Ultrasonic generator and highly directional speaker

Abstract

The goal is to achieve both an expanded range of sound field formation and suppression of the decrease in directivity caused by variations in the resonant frequencies of sound sources within the MEMS array. [Solution] An ultrasonic generator that emits an ultrasonic beam, comprising a cantilever structure sound source created by a MEMS (Micro Electro Mechanical Systems) process, comprising a plurality of cantilever vibrators arranged in an array, and wiring connected to the plurality of cantilever vibrators so as to be able to supply electrical signals individually to each of the plurality of cantilever vibrators, wherein the plurality of cantilever vibrators emit ultrasonic waves that form the ultrasonic beam in response to the supply of the electrical signals.

Description

[Technical Field]

[0001] This invention relates to an ultrasonic generator and a highly directional speaker. [Background technology]

[0002] Conventionally, parametric speakers (highly directional speakers) that generate audible sound only in a narrow area along a highly directional ultrasonic beam have been known as ultrasonic generators.

[0003] Patent Document 1 discloses a parametric speaker that has multiple oscillators that emit ultrasonic waves arranged in an array, and can form sound fields in multiple regions by controlling the phase of the ultrasonic waves output from each oscillator.

[0004] Furthermore, Patent Document 2 discloses a configuration in which a MEMS (Micro Electro Mechanical Systems) array is used as a super-directional speaker. [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in conventional structures using a diaphragm fixed to the outer perimeter as a resonator, residual stress during MEMS chip manufacturing and thermal stress during MEMS chip mounting cause variations in the resonant frequencies of each sound source element within the MEMS array. This leads to problems such as a decrease in the intensity of the ultrasonic beam or a widening of the ultrasonic beam, resulting in reduced directivity.

[0006] The present invention has been made in view of the above, and aims to achieve both an expansion of the range in which a sound field can be formed and a suppression of the decrease in directivity due to variations in the resonant frequencies of sound sources within the MEMS array. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the present invention provides an ultrasonic generator for emitting an ultrasonic beam, which is a cantilever structure sound source created by a MEMS (Micro Electro Mechanical Systems) process, comprising: a plurality of cantilever vibrators arranged in an array; and wiring connected to the plurality of cantilever vibrators so as to be able to supply electrical signals individually to each of the plurality of cantilever vibrators, wherein the plurality of cantilever vibrators emit ultrasonic waves that form the ultrasonic beam in response to the supply of the electrical signals. [Effects of the Invention]

[0008] According to the present invention, it is possible to achieve both an expansion of the range in which a sound field can be formed and a suppression of the decrease in directivity due to variations in the resonant frequencies of sound sources within the MEMS array. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows the configuration of a parametric speaker according to the first embodiment. [Figure 2] Figure 2 shows the maximum angle at which an ultrasonic beam can be bent. [Figure 3] Figure 3 shows the configuration of an ultrasonic array sound source. [Figure 4] Figure 4 is a schematic plan view showing the structure of an ultrasonic actuator. [Figure 5] Figure 5 is a schematic cross-sectional view showing the structure of an ultrasonic actuator. [Figure 6] Figure 6 shows an example of an array arrangement of ultrasonic actuators. [Figure 7] Figure 7 shows the relationship between the voltage applied to the actuator and the generated sound pressure. [Figure 8] Figure 8 shows the configuration of an ultrasonic array sound source according to the second embodiment. [Figure 9] Figure 9 shows a modified example of wiring to an array of ultrasonic actuators. [Figure 10] FIG. 10 is a plan view schematically showing the structure of the ultrasonic actuator in the actuator unit according to the third embodiment. [Figure 11] FIG. 11 is a diagram showing the configuration of the ultrasonic array sound source according to the fourth embodiment. [Figure 12] FIG. 12 is a schematic diagram showing an example of the configuration of the digital signage according to the fifth embodiment. [Figure 13] FIG. 13 is a schematic diagram showing an example of the configuration of the caution device according to the sixth embodiment. [Figure 14] FIG. 14 is a schematic diagram showing an example of the configuration of the simultaneous interpretation device according to the seventh embodiment. [Figure 15] FIG. 15 is a schematic diagram showing an example of the configuration of the directional sound source according to the eighth embodiment. [Figure 16] FIG. 16 is a schematic diagram showing an example of the configuration of the notebook personal computer according to the ninth embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0013] The control unit 50 can control the directivity of the ultrasonic array sound source 10 so that, for example, different sounds are reproduced in multiple sound fields.

[0014] Here, we will explain the problems with conventional parametric speakers.

[0015] In parametric speakers, the direction of the ultrasonic beam's emission can be controlled by appropriately changing the phase of the ultrasonic waves generated from the source elements within the ultrasonic array sound source.

[0016] However, the maximum angle at which the ultrasonic beam can be bent is limited by the following constraints based on the distance between sound sources and the ultrasonic wavelength.

[0017] Here, Figure 2 shows the maximum angle at which an ultrasonic beam can be bent. In Figure 2, for simplicity, we consider the case where the phase of ultrasonic waves emitted from a one-dimensional array sound source arranged at intervals d in one dimension along the x-axis is controlled, and the ultrasonic beam is emitted in a direction tilted at an angle θ from the y-axis. In the example shown in Figure 2, the limiting angle θ that can be bent is given by equation (1) below. st That will be decided. θ st =Sin -1 (λ / d-1) ... Equation (1) Here, each symbol in equation (1) means the following: Sin -1 (·): Arcsine function λ: Ultrasonic wavelength

[0018] θ>θ stWhen phase control is used to direct an ultrasonic beam, a beam called a grating lobe is generated in an undesirable direction, causing sound leakage from the parametric speaker. That is, θ st To increase the volume, the interval between sound sources needs to be reduced.

[0019] Conventional parametric speakers often use an array of commercially available ultrasonic sound sources, but this configuration makes it difficult to reduce the spacing between each sound source. As a result, the sound source spacing d in equation (1) cannot be reduced, and the limit angle of bending cannot be increased.

[0020] Furthermore, the directivity of an ultrasonic beam depends on the dimensions of the speaker and the frequency of the ultrasound. Even when creating a beam with the same directivity, using higher frequency ultrasound allows for a smaller speaker. Therefore, using higher frequency ultrasound is advantageous from the standpoint of miniaturizing the speaker itself. However, increasing the frequency of ultrasound reduces the ultrasonic wavelength λ in equation (1), which further tightens the requirement for reducing the sound source spacing d.

[0021] To reduce the sound source spacing d, it is effective to create ultrasonic sound sources using MEMS (Micro Electro Mechanical Systems) and use an array of these high-density sources as the sound source for a parametric speaker, as described in Japanese Patent Publication No. 2008-020429. This configuration allows for a smaller sound source spacing d, enabling the emission of an ultrasonic beam over a wide angular range. Furthermore, this configuration makes it easy to generate higher frequency ultrasonic waves and allows for a smaller speaker. However, in the structure described in Japanese Patent Publication No. 2008-020429, where the diaphragm is fixed to the outer periphery as the resonator, residual stress during MEMS chip manufacturing and thermal stress during MEMS chip mounting cause variations in the resonant frequency of the sound sources within the MEMS array, leading to problems such as reduced ultrasonic beam intensity and beam spreading, resulting in reduced directivity.

[0022] Therefore, the parametric speaker 100 of this embodiment is designed to achieve both an expansion of the range over which a sound field can be formed and a suppression of the decrease in directivity due to variations in the resonant frequencies of sound sources within the MEMS array. This will be described in detail below.

[0023] First, the configuration of the ultrasonic array sound source 10 of the parametric speaker 100 in this embodiment will be described.

[0024] Figure 3 shows the configuration of the ultrasonic array sound source 10. As shown in Figure 3, the ultrasonic array sound source 10 of the parametric speaker 100 is composed of an array of ultrasonic actuators 11. More specifically, the ultrasonic array sound source 10 is composed of a MEMS array in which ultrasonic actuators 11, which are MEMS chips, are arranged at high density. Wiring 13 for supplying electrical signals independently is drawn from each ultrasonic actuator 11 that makes up the ultrasonic array sound source 10. That is, the wiring 13 is connected in such a way that individual electrical signals can be supplied to multiple ultrasonic actuators 11. The wiring 13 drawn from each ultrasonic actuator 11 is connected to individual connection terminals 14.

[0025] Next, the structure of the ultrasonic actuator 11 will be described.

[0026] Figure 4 is a schematic plan view showing the structure of the ultrasonic actuator 11. Note that in Figure 4, for illustrative purposes, only the important functional parts are shown, and protective layers and other components present in the actual structure are omitted. Figure 5 is a schematic cross-sectional view showing the structure of the ultrasonic actuator 11. Figure 5 shows a cross-sectional view along the line connecting AA' in the plan view of Figure 4.

[0027] As shown in Figures 4 and 5, the ultrasonic actuator 11 is a MEMS chip created using a semiconductor process called MEMS (Micro Electro Mechanical Systems).

[0028] The ultrasonic actuator 11 is formed integrally by creating a piezoelectric layer 17, an upper electrode 18, a lower electrode 19, lower electrode wiring 20, upper electrode wiring 21, etc., on an SOI (Silicon On Insulator) substrate. The SOI substrate is a substrate in which a second silicon layer made of single-crystal silicon (Si) is provided on top of a first silicon layer made of single-crystal silicon (Si). Hereafter, the support layer 22 will be referred to as the first silicon layer, and the diaphragm portion 15 and the diaphragm support portion 24 will be referred to as the second silicon layer.

[0029] The diaphragm portion 15 and the diaphragm support portion 24 are supported by the support layer 22. Below the diaphragm portion 15, which is surrounded by the support layer 22, a cavity 23 is formed.

[0030] The diaphragm portion 15 has a smaller thickness in the z direction compared to the x or y direction as shown in Figures 4 and 5, thus providing elasticity as a diaphragm. The diaphragm portion 15 is a cantilever beam structure in which one side is a fixed end 25 fixed to the diaphragm support portion 24, and the other side is a free end separated from the diaphragm support portion 24 by a slit portion 16 which is a gap. In other words, the ultrasonic actuator 11 is a cantilever beam vibrator. The diaphragm portion 15 has a rectangular shape in which the y direction is longer than the x direction, as shown in Figure 4.

[0031] The diaphragm portion 15 is provided with a rectangular piezoelectric layer 17 on the fixed end 25 of the diaphragm portion 15. The piezoelectric layer 17 is sandwiched between an upper electrode 18 located at the top and a lower electrode 19 located at the bottom. The upper electrode 18 is electrically connected to an upper electrode wiring 21, which is an example of wiring 13. The lower electrode 19 is electrically connected to a lower electrode wiring 20, which is an example of wiring 13.

[0032] Next, the dimensions of each part of the ultrasonic actuator 11 will be described.

[0033] The thickness of the diaphragm portion 15 is typically 10 μm to 20 μm. The thickness of the piezoelectric layer 17 is 2 μm. The diaphragm portion 15 has a rectangular shape, with a short side length of 300 μm to 450 μm and a long side length of 800 μm to 1200 μm, and a long side / short side ratio of 2.4 to 2.8.

[0034] The piezoelectric layer 17 is formed on the diaphragm portion 15 and covers 50-80% of the diaphragm portion 15 on the cavity 23. The amount of the piezoelectric layer 17 overhanging toward the support layer 22 is approximately 20 μm.

[0035] The width of the slit portion 16 is typically 10 μm to 30 μm.

[0036] As will be described later, the dimensions of each part of the ultrasonic actuator 11 are appropriately changed according to the frequency of the ultrasound generated from the ultrasonic array sound source 10.

[0037] Next, we will describe the constituent materials of each part of the ultrasonic actuator 11.

[0038] The diaphragm portion 15 and the diaphragm support portion 24 are made of single-crystal silicon (Si) as described above. The support layer 22 is also made of single-crystal silicon (Si) as described above.

[0039] The piezoelectric layer 17 is composed of a piezoelectric material. The piezoelectric material is, for example, lead zirconate titanate (PZT).

[0040] The upper electrode 18 and the lower electrode 19 are typically composed of one or more layers of conductive material. The upper electrode 18 and the lower electrode 19 are conductive layers containing, for example, Ir.

[0041] The upper electrode wiring 21 and the lower electrode wiring 20 are made of a conductive material. The conductive material is, for example, Al-Cu.

[0042] The resonance frequency of the ultrasonic actuator 11 depends on parameters such as the shape, thickness, dimensions, and material rigidity of each part of the ultrasonic actuator 11. Therefore, the above parameters are designed according to the required resonance frequency of the ultrasonic wave.

[0043] In the case of the cantilever beam structure like the ultrasonic actuator 11 of this embodiment, it can be approximated and considered as a simple cantilever beam structure ignoring the layers other than single crystal silicon (Si). The resonance frequency f0 of the fundamental vibration mode of a homogeneous and isotropic cantilever beam follows the following theoretical formula (2).

[0044]

Equation

[0045] Here, each symbol in Equation (2) means the following. l: Length of the cantilever beam [m] h: Thickness of the cantilever beam [m] b: Depth of the cantilever beam [m] E: Young's modulus [Pa] I = bh 3 [[ / 12: Second moment of area [m 4 [[]]<000​​​​​​​​​​​​​​​​​​​​​​By substituting the values, the depth b of the cantilever beam does not affect the resonant frequency f0, so the resonant frequency f0 can be determined solely by the length l and thickness h of the cantilever beam. Therefore, by selecting the length l and thickness h of the cantilever beam so that this resonant frequency f0 becomes the desired frequency, a rough design of the ultrasonic actuator 11 can be achieved.

[0049] However, in actual design, it is necessary to consider the influence of layers other than single-crystal silicon (Si) and the anisotropy of the material, so the resonant frequency is adjusted by performing finite element method simulations.

[0050] Next, the array arrangement of the ultrasonic actuators 11 will be described.

[0051] Figure 6 shows an example of an array arrangement of ultrasonic actuators 11. In the example shown in Figure 6, rectangular ultrasonic actuators 11, with their longer sides parallel in the y-direction, are arranged in a rectangular grid. In the example shown in Figure 6, we will describe a case where all ultrasonic actuators 11 are wired independently and each ultrasonic actuator 11 can be controlled by an independent electrical signal.

[0052] d in Figure 6 x d y This represents the distance in the x and y directions, respectively, between the intersection points of the lines representing each row of the ultrasonic actuator 11 in the x direction and the lines representing each column of the ultrasonic actuator 11 in the y direction. d in Figure 6 diag This represents half the diagonal distance between the intersection points of the lines representing each row of the ultrasonic actuator 11 in the x-direction and the lines representing each column of the ultrasonic actuator 11 in the y-direction. The front direction of the array of ultrasonic actuators 11 is defined as the z-direction in Figure 6, and θ is the angle between the z-axis and the direction in which the ultrasonic beam is emitted.

[0053] Similar to the one-dimensional array shown in Figure 2, the angle θ at which the ultrasonic beam emitted from the ultrasonic array sound source 10 is bent from the front of the array is determined by equation (1). stThis is limited by the following. Unlike the one-dimensional array shown in Figure 2, in a two-dimensional array like the one shown in Figure 6, the direction in which the ultrasonic beam is tilted from the z-axis can be any direction in the xy-plane, and the source spacing d and θ depend on the direction in which the ultrasonic beam is bent. st They are different.

[0054] In the case of an array-shaped ultrasonic array sound source 10 with a rectangular grid arrangement as shown in Figure 6, the diagonal direction (d=d diag ) is the shortest, θ st The angle is large, making it easy to bend the ultrasonic beam to a large angle. Conversely, the angle is the most θ st The reason why the ultrasonic beam is difficult to bend is that the sound source distance d is at its maximum. y This is the y-direction. Therefore, when designing a two-dimensional array sound source so that the ultrasonic beam can be bent by an angle θ or more in any direction, equation (1) gives d=d y As, θ≦θ st d y It needs to be made smaller.

[0055] Next, we will explain the operation of the ultrasonic actuator 11.

[0056] The ultrasonic actuator 11 applies a voltage through the upper electrode wiring 21 and the lower electrode wiring 20, creating a potential difference between the upper electrode 18 and the lower electrode 19, which deforms the piezoelectric layer 17. This deformation of the piezoelectric layer 17 causes deformation of the diaphragm portion 15. The diaphragm portion 15 deforms in a way that it bends in the z direction as shown in Figure 5. The diaphragm portion 15 has an intrinsic resonant frequency determined by its thickness, dimensions, and rigidity. If the applied voltage contains AC components with a frequency close to the resonant frequency of the diaphragm portion 15, the diaphragm portion 15 undergoes a resonance phenomenon and vibrates with a larger displacement. This vibration generates sound waves on the front surface of the diaphragm portion 15 (in the +z direction as shown in Figure 5).

[0057] By setting the resonant frequency of the diaphragm section 15 to 20 kHz or higher, which is the upper limit of audible sound, the ultrasonic actuator 11 functions as an ultrasonic sound source. Typically, the resonant frequency is designed to be between 140 kHz and 160 kHz, which is the carrier ultrasonic frequency of the parametric speaker 100.

[0058] The diaphragm section 15 can produce various modes with different frequencies and vibration shapes, but the fundamental vibration mode, which does not have nodes in the diaphragm, is the most efficient as a sound source. Therefore, only the fundamental vibration mode is used here, and higher-order modes that have nodes in the diaphragm are not used.

[0059] Furthermore, if the ratio of the long side to the short side of the diaphragm 15 is too large, the resonance frequency of higher-order modes with nodes in the y-direction (as shown in Figure 4) will decrease, and higher-order mode vibrations will occur even in the frequency band of the fundamental vibration mode being used. This is undesirable as it leads to a decrease in sound pressure at specific frequencies. To prevent this, the ratio of the long side to the short side of the diaphragm 15 should be set to 2.4 to 2.8.

[0060] An electrical signal is supplied to each ultrasonic actuator 11, and ultrasonic waves are emitted from each ultrasonic actuator 11. At this time, by appropriately controlling the phase of the electrical signals supplied to each ultrasonic actuator 11, the phases of the ultrasonic waves emitted from each ultrasonic actuator 11 overlap, and a high-intensity ultrasonic beam is formed in front of the ultrasonic array sound source 10. For example, by supplying electrical signals with the same phase to each ultrasonic actuator 11 that have ideally equivalent characteristics, an ultrasonic beam can be emitted in the direction in front of the ultrasonic array sound source 10, and by supplying electrical signals with a phase shift with an appropriate delay according to the position within the ultrasonic array sound source 10, the direction of the ultrasonic beam can be bent.

[0061] The electrical signal supplied to the ultrasonic array sound source 10 in the above operation includes an AC component in the ultrasonic frequency band close to the resonant frequency of the diaphragm 15 in order to vibrate the diaphragm 15. This AC component in the ultrasonic frequency band of the electrical signal is modulated with an audible sound signal to be reproduced as highly directional sound. Modulation methods used at this time include amplitude modulation (AM) and frequency modulation (FM). As a result, each ultrasonic actuator 11 vibrates according to the modulated electrical signal according to the sound to be reproduced, and the ultrasonic beam generated in front of the ultrasonic array sound source 10 also becomes an ultrasonic beam modulated with audible sound. This modulated ultrasonic beam generates audible sound due to the nonlinear effect when it propagates through the air. Since this audible sound is generated on an ultrasonic beam with high directivity, it functions as a parametric speaker 100 with a narrow audible range. In addition, by performing the above-mentioned phase control, the direction of the ultrasonic beam can be bent, and the position of audible sound generation can be controlled.

[0062] As described above, in this embodiment, the structure of the ultrasonic actuator 11 constituting the ultrasonic array sound source 10 is made into a cantilever structure. This reduces the residual stress in the diaphragm portion 15 and reduces the variation in the resonance frequency of the ultrasonic actuator 11 constituting the ultrasonic array sound source 10, thereby preventing a decrease in the ultrasonic sound pressure radiated from the ultrasonic array sound source 10. This is because the ultrasonic emission efficiency of the ultrasonic actuator 11 is high at the resonance frequency, so if the resonance frequency of the ultrasonic actuator 11 varies as a whole in the array, the emission efficiency at a specific frequency will decrease.

[0063] Furthermore, this embodiment has the effect of preventing a decrease in the directivity of the ultrasonic beam emitted from the ultrasonic array sound source 10. In order to form an ultrasonic beam, it is necessary to control the sound waves emitted from the ultrasonic actuators 11 that make up the ultrasonic array sound source 10. However, if there are ultrasonic actuators 11 that make up the ultrasonic array sound source 10 that have different resonant frequencies, even if they are driven with the same electrical signal, the amplitude of the sound pressure emitted from each ultrasonic actuator 11 will be different and the phase will be shifted. Such variations in the characteristics of the sound source make it difficult to control the sound waves emitted from the ultrasonic actuators 11 that make up the ultrasonic array sound source 10 and reduce the directivity of the ultrasonic beam. Therefore, reducing the variation in the resonant frequencies of the ultrasonic actuators 11 that make up the ultrasonic array sound source 10 is advantageous in improving the directivity of the ultrasonic beam.

[0064] Furthermore, in this embodiment, the cantilever structure has the effect of improving the linearity of the MEMS. Linearity here refers to the linearity between the voltage applied to the actuator and the generated sound pressure, as shown in Figure 7. In ultrasonic actuators that do not have a cantilever structure, such as actuators in which the entire outer circumference of the diaphragm is fixed to the support layer, or diaphragms with a double-supported structure even if they have slits in the diaphragm, the influence of geometric nonlinearity caused by the structural deformation of the diaphragm is significant.

[0065] It is desirable that the ultrasonic actuator 11 used as a parametric speaker 100 has good linearity. This is because if the ultrasonic actuator 11 has non-negligible nonlinearity, the amplitude of the output sound pressure waveform will not be proportional to the amplitude of the input voltage signal, resulting in waveform distortion. This will cause a decrease in sound reproduction accuracy when used as a parametric speaker 100.

[0066] Furthermore, while the parametric speaker 100 inherently achieves super-directionality by generating audible sound through slight nonlinearity in the air, if the ultrasonic actuator 11 exhibits strong nonlinearity, audible sound will be generated from the diaphragm portion 15 itself. Because this audible sound has low directivity, it causes sound leakage from the parametric speaker 100. By making the structure of the ultrasonic actuator 11 a cantilever beam, the effect of nonlinearity can be reduced, thus avoiding the above problem.

[0067] Furthermore, in this embodiment, when configuring the ultrasonic array sound source 10 with cantilevered ultrasonic actuators 11, arranging the cantilevered ultrasonic actuators 11 in the same direction within the array arrangement further reduces the variation in the resonance frequencies of the ultrasonic actuators 11. Therefore, it is possible to prevent a decrease in the ultrasonic sound pressure radiated from the ultrasonic array sound source 10 for the reasons mentioned above, and to prevent a decrease in the directivity of the ultrasonic beam. This is because arranging them in the same direction makes them less susceptible to the effects of dimensional deviations during the manufacturing of the ultrasonic actuators 11.

[0068] MEMS are manufactured using semiconductor processes, in which the patterns of each layer constituting the MEMS are repeatedly transferred using photomasks. Because there are minute positional shifts in this patterning, minute shifts also occur in each layer of the manufactured MEMS. As a result, the resonant frequency of the MEMS deviates from the design.

[0069] In an ultrasonic array sound source 10, which consists of cantilevered ultrasonic actuators 11 arranged in a row, if the ultrasonic actuators 11 are oriented in different directions, the degree of translational misalignment of the patterning will differ for each actuator, causing variations in the resonant frequency of the ultrasonic actuators 11 across the entire array. However, by arranging the cantilevered ultrasonic actuators 11 in the same direction, the degree of translational misalignment of the patterning becomes the same for all ultrasonic actuators 11, resulting in less variation in the resonant frequency of the entire array. Even with such a uniform orientation, the influence of rotational misalignment of the patterning on the resonant frequency misalignment is unavoidable, but the effect of rotational misalignment on the resonant frequency misalignment is small and can be ignored.

[0070] As described above, according to this embodiment, by making the ultrasonic actuator 11, which is the sound source, a cantilever beam structure, it is not affected by stress generated during manufacturing, and by arranging the cantilever beams in one direction when arranging them in an array, it is not affected by manufacturing variations, so that the variation in the resonant frequency of the ultrasonic actuator 11 in the array can be reduced, and thus the decrease in directivity can be suppressed. Furthermore, according to this embodiment, by making the wiring 13 connected to multiple cantilever beam ultrasonic actuators 11 in a high-density array independent wiring so that electrical signals can be supplied individually, the direction of audible sound generation of the parametric speaker can be greatly changed.

[0071] In this embodiment, the shape of the diaphragm portion 15 of the ultrasonic actuator 11 is rectangular as shown in Figure 4, but it is not limited to this, and other shapes are also possible. For example, the free end tip of the diaphragm portion 15 of the ultrasonic actuator 11 may be triangular, or the tip of the diaphragm portion 15 of the ultrasonic actuator 11 may be rounded. This has the effect of changing the resonance characteristics of the diaphragm portion 15 of the ultrasonic actuator 11, or changing the length of the slit portion 16 to reduce the effect of resistance due to airflow.

[0072] (Second Embodiment) Next, a second embodiment will be described.

[0073] The second embodiment differs from the first embodiment in that multiple ultrasonic actuators 11 are grouped together and wired. In the following description of the second embodiment, the description of parts that are the same as in the first embodiment will be omitted, and the parts that differ from the first embodiment will be described.

[0074] Figure 8 shows the configuration of an ultrasonic array sound source 10 according to the second embodiment. As shown in Figure 8, the ultrasonic array sound source 10 of this embodiment groups together at least two adjacent ultrasonic actuators 11 that constitute the ultrasonic array sound source 10 into a single actuator unit 12. In the example shown in Figure 8, two adjacent ultrasonic actuators 11 separated by a dashed line constitute a single actuator unit 12 that is electrically connected in parallel with the same wiring 13.

[0075] In the first embodiment of the ultrasonic array sound source 10 shown in Figure 3, the ultrasonic actuators 11 are independently wired by wiring 13, and a configuration in which independent electrical signals are supplied is shown. On the other hand, in this embodiment, as shown in Figure 8, the ultrasonic array sound source 10 has multiple adjacent ultrasonic actuators 11 that make up the array electrically wired in parallel by wiring 13.

[0076] If we ignore non-idealities such as differences in the resonant frequencies of the ultrasonic actuators 11, the ultrasonic actuators 11 within the actuator unit 12 will vibrate similarly with aligned phases because they are supplied with the same electrical signal. As a result, the actuator unit 12 functions as a sound source with a diaphragm area approximately equal to the sum of the diaphragm area of ​​the individual ultrasonic actuators 11 belonging to the actuator unit 12.

[0077] As described above, grouping multiple ultrasonic actuators 11 into an actuator unit 12 has the effect of reducing the number of independent control points. Too many independent control points can cause problems such as difficulty in electrical control and difficulty in routing wiring. However, simply reducing the number of ultrasonic actuators 11 that make up the ultrasonic array sound source 10 is undesirable because it can lead to insufficient ultrasonic sound pressure or a decrease in the directivity of the ultrasonic beam.

[0078] Therefore, in this embodiment, by grouping multiple ultrasonic actuators 11 into an actuator unit 12, the number of independent control points can be reduced without reducing the number of ultrasonic actuators 11 that constitute the ultrasonic array sound source 10.

[0079] However, compared to the case where all ultrasonic actuators 11 are wired independently by wiring 13, when multiple ultrasonic actuators 11 are grouped into an actuator unit 12, the distance between each control point becomes larger, which increases the angle θ at which the ultrasonic beam can be bent. st The performance decreases. Therefore, when using the actuator unit 12, the design of the arrangement of the ultrasonic actuators 11 as described in Figure 6 must be done using the center distance of the actuator unit 12, rather than the center distance of the individual ultrasonic actuators 11.

[0080] [Differentiation] Figure 9 shows a modified example of wiring to an array of ultrasonic actuators 11. The example shown in Figure 9 is one in which two ultrasonic actuators 11 adjacent to each other in the short-side direction are treated as a single actuator unit 12.

[0081] As shown in Figure 9, if two ultrasonic actuators 11 adjacent to each other in the short-side direction are treated as one actuator unit 12, the angle θ at which the ultrasonic beam can be bent is as follows. stThis makes it less likely to decrease compared to the case where two ultrasonic actuators 11 adjacent to each other in the long-side direction of the ultrasonic actuator 11 are made into a single actuator unit 12.

[0082] Each actuator unit 12, which is an independent control unit, is connected to an individual lower electrode wiring 20. In order to control each actuator unit 12 independently, it is necessary to supply an independent electrical signal to each, so the lower electrode wiring 20 must be wired independently to each actuator unit 12. On the other hand, the upper electrode wiring 21 can be common, so multiple actuator units 12 can be wired together. In Figure 9, the lower electrode wiring 20, shown as a thick line, is connected to a total of eight ultrasonic actuators 11.

[0083] (Third embodiment) Next, a third embodiment will be described.

[0084] The third embodiment differs from the first and second embodiments in that the diaphragm portions 15 of the ultrasonic actuator 11 are arranged facing each other within the actuator unit 12. In the following description of the third embodiment, the descriptions of parts identical to those of the first and second embodiments will be omitted, and the parts that differ from the first and second embodiments will be described.

[0085] Figure 10 is a schematic plan view showing the structure of an ultrasonic actuator 11 in an actuator unit 12 according to a third embodiment. As shown in Figure 10, in the actuator unit 12 of this embodiment, the two ultrasonic actuators 11 are arranged within the actuator unit 12 with the free ends of the diaphragm portions 15 facing each other via a slit portion 16.

[0086] As shown in Figure 10, the two ultrasonic actuators 11 constituting the actuator unit 12 share a cavity 23 without a support layer 22 between the opposing diaphragm portions 15. This arrangement has several advantages. First, by eliminating the partition portion that would be the support layer 22 between the two diaphragm portions 15, the ratio of the diaphragm portions 15 to the ultrasonic array sound source 10 can be increased, improving the ultrasonic generation efficiency per unit area. Second, by eliminating the partition portion that would be the support layer 22, the distance between the two ultrasonic actuators 11 can be reduced, allowing the ultrasonic beam to be bent at an angle θ. st It can be made larger.

[0087] Another effect is that it reduces the influence of airflow resistance on the vibration of the diaphragm portion 15. In an ultrasonic actuator 11 with a cantilever beam structure, as shown in Figure 4, where the diaphragm portion 15 is surrounded by a diaphragm support portion 24 and one side has a fixed end 25 fixed to the diaphragm support portion 24, airflow is generated in the slit portion 16 when the diaphragm portion 15 vibrates. This can cause damping of the vibration of the diaphragm and is undesirable. Therefore, as shown in Figure 10, if the diaphragm portions 15 of the two ultrasonic actuators 11 constituting the actuator unit 12 are placed facing each other, if the two diaphragm portions 15 vibrate in the same way, the generation of airflow in the slit portion 16 in the center of the two diaphragm portions 15 will be small, and the influence of airflow resistance can be reduced.

[0088] However, in the configuration shown in Figure 10, the orientation of the two diaphragm sections 15 is not the same, so there is a risk that the resonant frequencies of the two diaphragm sections 15 will be shifted due to the effects of mask misalignment during MEMS manufacturing as described above. Therefore, when adopting the configuration shown in Figure 10, it is necessary to use a manufacturing process that minimizes mask misalignment.

[0089] (Fourth embodiment) Next, a fourth embodiment will be described.

[0090] The fourth embodiment differs from the first to third embodiments in that, when arranged in an array, the spacing between the ultrasonic actuators 11 within the ultrasonic array sound source 10 is not constant. In the following description of the fourth embodiment, the parts that are the same as those of the first to third embodiments will be omitted, and the parts that differ from the first to third embodiments will be described.

[0091] Figure 11 shows the configuration of the ultrasonic array sound source 10 according to the fourth embodiment. A specific example of when the spacing between ultrasonic actuators 11 within the ultrasonic array sound source 10 is not constant when they are arranged in an array is shown below.

[0092] As shown in Figure 11(a), when the ultrasonic array sound source 10 has the sound wave actuators 11 arranged in an array, the spacing between at least one of the rows in which the multiple ultrasonic actuators 11 are arranged (for example, the spacing between the ultrasonic actuators 11 that make up the central part of the array arrangement) may be wider than the spacing between the other rows.

[0093] Furthermore, when the ultrasonic array sound source 10 has the sound wave actuators 11 arranged in an array, the spacing between at least one of the rows in which the ultrasonic actuators 11 are arranged may be wider than the spacing between the other rows.

[0094] Furthermore, when the ultrasonic array sound source 10 arranges the sound wave actuators 11 in an array, the spacing between at least one of the multiple rows in which the ultrasonic actuators 11 are arranged may be wider than the spacing between the other rows, and the spacing between at least one of the multiple rows in which the ultrasonic actuators 11 are arranged may be wider than the spacing between the other rows.

[0095] Furthermore, as shown in Figure 11(b), when the ultrasonic array sound source 10 is arranged in an array, the arrangement may be such that the spacing between the columns and rows of the ultrasonic actuators 11 becomes denser towards the center, and the spacing between the columns and rows of the ultrasonic actuators 11 becomes sparser towards the outer edges.

[0096] Furthermore, when arranging the ultrasonic array sound source 10 in an array, the ultrasonic actuators 11 may be arranged such that the spacing between the columns and rows of the ultrasonic actuators 11 becomes denser towards the center, or the spacing between the columns and rows of the ultrasonic actuators 11 becomes sparser towards the outer edges.

[0097] Figure 6 illustrates the case where the ultrasonic actuators 11 constituting the ultrasonic array sound source 10 are arranged in a rectangular grid. When the ultrasonic actuators 11 within the ultrasonic array sound source 10 are arranged at regular intervals, the angle θ at which the ultrasonic beam can be bent is as described above. st While this makes calculations easier, the spacing between the ultrasonic actuators 11 does not need to be constant. This has the effect of relaxing the constraints on the placement of ultrasonic actuators 11 within the sound wave array sound source 10, making the design easier. For example, it is possible to intentionally widen the spacing between some ultrasonic actuators 11 to make it easier to run wiring.

[0098] However, if the spacing between the ultrasonic actuators 11 within the ultrasonic array sound source 10 is not constant, the angle θ at which the ultrasonic beam can be bent will differ from the case where the ultrasonic actuators 11 are arranged at equal intervals. st This cannot be calculated from equation (1). It is necessary to perform calculations that superimpose the sound fields emitted from each ultrasonic actuator 11, which acts as a sound source, and determine the placement of the ultrasonic actuators 11 while checking the beam pattern of the ultrasonic beams.

[0099] (Fifth embodiment) Next, a fifth embodiment will be described.

[0100] The fifth embodiment is a digital signage system equipped with a parametric speaker 100 from any of the first to fourth embodiments. In the following description of the fifth embodiment, the descriptions of parts that are the same as those of the first to fourth embodiments will be omitted, and the parts that differ from the first to fourth embodiments will be described.

[0101] Figure 12 is a schematic diagram showing an example of the configuration of a digital signage according to the fifth embodiment. The digital signage shown in Figure 12 includes a parametric speaker 100 and a camera 510 for object recognition. The digital signage 500 of this embodiment analyzes the characteristics of a person captured by the camera 510 and transmits audio information via the parametric speaker 100 so that the audio is heard only by target persons who meet specific conditions.

[0102] Specifically, the digital signage 500 estimates the head position of the subject from the image acquired by the camera 510 and controls the directionality of the ultrasonic beam of the parametric speaker 100 so that an audible sound is generated at that head position. By repeating the above process continuously or intermittently, the digital signage 500 can make the position of the audible sound generation follow the head position of the subject even when the subject is moving.

[0103] This allows the Digital Signage 500 to enhance advertising effectiveness by selectively transmitting audio information to target individuals while preventing sound leakage to others. Furthermore, the Digital Signage 500 enhances the confidentiality of information transmission and reduces ambient noise.

[0104] (Sixth embodiment) Next, a sixth embodiment will be described.

[0105] The sixth embodiment is one in which a parametric speaker 100 of any of the first to fourth embodiments is mounted on a warning device. In the following description of the sixth embodiment, the description of parts that are the same as those of the first to fourth embodiments will be omitted, and the parts that differ from the first to fourth embodiments will be described.

[0106] Figure 13 is a schematic diagram showing an example of the configuration of a warning device 600 according to the sixth embodiment. The warning device 600 shown in Figure 13 comprises a parametric speaker 100 and a camera 610 for object recognition. The warning device 600 of this embodiment analyzes the characteristics of a person captured by the camera 610 and controls the directionality of the parametric speaker 100 so that the sound is heard only by the target person.

[0107] Specifically, the warning device 600 estimates the head position of the subject from the image acquired by the camera 610 and controls the directionality of the ultrasonic beam of the parametric speaker 100 so that an audible sound is generated at that head position. By repeating the above process continuously or intermittently, the warning device 600 can make the location of the audible sound generation follow the head position of the subject even when the subject is moving.

[0108] This allows the alerting device 600 to prompt a selected person to take a specific action, or conversely, to issue a warning to prevent a specific action. The alerting device 600 may have a human remotely determine the target person and the content of the voice message, or it may incorporate edge AI to perform these tasks on the alerting device 600 side.

[0109] (Seventh Embodiment) Next, a seventh embodiment will be described.

[0110] The seventh embodiment is a simultaneous interpretation device equipped with a parametric speaker 100 from any of the first to fourth embodiments. In the following description of the seventh embodiment, the same parts as those in the first to fourth embodiments will be omitted, and the parts that differ from the first to fourth embodiments will be described.

[0111] Figure 14 is a schematic diagram showing an example of the configuration of a simultaneous interpretation device 700 according to the seventh embodiment. The simultaneous interpretation device 700 shown in Figure 14 includes a parametric speaker 100, a camera 710 for object recognition, and a microphone 720. The simultaneous interpretation device 700 of this embodiment analyzes the characteristics of a person captured by the camera 710 and controls the directionality of the parametric speaker 100 so that the audio is heard only by the target person.

[0112] The simultaneous interpretation device 700 acquires the voices of users conversing in different languages ​​using the microphone 720, and transmits the translated voice of the acquired voice to the conversation participants using the directional voice output of the parametric speaker 100. As a result, conversation participants can hear the conversation voice translated into their native language from the simultaneous interpretation device 700 without having to wear earphones.

[0113] Specifically, the simultaneous translation device 700 estimates the head position of the conversation participant from the image acquired by the camera 710, and controls the directionality of the ultrasonic beam of the parametric speaker 100 so that an audible sound is generated at that head position. By repeating the above process continuously or intermittently, the simultaneous translation device 700 can make the location of the audible sound generation follow the head position of the conversation participant even when the conversation participant is moving.

[0114] (Eighth embodiment) Next, an eighth embodiment will be described.

[0115] The eighth embodiment is a parametric speaker 100 of any of the first to fourth embodiments mounted on a directional sound source. In the following description of the eighth embodiment, the description of parts that are the same as those of the first to fourth embodiments will be omitted, and the parts that differ from the first to fourth embodiments will be described.

[0116] Figure 15 is a schematic diagram showing an example of the configuration of a directional sound source 800 according to the eighth embodiment. The directional sound source 800 shown in Figure 15 comprises a parametric speaker 100 and a camera 810. The directional sound source 800 is intended for sound reproduction and sound image generation from an arbitrary position.

[0117] In this embodiment, the directional sound source 800 emits directional sound from the parametric speaker 100 toward an object O selected from the image captured by the camera 810, and the directional sound is reflected and scattered by the selected object O. As a result, the directional sound source 800 can give the listener an auditory experience as if the sound is being reproduced from the object O from which the directional sound is being emitted.

[0118] (Ninth Embodiment) Next, a ninth embodiment will be described.

[0119] The ninth embodiment is a parametric speaker 100 of any of the first to fourth embodiments mounted on a notebook-type personal computer 900. In the following description of the ninth embodiment, the description of parts that are the same as those of the first to fourth embodiments will be omitted, and the parts that differ from the first to fourth embodiments will be described.

[0120] Figure 16 is a schematic diagram showing an example of the configuration of a notebook-type personal computer 900 according to the ninth embodiment. The notebook-type personal computer 900 shown in Figure 16 includes a parametric speaker 100 and a camera 910 for object recognition. In this embodiment, the notebook-type personal computer 900 estimates the head position of user U using the camera 910 and controls the directionality of the parametric speaker 100 so that it generates audible sound only in the vicinity of user U's ear E.

[0121] This allows voice transmission to be performed only to user U, who is using the notebook-type personal computer 900. Furthermore, by continuously or intermittently repeating the above process, the notebook-type personal computer 900 can track the position of the audible sound generation even as user U moves their head.

[0122] Examples of the present invention are as follows: <1> An ultrasonic generator that emits an ultrasonic beam, A sound source in the form of a cantilever structure created by a MEMS (Micro Electro Mechanical Systems) process, comprising multiple cantilever vibrators arranged in an array, Wiring connected to each of the cantilevered vibrators so as to allow for the supply of electrical signals to each of them individually, Equipped with, The plurality of cantilevered vibrators emit ultrasonic waves that form the ultrasonic beam in response to the supply of the electrical signal. An ultrasonic generator characterized by having the following features. <2> Multiple cantilevered vibrators are arranged in the same direction within the array configuration. Characterized by <1> The ultrasonic generator described above. <3> At least two adjacent cantilevered vibrating bodies are grouped together as one group. The aforementioned wiring supplies electrical signals in groups. Characterized by <1> or <2> The ultrasonic generator described above. <4> The cantilevered vibrating body has a rectangular shape, At least two of the cantilevered vibrating bodies adjacent to each other in the short-side direction are considered to be one group. Characterized by <3> The ultrasonic generator described above. <5> The two cantilevered vibrators, which are grouped together, have their free ends facing each other with a gap in between. Characterized by <3> The ultrasonic generator described above. <6> When the cantilevered vibrators are arranged in an array, they are arranged such that at least one of the following is applied: the spacing between at least one of the multiple rows in which the cantilevered vibrators are arranged is wider than the spacing between the other rows; or the spacing between at least one of the multiple rows in which the cantilevered vibrators are arranged is wider than the spacing between the other rows. Characterized by <1> or <5> An ultrasonic generator as described in any one of the following. <7> When the cantilevered vibrators are arranged in an array, they are arranged such that the spacing between the rows and columns of the cantilevered vibrators becomes denser towards the center, or so the spacing between the rows and columns of the cantilevered vibrators becomes sparser towards the outer edges. Characterized by <1> or <5> An ultrasonic generator as described in any one of the following. <8> <1> or <7> An ultrasonic generator as described in any one of the following, A control unit capable of controlling the directivity of the ultrasonic generator, A highly directional speaker characterized by having the following features. [Explanation of Symbols]

[0123] 10. Ultrasonic generator 11. Cantilevered Vibrating Body 13 Wiring 50 Control Unit 100 Super-directional Speakers [Prior art documents] [Patent Documents]

[0124] [Patent Document 1] Japanese Patent Publication No. 2012-029097 [Patent Document 2] Japanese Patent Publication No. 2008-020429

Claims

1. An ultrasonic generator that emits an ultrasonic beam, A sound source in the form of a cantilever structure created by the MEMS (Micro Electro Mechanical Systems) process, comprising multiple cantilever vibrators arranged in an array, Wiring connected to each of the cantilevered vibrators so as to allow for the supply of electrical signals to each of them individually, Equipped with, The plurality of cantilevered vibrators emit ultrasonic waves that form the ultrasonic beam in response to the supply of the electrical signal. An ultrasonic generator characterized by having the following features.

2. Multiple cantilevered vibrators are arranged in the same direction within the array configuration. The ultrasonic generator according to feature 1.

3. At least two adjacent cantilevered vibrating bodies are grouped together as one group. The aforementioned wiring supplies electrical signals in groups. The ultrasonic generator according to feature 1.

4. The cantilevered vibrating body has a rectangular shape, At least two of the cantilevered vibrating bodies adjacent to each other in the short-side direction are considered to be one group. The ultrasonic generator according to feature 3.

5. The two cantilevered vibrators, which are grouped together, have their free ends facing each other with a gap in between. The ultrasonic generator according to feature 3.

6. When the cantilevered vibrators are arranged in an array, they are arranged such that at least one of the following is applied: the spacing between at least one of the multiple rows in which the cantilevered vibrators are arranged is wider than the spacing between the other rows; or the spacing between at least one of the multiple rows in which the cantilevered vibrators are arranged is wider than the spacing between the other rows. The ultrasonic generator according to feature 1.

7. When the cantilevered vibrators are arranged in an array, they are arranged such that the spacing between the rows and columns of the cantilevered vibrators becomes denser towards the center, or so the spacing between the rows and columns of the cantilevered vibrators becomes sparser towards the outer edges. The ultrasonic generator according to feature 1.

8. An ultrasonic generator according to any one of claims 1 to 7, A control unit capable of controlling the directivity of the ultrasonic generator, A highly directional speaker characterized by having the following features.

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