound with a wide frequency band from 40 kHz to 140 kHz. The speaker 10 includes multiple speaker elements 50 having different resonant frequencies, each spaced 10 kHz apart. The speaker 10 includes 10 speaker pairs 60.

[0082] The central axes of the multiple speaker pairs 60 can be slightly tilted relative to the central axis AXz. For example, the speaker pairs 60 including speaker elements 51 and 52 are separated by a distance L1 on the central axis AX4050. The speaker pairs 60 including speaker elements 52 and 53 are separated by a distance L2 on the central axis AX5060. Therefore, the multiple speaker pairs 61 and 62 have different central axes AX4050 and AX5060 that intersect each other. However, since the semiconductor substrates 242 and 243 are small, the central axes AX of the multiple speaker pairs 60 can be considered to be substantially parallel to each other. The multiple central axes including the central axes AX4050 and AX5060 can be considered to be substantially parallel to the central axis AXz.

[0083] First loudspeaker element 51 and second loudspeaker element 52 are separated by a distance L1 along the central axis AXz. First loudspeaker element 51 and second loudspeaker element 52 form a first loudspeaker pair 61. The first loudspeaker pair 61 is characterized by a first intermediate frequency fmid1 = 45 kHz. Second loudspeaker element 52 and third loudspeaker element 53 are separated by a distance L2 along the central axis AXz. Second loudspeaker element 52 and third loudspeaker element 53 form a second loudspeaker pair 62. The second loudspeaker pair 62 is characterized by a second intermediate frequency fmid2 = 55 kHz. Similarly, 10 pairs of loudspeaker pairs 60 are formed. All loudspeaker pairs 60 are characterized by their respective intermediate frequencies fmid. The distance L (L1, L2...) between all loudspeaker pairs 60 is equal to or greater than the value 2z given by equation (9) or equation (11) above.

[0084] The distance L1 between speaker element 51 and speaker element 52 is equal to or greater than a value 2z that can be set according to the intermediate frequency fmid = 45 kHz. The distance L2 between speaker element 52 and speaker element 53 is equal to or greater than a value 2z that can be set according to the intermediate frequency fmid = 55 kHz. Similarly, the distance between all speaker elements 50 is equal to or greater than a value 2z that can be set according to the intermediate frequency fmid. All distances L1, L2... are set such that the sound at the intermediate frequency is observed in an enhanced manner on the surface of the object located in the target space TR without causing a trough.

[0085] The resonant frequency of speaker element 51 is close to, but not adjacent to, the resonant frequency of speaker element 53. The sound at the mid-frequency between the resonant frequency of speaker element 51 and the resonant frequency of speaker element 52 has a small sound pressure level, which is negligible. In this specification, the term "pair" or "speaker pair" refers to a pair of speaker elements in speaker 10 that have adjacent resonant frequencies.

[0086] Third Embodiment

[0087] This embodiment is a modification based on the foregoing embodiment. In the foregoing embodiment, a speaker pair 60, comprising two speaker elements 51 and 52 having adjacent resonant frequencies, is arranged in a container 30. Optionally, in this embodiment, multiple speaker pairs 60, comprising two speaker elements having adjacent resonant frequencies, are distributed in different containers 31 and 32 arranged separately from each other.

[0088] exist Figure 12In this ultrasonic system 1, a loudspeaker 10 is included. The loudspeaker 10 includes a first loudspeaker 11, a second loudspeaker 312, and a third loudspeaker 313. The first loudspeaker 11 can be described in the foregoing embodiments. The sound wave direction TD2 of the second loudspeaker 312 points towards a target space TR2 corresponding to the rear seat space. The sound wave direction TD3 of the third loudspeaker 313 points towards the target space TR2 corresponding to the rear seat space. The second loudspeaker 312 and the third loudspeaker 313 together provide a single loudspeaker. The second loudspeaker 312 and the third loudspeaker 313 provide the function corresponding to the second loudspeaker 12 in the foregoing embodiments.

[0089] Figure 13 A plurality of loudspeakers 312 and 313 are shown providing a loudspeaker 10. In this embodiment, two of the loudspeakers in the first loudspeaker 312 and the second loudspeaker 313 provide one loudspeaker in the loudspeaker 10. The second loudspeaker 312 includes a container 31 and a semiconductor substrate 344 disposed in the container 31. The second loudspeaker 312 has a plurality of loudspeaker elements. The third loudspeaker 313 includes a container 32 and a semiconductor substrate 345 disposed in the container 32. The third loudspeaker 313 has a plurality of loudspeaker elements. The plurality of semiconductor substrates 344 and 345 are distributed in the plurality of containers 31 and 32. Also in this embodiment, the loudspeaker 10 includes a first semiconductor substrate 344 and a second semiconductor substrate 345 disposed separately from each other. The first loudspeaker element is formed on the first semiconductor substrate 344, and the second loudspeaker element is formed on the second semiconductor substrate 345.

[0090] A speaker element belonging to the second speaker 312 and a speaker element belonging to the third speaker 313 provide two speaker elements having adjacent resonant frequencies. Multiple speaker elements belonging to the second speaker 312 and multiple speaker elements belonging to the third speaker 313 form multiple speaker pairs 60. In this embodiment, all speaker elements 50 form multiple speaker pairs 60.

[0091] First speaker element 51 and second speaker element 52 are separated by a distance L1 along the central axis AXz. First speaker element 51 and second speaker element 52 form a first speaker pair 61. The first speaker pair 61 is characterized by a first intermediate frequency fmid1 = 45 kHz. Second speaker element 52 and third speaker element 53 are separated by a distance L2 along the central axis AXz. Second speaker element 52 and third speaker element 53 form a second speaker pair 62. The second speaker pair 62 is characterized by a second intermediate frequency fmid2 = 55 kHz. Similarly, 10 pairs of speaker pairs 60 are formed. All speaker pairs 60 are characterized by their respective intermediate frequencies fmid. The distance L (L1, L2...) between all speaker pairs 60 is equal to or greater than the value 2z given by equation (9) or equation (11) above. Also in this embodiment, the plurality of speaker pairs 61 and 62 have different central axes that intersect each other.

[0092] In the illustrated example, loudspeaker 10 includes a plurality of loudspeaker elements 50. The plurality of loudspeaker elements 50 are distributed on semiconductor substrates 344 and 345. The 10 loudspeaker elements form 10 pairs of loudspeakers 60. As in the previous embodiments, the distance L between each pair of loudspeakers 60 is set to be equal to or greater than a minimum value 2z, and is set to be equal to or less than a maximum value. Therefore, even in this embodiment, it is possible to provide uniform sound pressure without valleys over a wide frequency band on the surface of an object located in the target space TR.

[0093] As clearly described from the disclosure of the first, second, and third embodiments, a plurality of speaker elements 50 are arranged to form a plurality of speaker pairs 60. The plurality of speaker elements 50 may be arranged in a distributed manner within a container 30 forming a speaker 10. Optionally, the plurality of speaker elements 50 may be distributed within a plurality of containers 30 forming a speaker 10. Optionally, the plurality of speaker elements 50 may be arranged in a distributed manner within a semiconductor element 40 forming a speaker 10. Optionally, the plurality of speaker elements 50 may be distributed within a plurality of semiconductor elements 40 forming a speaker 10. In the following description, the arrangement of the plurality of speaker elements 50 is described without being limited to the container 30 and the semiconductor element 40.

[0094] Fourth embodiment

[0095] This embodiment is a modification based on the foregoing embodiment. In the foregoing embodiment, the directions of the plurality of speaker elements 50 included in a speaker 10 are substantially parallel to each other at a distance L. On the other hand, in this embodiment, a speaker 10 includes a plurality of speaker elements 50 that are substantially intersecting each other at a distance L.

[0096] exist Figure 14In the diagram, loudspeaker 10 includes multiple loudspeaker elements 50. A typical loudspeaker element 50 is illustrated in the figure. Loudspeaker 10 includes four loudspeaker elements 51, 52, 451, and 452. The multiple loudspeaker elements 50 are arranged at the intersections of a matrix. The multiple loudspeaker elements 50 are arranged in the matrix.

[0097] The loudspeaker 10 includes a first loudspeaker element 51 and a second loudspeaker element 52. The first loudspeaker element 51 has a resonant frequency f1. The second loudspeaker element 52 has a resonant frequency f2. The first loudspeaker element 51 and the second loudspeaker element 52 form a first loudspeaker pair 461. The first loudspeaker element 51 and the second loudspeaker element 52 belonging to the first loudspeaker pair 461 are separated by a distance L1 on a central axis AXz1. The central axis AXz1 extends horizontally. The distance L1 is equal to or greater than the value 2z.

[0098] Loudspeaker 10 includes a third loudspeaker element 451 and a fourth loudspeaker element 452. The third loudspeaker element 451 has a resonant frequency f1. The fourth loudspeaker element 452 has a resonant frequency f2. The third loudspeaker element 451 and the fourth loudspeaker element 452 form another second loudspeaker pair 462. The third loudspeaker element 451 and the fourth loudspeaker element 452, belonging to the second loudspeaker pair 462, are separated by a distance L1 on a central axis AXz2. The central axis AXz2 extends along the direction of gravity (vertical direction). The distance L1 is equal to or greater than the value 2z.

[0099] Central axes AXz1 and AXz2 intersect at a common point. They are orthogonal to each other at the common point.

[0100] Loudspeaker 10 forms a third loudspeaker pair 463 consisting of a first loudspeaker element 51 and a fourth loudspeaker element 452. The first loudspeaker element 51 and the fourth loudspeaker element 452 belonging to the third loudspeaker pair 463 are separated by a distance L2 on the central axis AXz3. The central axis AXz3 extends in a skewed direction relative to the direction of gravity. The distance L2 is equal to or greater than the value 2z.

[0101] Loudspeaker 10 forms a fourth loudspeaker pair 464, consisting of a third loudspeaker element 451 and a second loudspeaker element 52. The third loudspeaker element 451 and the second loudspeaker element 52, belonging to the fourth loudspeaker pair 464, are separated by a distance L2 on a central axis AXz4. The central axis AXz4 extends in a skewed direction relative to the direction of gravity. The central axes AXz3 and AXz4 are parallel to each other. The distance L2 is equal to or greater than the value 2z.

[0102] The first speaker pair 461 and the second speaker pair 462 are referred to as the primary speaker pair. The third speaker pair 463 and the fourth speaker pair 464 are referred to as secondary speaker pairs collaterally formed by the first speaker pair 461 and the second speaker pair 462. It should be understood that these primary and secondary designations are subjective and can be used interchangeably. Also in this embodiment, the multiple speaker pairs 461, 462, 463 and 464 have different central axes AXz1, AXz2, AXz3 and AXz4 that intersect each other.

[0103] In this embodiment, the first speaker pair 461 and the second speaker pair 462 have the same frequencies characterizing their features. The frequencies characterizing the first speaker pair 461 and the second speaker pair 462 are the resonant frequency f1, the resonant frequency f2, and the intermediate frequency fmid. In other words, the first speaker pair 461 and the second speaker pair 462 completely overlap with respect to the frequencies characterizing their features. Alternatively, the first speaker pair 461 and the second speaker pair 462 at least partially overlap with respect to the frequencies characterizing their features.

[0104] The first speaker pair 461 and the second speaker pair 462 are positioned where the central axes AXz1 and AXz2 intersect. The central axes AXz1 and AXz2 may intersect in space. The central axes AXz1 and AXz2 do not necessarily intersect at the common point shown in the illustrated example. For example, the first speaker pair 461 and the second speaker pair 462 may be separate from each other.

[0105] Figure 15 Multiple relationship lines PL1, PL2, and PL3 provided by multiple loudspeaker pairs 461, 462, 463, and 464 are shown. Relationship lines PL1, PL2, and PL3 indicate the locations where reinforcement relationships are obtained for sound with an intermediate wavelength λmid. The first loudspeaker pair 461 provides relationship line PL1. The second loudspeaker pair 462 provides relationship line PL2. The third loudspeaker pair 463 provides relationship line PL3. The fourth loudspeaker pair 464 provides relationship line PL3. Relationship lines PL1, PL2, and PL3 are portions of a curve.

[0106] The intersection angle between relation lines PL1 and PL2 is equal to the intersection angle between the central axis AXz1 of the first speaker pair 461 and the central axis AXz2 of the second speaker pair 462. In this embodiment, the intersection angle is 90 degrees.

[0107] Furthermore, relationship line PL3 intersects with relationship lines PL1 and PL2. The angles of intersection between relationship lines PL1 and PL2 and relationship line PL3 are equal to the angles of intersection between central axes AXz1 and AXz2 and central axes AXz3 and AXz4. In this embodiment, the angles are +45 degrees and -45 degrees.

[0108] According to this embodiment, uniform sound pressure levels near the mid-frequency fmid can be obtained at multiple laterally separated locations in the target space. Additionally, uniform sound pressure levels near the mid-frequency fmid can be obtained at multiple vertically separated locations in the target space. By intersecting the central axes of multiple speaker pairs 461 and 462, auxiliary speaker pairs 463 and 464 are created. As a result, uniform sound pressure levels near the mid-frequency fmid can be further obtained at multiple diagonally separated locations in the target space. In this embodiment, high sound pressure levels can be provided at many locations. Furthermore, high sound pressure levels can be provided even when the object moves in the horizontal direction SH1 and the vertical direction SH2. Moreover, by providing the relationship line PL3, high sound pressure levels can be provided even when the object moves in the oblique direction SH3.

[0109] Fifth Embodiment

[0110] This embodiment is a modification based on the foregoing embodiment. In the foregoing embodiment, the intersection angle of the central axes of the plurality of speaker pairs included in a speaker 10 is 90 degrees. Optionally, the intersection angle of the plurality of central axes can be set to an angle other than 90 degrees.

[0111] exist Figure 16 In this design, the loudspeaker 10 includes a plurality of loudspeaker elements 50. The plurality of loudspeaker elements 50 form a plurality of loudspeaker pairs 60. For example, loudspeaker element 51 and loudspeaker element 52 form one loudspeaker pair. Loudspeaker element 551 and loudspeaker element 552 together form one loudspeaker pair. Loudspeaker element 52 and loudspeaker element 551 form an affiliated loudspeaker pair. Furthermore, loudspeaker element 51 and loudspeaker element 552 form an affiliated loudspeaker pair.

[0112] These multiple speaker pairs form multiple groups. These multiple groups can be distinguished by their angle about the central axis AXz. In this embodiment, two primary groups 561 and 562 are formed. Furthermore, in this embodiment, two secondary groups 563 and 564 are formed. Each group has an element corresponding to one speaker 10. The first group 561, which includes multiple speaker pairs, has a central axis AXz1. The second group 562, which includes multiple speaker pairs, has a central axis AXz2. The third group 563, which includes multiple speaker pairs, has a central axis AXz3. The fourth group 564, which includes multiple speaker pairs, has a central axis AXz4.

[0113] The first group 561 and the second group 562 are arranged in a line-symmetrical manner with respect to the horizontal central axis. The arrangement of the first group 561 and the arrangement of the second group 562 are similar. The central axis AXz1 of the first group 561 and the central axis AXz2 of the second group 562 intersect at an angle different from 90 degrees. The central axis AXz1 extends obliquely with respect to the direction of gravity. The central axis AXz2 extends obliquely with respect to the direction of gravity. These oblique angles are different from 90 degrees. The central axis AXz1 and the central axis AZx2 are inclined in a direction opposite to the direction of gravity. The central axis AXZ3 of the third group 563 also intersects the central axes AXz1 and AXz2 at an angle different from 90 degrees. The central axis AXZ4 of the fourth group 564 also intersects the central axes AXz1 and AXz2 at an angle different from 90 degrees. The central axis AXZ3 and the central axis AXz4 are parallel to each other. The central axes AXz3 and AXz4 extend in the horizontal direction. Also in this embodiment, the plurality of speaker pairs 561, 562, 563, 564 have different central axes AXz1, AXz2, AXz3, and AXz4 that intersect each other.

[0114] Also in this embodiment, the distances between the components satisfy the conditions described in the foregoing embodiments. Also in this embodiment, the same effects as those in the foregoing embodiments can be obtained. Additionally, in this embodiment, a high sound pressure with an intermediate frequency fmid can be obtained at a large number of positions in the target space TR in the directions corresponding to the central axes AXz1 and AXz2. <()

[0115] Sixth Embodiment

[0116] This embodiment is a modification based on the foregoing embodiments. In the foregoing embodiments, the plurality of speaker elements 50 included in one speaker are irregularly arranged. Alternatively, in this embodiment, the second speaker pair is arranged inside (internally) the first speaker pair. In other words, the first speaker pair is arranged outside (externally) the second speaker pair. The first speaker pair is characterized by a first intermediate frequency fmid1. The second speaker pair is characterized by a second intermediate frequency fmid2. The second intermediate frequency fmid2 is higher than the first intermediate frequency fmid1 (fmid1 < fmid2). The relationship between the plurality of speaker pairs in this embodiment is also referred to as an internal / external position relationship in the following description.

[0117] In Figure 17In this embodiment, the loudspeaker 10 covers a predetermined wide bandwidth (approximately 40 kHz to approximately 140 kHz). The loudspeaker 10 includes a plurality of loudspeaker elements 50. The plurality of loudspeaker elements 50 have different resonant frequencies from each other. The resonant frequencies of the plurality of loudspeaker elements 50 are different for each predetermined frequency difference. The plurality of loudspeaker elements 50 form a plurality of loudspeaker pairs 60. In this embodiment, the loudspeaker 10 includes 10 loudspeaker elements 50. The 10 loudspeaker elements form 10 pairs of loudspeakers 60. Each of the plurality of loudspeaker elements 50 has a resonant frequency of 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, or 140 kHz. The frequency difference is 10 kHz. The frequency difference and number of the plurality of loudspeaker elements 50 are not limited to the illustrated embodiment. For example, the frequency difference can be various frequency differences, such as 5 kHz and 20 kHz. For example, the loudspeaker 10 can include several to a dozen or more loudspeaker elements 50. The plurality of loudspeaker elements 50 can be centrally formed on a single semiconductor substrate or can be distributed on multiple semiconductor substrates.

[0118] The first loudspeaker element 51 and the second loudspeaker element 52 are separated by a distance L1 along the central axis AXz. The first loudspeaker element 51 and the second loudspeaker element 52 form a first loudspeaker pair 661. The first loudspeaker pair is characterized by a first intermediate frequency fmid1 = 45 kHz.

[0119] The second loudspeaker element 52 and the third loudspeaker element 53 are separated by a distance L2 along the central axis AXz. The second loudspeaker element 52 and the third loudspeaker element 53 form a second loudspeaker pair 662. The second loudspeaker pair 662 is characterized by a second intermediate frequency fmid2 = 55kHz.

[0120] The first intermediate frequency fmid1 is lower than the second intermediate frequency fmid2. Distances L1 and L2 are equal to or greater than the theoretical set value 2z. Distance L1 is greater than distance L2. The second loudspeaker pair 662 is arranged inside the first loudspeaker pair 661.

[0121] In this embodiment, all speaker pairs in the loudspeaker 10 satisfy an internal / external positional relationship. Optionally, a portion of the speaker pairs, or two speaker pairs, may satisfy the aforementioned internal / external positional relationship among multiple speaker pairs in the loudspeaker 10. In one example, the first intermediate frequency of the first speaker pair arranged externally and the second intermediate frequency of the second speaker pair arranged internally in the first speaker pair may be greater than the aforementioned frequency difference. In another example, at least two speaker pairs belonging to the low-frequency side may satisfy the aforementioned internal / external positional relationship, and multiple speaker pairs on the high-frequency side may be arranged irregularly. Conversely, at least two speaker pairs belonging to the high-frequency side may satisfy the aforementioned internal / external positional relationship, and multiple speaker pairs on the low-frequency side may be arranged irregularly.

[0122] The internal / external positional relationship of this embodiment can be combined with the features of the foregoing embodiments. For example, Figure 16 The plurality of speaker elements 50 shown can be arranged to satisfy Figure 17 The internal / external positional relationship is shown.

[0123] Other embodiments

[0124] The disclosure in this specification, drawings, etc., is not limited to exemplary embodiments. This disclosure includes illustrated embodiments and modifications made thereto by those skilled in the art. For example, this disclosure is not limited to combinations of components and / or elements shown in the embodiments. This disclosure can be implemented in various combinations. This disclosure may have additional components that can be added to the embodiments. This disclosure includes embodiments in which some components and / or elements are omitted. This disclosure covers substitutions or combinations of components and / or elements between one embodiment and another. The scope of the disclosed technology is not limited to the description of the embodiments. Several technical scopes disclosed are indicated by the description in the claims and should be understood to include all modifications within the meaning and scope equivalent to the description in the claims.

[0125] The disclosures in the specification, drawings, etc., are not limited to the descriptions in the claims. The disclosures in the specification, drawings, etc., include the technical ideas described in the claims, and further extend to technical ideas that are broader than those in the claims. Therefore, various technical ideas can be extracted from the disclosures in the specification, drawings, etc., without being bound by the descriptions in the claims.

Claims

1. An ultrasonic sound generator that emits sound waves toward a target space, comprising: a plurality of speaker elements that are piezoelectric MEMS ultrasonic transducers, wherein the plurality of speaker elements comprises: a first speaker element having a first resonant frequency; and a second speaker element having a second resonant frequency adjacent to the first resonant frequency, wherein the first speaker element and the second speaker element are arranged apart from each other in a direction intersecting a direction toward the target space, and wherein a distance between the first speaker element and the second speaker element is set so that a reinforcing relationship of sound having an intermediate frequency from the first speaker element and from the second speaker element occurs at two or more locations on an object located in the target space, and wherein the reinforcing relationship is created by reinforcing sound having the intermediate frequency between the first resonant frequency and the second resonant frequency from the first speaker element and sound having the intermediate frequency from the second speaker element. wherein the distance is set to a value equal to or greater than 2z obtained from the equation n=(SQRT((z+x) 2 +y 2 )-SQRT((z-x) 2 +y 2 )) / λmid+1 / 2) where n is a natural number equal to or greater than 1, z is a distance between a midpoint of two speaker elements and one of the speaker elements, x is a width of the object, y is a distance between the midpoint and the object, and λmid is a wavelength of the mid frequency.

2. The ultrasonic sound generator of claim 1, further comprising: a semiconductor substrate made of a continuous material, wherein both the first speaker element and the second speaker element are formed on the semiconductor substrate.

3. The ultrasonic sound generator of claim 1, further comprising: a first semiconductor substrate and a second semiconductor substrate arranged apart from each other, wherein the first speaker element is formed on the first semiconductor substrate and the second speaker element is formed on the second semiconductor substrate.

4. The ultrasonic sound generator of any one of claims 1-3, wherein the plurality of speaker elements forms a plurality of speaker pairs.

5. The ultrasonic sound generator of claim 4, wherein the plurality of speaker pairs have different central axes that intersect each other.

6. The ultrasonic sound generator of claim 4, wherein the plurality of speaker pairs comprises: a first speaker pair featuring a first intermediate frequency; and a second speaker pair featuring a second intermediate frequency higher than the first intermediate frequency, wherein the second speaker pair is arranged inside the first speaker pair.

7. The ultrasonic sound generator of any one of claims 1-3, wherein the first speaker element and the second speaker element are arranged sufficiently apart from each other with respect to a wavelength of the intermediate frequency.

8. The ultrasonic sound generator of any one of claims 1-3, wherein the distance is set to be equal to or greater than a value 2z obtained from Equation 2z = 0.85 x lmid, where the object is a human face, n is a natural number of 1 or more, and z is a distance between a midpoint between two speaker elements and one of the speaker elements.

9. The ultrasonic sound generator of claim 8, wherein the distance is set to be equal to or less than a width of the target space. ​

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