Speaker device and display device comprising same

Abstract

The frequencies of carrier waves respectively emitted from a first parametric speaker (300A) and a second parametric speaker (300B) are 100 kHz or greater and are the same as each other. Audible sound reproduced by the first parametric speaker (300A) and audible sound reproduced by the second parametric speaker (300B) have opposite phases from each other. The first parametric speaker (300A) and the second parametric speaker (300B) are arranged at a pitch interval (P) of 10-20 cm in a horizontal direction. The first parametric speaker (300A) and the second parametric speaker (300B) each have a directional property in which there is an angular range of 35° to 60°C in the horizontal direction, centered around the center 0° of the audible sound emission direction, in which the acoustic pressure that decreases from the peak acoustic pressure at the center 0° is 6 db or less.

Description

Speaker device and display device including the same

[0001] The present invention relates to a speaker device and a display device including the same.

[0002] Japanese Patent No. 5943046 (Patent Document 1) is a prior art document that discloses the configuration of a speaker device. The speaker device described in Patent Document 1 includes a parametric speaker, an audio signal analysis means, a frequency setting means, and a modulation means. The parametric speaker receives a modulated signal obtained by modulating an audio signal into the ultrasonic band. The audio signal analysis means analyzes the audio signal. The frequency setting means sets the frequency of the modulated signal based on the analysis result of the audio signal analysis means. The modulation means generates a modulated signal of the set frequency. The audio signal analysis means analyzes the frequency of the audio contained in the audio signal. The frequency setting means sets the frequency of the modulated signal based on the frequency of the audio.

[0003] Patent No. 5943046

[0004] In the speaker device described in Patent Document 1, the first modulated signal and the second modulated signal have different frequencies, and therefore the sound pressures of the audible sounds demodulated from each signal are different. Therefore, there is room for effectively canceling the demodulated audible sounds to prevent the audible sounds from being reproduced in undesired spaces.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a speaker device and a display device equipped with the same that can effectively cancel demodulated audible sound and prevent the audible sound from being reproduced in an undesired space.

[0006] A speaker device according to the present invention includes a first parametric speaker and a second parametric speaker. The first parametric speaker reproduces audible sound by modulating and driving an ultrasonic transducer. The second parametric speaker reproduces audible sound by modulating and driving an ultrasonic transducer. The frequencies of the carrier waves radiated from the first parametric speaker and the second parametric speaker are equal to or higher than 100 kHz. The audible sounds reproduced by the first parametric speaker and the second parametric speaker are in opposite phase to each other. The first parametric speaker and the second parametric speaker are arranged at a pitch interval of 10 cm to 20 cm in the horizontal direction. Each of the first parametric speaker and the second parametric speaker has a directivity in an angular range of 35° to 60° centered on the central 0° in the horizontal direction, within which the sound pressure that drops from the peak sound pressure at the central 0° in the radiation direction of the audible sound is 6 dB or less.

[0007] According to the present invention, demodulated audible sounds can be effectively cancelled, and reproduction of the audible sounds in undesired spaces can be suppressed.

[0008] 9 is a longitudinal sectional view showing the configuration of an ultrasonic transducer having one ultrasonic vibrator. It is an exploded perspective view showing the configuration of an ultrasonic transducer having one ultrasonic vibrator. It is a perspective view showing the configuration of a frame included in an ultrasonic transducer having one ultrasonic vibrator. It is a sectional view showing the configuration of an ultrasonic vibrator. It is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer having one ultrasonic vibrator is transmitting or receiving ultrasonic waves. It is a sectional view of the ultrasonic transducer of FIG. 5 as seen from the direction of the arrows VI-VI. It is a graph obtained by simulating and analyzing, using the finite element method, the transition of the resonance frequency of the first diaphragm when the longitudinal dimension is changed while the short side dimension inside the frame is fixed. It is a graph obtained by simulating and analyzing, using the finite element method, the transition of the sound pressure of ultrasonic waves transmitted from the ultrasonic transducer when the longitudinal dimension is changed while the short side dimension inside the frame is fixed. It is a side view showing the configuration of an ultrasonic transducer included in a parametric speaker according to a first embodiment of the present invention. It is a rear view of the ultrasonic transducer shown in FIG. 9 as seen from the direction of the arrow X. 1 is an exploded perspective view showing a stacked state in a process of stacking and bonding each component of the ultrasonic transducer included in the parametric speaker according to embodiment 1 of the present invention. FIG. 2 is a plan view showing a positional relationship in a first direction (X-axis direction) in a process of cutting a piezoelectric body of the ultrasonic transducer included in the parametric speaker according to embodiment 1 of the present invention. FIG. 3 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer included in the parametric speaker according to embodiment 1 of the present invention is transmitting or receiving ultrasonic waves. FIG. 4 is a perspective view showing a configuration of an ultrasonic element array according to a comparative example. FIG. 5 is a graph showing actual measurements of the transition of attenuation of sound pressure level over propagation distance in the ultrasonic transducer according to this embodiment and an ultrasonic element array according to the comparative example. FIG. 6 is a graph showing actual measurements of the directivity in the horizontal direction (longitudinal direction) of ultrasonic waves transmitted from the ultrasonic transducer according to this embodiment. FIG. 7 is a graph showing actual measurements of the directivity in the vertical direction (transverse direction) of ultrasonic waves transmitted from the ultrasonic transducer according to this embodiment.1 is a perspective view showing the configuration of a parametric speaker according to a first embodiment of the present invention; FIG. 2 is a graph showing actual measurements of the directivity of audible sound emitted from the parametric speaker according to the present embodiment; FIG. 3 is a plan view illustrating a reproduction area of ​​audible sound emitted from a speaker device according to an embodiment of the present invention; FIG. 4 is a plan view illustrating the directivity of the speaker device according to the present embodiment; FIG. 5 is a graph showing actual measurements of the directivity of audible sound reproduced from a speaker device when the audible sound reproduced by the first parametric speaker and the audible sound reproduced by the second parametric speaker are in phase; FIG. 6 is a graph showing actual measurements of the directivity of audible sound reproduced from a speaker device when the audible sound reproduced by the first parametric speaker and the audible sound reproduced by the second parametric speaker are in opposite phase; and FIG. 7 is a graph showing actual measurements of the transition of attenuation of sound pressure level over propagation distance when the pitch interval P is 5 cm and the frequency of the audible sound is 1 kHz. 1 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 10 cm and the audible sound frequency is 1 kHz. 2 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 15 cm and the audible sound frequency is 1 kHz. 3 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 20 cm and the audible sound frequency is 1 kHz. 4 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 5 cm and the audible sound frequency is 2 kHz. 5 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 10 cm and the audible sound frequency is 2 kHz. 6 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 15 cm and the audible sound frequency is 2 kHz. 1 is a graph showing actual measurements of the transition of attenuation of sound pressure level over propagation distance when the pitch interval P is 20 cm and the audible sound frequency is 2 kHz; 2 is a graph showing actual measurements of the transition of attenuation of sound pressure level over propagation distance when the pitch interval P is 5 cm and the audible sound frequency is 3 kHz; and 3 is a graph showing actual measurements of the transition of attenuation of sound pressure level over propagation distance when the pitch interval P is 10 cm and the audible sound frequency is 3 kHz.1 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 15 cm and the audible sound frequency is 3 kHz. 2 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 20 cm and the audible sound frequency is 3 kHz. 3 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 5 cm and the audible sound frequency is 1 kHz. 4 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 10 cm and the audible sound frequency is 1 kHz. 5 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 15 cm and the audible sound frequency is 1 kHz. 6 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 20 cm and the audible sound frequency is 1 kHz. 1 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 5 cm and the audible sound frequency is 2 kHz. 2 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 10 cm and the audible sound frequency is 2 kHz. 3 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 15 cm and the audible sound frequency is 2 kHz. 4 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 20 cm and the audible sound frequency is 2 kHz. 5 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 5 cm and the audible sound frequency is 3 kHz. 6 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 10 cm and the audible sound frequency is 3 kHz. 1 is a graph showing actual measurements of the transition of sound pressure level with propagation distance when the pitch interval P is 15 cm and the frequency of audible sound is 3 kHz. FIG. 2 is a graph showing actual measurements of the transition of sound pressure level with propagation distance when the pitch interval P is 20 cm and the frequency of audible sound is 3 kHz. FIG. 3 is a plan view for explaining the reproduction area of ​​audible sound emitted from a speaker device according to a modified example of one embodiment of the present invention. FIG. 4 is a block diagram showing the configuration of an amplitude modulation circuit provided in the speaker device according to one embodiment of the present invention. FIG. 5 is a block diagram showing the configuration of an amplitude modulation circuit according to a comparative example.The display device according to the present invention is provided with a speaker device for reproducing audible sound from a speaker unit provided in the display device. The display device according to the present invention is provided with a speaker unit ...

[0009] A speaker device and a display device including the same according to an embodiment of the present invention will be described below with reference to the drawings. In the following description of the embodiment, the same or corresponding parts in the drawings are designated by the same reference numerals, and the description thereof will not be repeated.

[0010] First, the configuration of an ultrasonic transducer having one ultrasonic vibrator will be described. Fig. 1 is a longitudinal cross-sectional view showing the configuration of an ultrasonic transducer having one ultrasonic vibrator. Fig. 2 is an exploded perspective view showing the configuration of an ultrasonic transducer having one ultrasonic vibrator. As shown in Figs. 1 and 2, an ultrasonic transducer 100 having one ultrasonic vibrator includes a first diaphragm 110, a frame 120, and an ultrasonic vibrator 130.

[0011] The first diaphragm 110 has a flat plate shape and is made of an aluminum alloy such as aluminum-containing duralumin, or a metal such as stainless steel. The thickness of the first diaphragm 110 is, for example, 0.1 mm or more and 0.2 mm or less.

[0012] The frame body 120 has a rectangular annular shape. The frame body 120 has a short side direction along a first direction (X-axis direction) and a long side direction along a second direction (Y-axis direction). The frame body 120 extends in the second direction (Y-axis direction). The axial direction of the frame body 120 is along a third direction (Z-axis direction). One end of the frame body 120 in the third direction (Z-axis direction) is bonded to the first diaphragm 110 with a bonding agent made of epoxy resin or the like.

[0013] The frame body 120 is formed from a metal such as an aluminum alloy or stainless steel, glass epoxy, or resin. From the viewpoint of suppressing changes in the characteristics of the ultrasonic transducer 100 due to temperature changes, the frame body 120 is preferably made of metal. On the other hand, from the viewpoint of lowering the frequency of the ultrasonic waves transmitted or received by the ultrasonic transducer 100 and from the viewpoint of miniaturizing the ultrasonic transducer 100, the frame body 120 is preferably made of resin. The thickness of the frame body 120 is, for example, 0.2 mm or more and 0.8 mm or less.

[0014] 3 is a perspective view showing the configuration of a frame body provided in an ultrasonic transducer having one ultrasonic vibrator. As shown in FIG. 3, the frame body 120 has a pair of long sides 121 extending in the second direction (Y-axis direction) and a pair of short sides 122 extending in the first direction (X-axis direction). The average distance between the short sides 122 is four or more times the shortest distance between the long sides 121. In other words, the longitudinal dimension La in the second direction (Y-axis direction) inside the frame body 120 is four or more times the lateral dimension Lb in the first direction (X-axis direction) inside the frame body 120.

[0015] The corners between the long side portion 121 and the short side portion 122 may be chamfered. Furthermore, the short side portion 122 does not have to be linear when viewed from the third direction (Z-axis direction), and may have an arc shape that is convex toward the inside of the frame body 120 or an arc shape that is convex toward the outside of the frame body 120.

[0016] The resonant frequency of the first diaphragm 110 can be adjusted by changing the short-side dimension Lb in the first direction (X-axis direction) inside the frame body 120. For example, when the resonant frequency of the first diaphragm 110 is set to 100 kHz or higher, the short-side dimension Lb is 1.5 mm or more and 3 mm or less.

[0017] The longitudinal dimension La in the second direction (Y-axis direction) inside the frame body 120 is four times or more the short dimension Lb, and from the viewpoint of increasing the sound pressure level of the ultrasound transmitted by the ultrasonic transducer 100, the longitudinal dimension La is, for example, 20 mm or more.

[0018] 1, the ultrasonic vibrator 130 is attached to the frame body 120 and faces the first vibration plate 110 with a gap therebetween. Specifically, the ultrasonic vibrator 130 is attached to the other end of the frame body 120 in the third direction (Z-axis direction), and faces the first vibration plate 110 with the inner space of the frame body 120 sandwiched therebetween.

[0019] FIG. 4 is a cross-sectional view showing the configuration of an ultrasonic vibrator. As shown in FIGS. 1, 2, and 4, the ultrasonic vibrator 130 is a piezoelectric element including a piezoelectric body 131. As shown in FIG. 4, the ultrasonic vibrator 130 includes two stacked piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 are different from each other. Specifically, the polarization directions Dp of the two piezoelectric bodies 131 face each other in the third direction (Z-axis direction). The two piezoelectric bodies 131 are sandwiched between a first electrode 132 and a second electrode 133, and an intermediate electrode 134 is disposed between the two piezoelectric bodies 131. The first electrode 132 and the second electrode 133 are electrically connected to a processing circuit 140 capable of applying an AC voltage. The ultrasonic vibrator 130 is a so-called series-type bimorph piezoelectric vibrator. The total thickness of the two piezoelectric bodies 131 is, for example, 0.5 mm or more and 0.85 mm or less.

[0020] Fig. 5 is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer having one ultrasonic vibrator transmits or receives ultrasonic waves. Fig. 6 is a cross-sectional view of the ultrasonic transducer of Fig. 5 as seen from the direction of the arrows along line VI-VI. The simulation analysis conditions were as follows: the thickness of the first diaphragm 110 was 0.1 mm, the combined thickness of the two piezoelectric bodies 131 was 0.8 mm, the longitudinal dimension La inside the frame body 120 was 20 mm, the lateral dimension Lb was 2 mm, and the thickness of the frame body 120 in the third direction (Z-axis direction) was 0.4 mm.

[0021] 5 and 6, in the vibration mode of the ultrasonic transducer 100, the first diaphragm 110 resonates in an opposite phase to the ultrasonic vibrator 130 in a third direction (Z-axis direction) perpendicular to the first diaphragm 110. That is, as shown in Fig. 6, the displacement direction of the resonant vibration Bm of the first diaphragm 110 and the displacement direction of the resonant vibration Bp of the ultrasonic vibrator 130 are opposite to each other in the third direction (Z-axis direction). The resonant frequencies of the first diaphragm 110 and the ultrasonic vibrator 130 are, for example, 100 kHz or higher.

[0022] In first diaphragm 110, middle portion 110c located at the middle in the longitudinal direction inside frame body 120 becomes the antinode of the resonant vibration, and end portions 110e located at both ends in the longitudinal direction inside frame body 120 become nodes of the resonant vibration. In other words, the portion of first diaphragm 110 located above the internal space of frame body 120 becomes the vibration region that resonates. The longitudinal dimension of the vibration region of first diaphragm 110 is the same as longitudinal dimension La inside frame body 120, and the lateral dimension of the vibration region of first diaphragm 110 is the same as lateral dimension Lb inside frame body 120.

[0023] Here, the relationship between the resonance frequency of the first diaphragm 110 and the longitudinal dimension La inside the frame 120 will be described.

[0024] 7 is a graph showing the results of a simulation analysis using the finite element method of the change in the resonant frequency of the first diaphragm 110 when the longitudinal dimension is changed while the transverse dimension inside the frame is fixed. In FIG. 7, the vertical axis represents the resonant frequency (kHz) of the first diaphragm 110, and the horizontal axis represents the longitudinal dimension La (mm) inside the frame 120. As a condition for the simulation analysis, the transverse dimension Lb inside the frame 120 was fixed at 2 mm.

[0025] 7, when the longitudinal dimension La inside the frame body 120 is 2 mm, the resonant frequency of the first diaphragm 110 is 220 kHz, and when the longitudinal dimension La increases to 8 mm and the longitudinal dimension of the vibration region of the first diaphragm 110 increases, the resonant frequency of the first diaphragm 110 decreases to 122 kHz. Thereafter, even when the longitudinal dimension La inside the frame body 120 exceeds 8 mm and the longitudinal dimension of the vibration region of the first diaphragm 110 further increases, the resonant frequency of the first diaphragm 110 remains approximately constant at 122 kHz.

[0026] In other words, the resonant frequency of the first vibration plate 110 is determined by the speed of sound of the first vibration plate 110 and the reflection of vibration with the frame body 120 as the fixed end, but when the longitudinal dimension La inside the frame body 120 exceeds four times the lateral dimension Lb, the influence of the lateral dimension Lb becomes dominant in terms of the reflection of vibration, and the state of vibration reflection does not change even if the longitudinal dimension La becomes even larger than four times the lateral dimension Lb.

[0027] Next, the results of a simulation analysis using the finite element method on the relationship between the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 100 and the longitudinal dimension La inside the frame body 120 will be described.

[0028] Fig. 8 is a graph showing the results of a simulation analysis using the finite element method of the transition of the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer when the longitudinal dimension is changed while the lateral dimension inside the frame body is fixed. In Fig. 8, the vertical axis shows the sound pressure (Pa) transmitted from the ultrasonic transducer 100, and the horizontal axis shows the longitudinal dimension La (mm) inside the frame body 120. As a simulation analysis condition, the lateral dimension Lb inside the frame body 120 was fixed at 2 mm, and the sound pressure (Pa) was calculated at a position 30 cm away in the third direction (Z-axis direction) from the first diaphragm 110 on the front side of the ultrasonic transducer 100.

[0029] 8, as the longitudinal dimension La inside the frame body 120 increases, the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 100 increases. This means that even when the longitudinal dimension of the vibration region of the first diaphragm 110 is increased, the entire vibration region of the first diaphragm 110 between both end portions 110e vibrates. In other words, the area of ​​the vibration region can be increased by the amount that the vibration region of the first diaphragm 110 is longer, and as a result, the change in air pressure due to the vibration of the first diaphragm 110 can be increased, thereby obtaining a high sound pressure.

[0030] In this way, the ultrasonic transducer 100 can increase the sound pressure while maintaining a substantially constant resonant frequency by increasing the longitudinal dimension of the vibration region of the first diaphragm 110. Furthermore, since there are nodal points at both ends in the longitudinal direction, the ends can be supported or fixed, making it easy to mount the ultrasonic transducer 100.

[0031] The ultrasonic transducer included in the parametric speaker according to the first embodiment of the present invention will be described below with reference to the drawings. The ultrasonic transducer included in the parametric speaker according to the first embodiment of the present invention differs from ultrasonic transducer 100 in that a plurality of ultrasonic vibrators are arranged in an array, and therefore, the description of the configuration that is the same as that of ultrasonic transducer 100 will not be repeated.

[0032] Fig. 9 is a side view showing the configuration of an ultrasonic transducer provided in the parametric speaker according to embodiment 1 of the present invention, Fig. 10 is a rear view of the ultrasonic transducer shown in Fig. 9 as seen from the direction of arrow X.

[0033] 9 and 10 , in an ultrasonic transducer 200 provided in the parametric speaker according to the first embodiment of the present invention, the ultrasonic transducers 100 according to the first embodiment are arranged in an array in a first direction (X-axis direction) and are integrally configured. The ultrasonic transducer 200 includes a first diaphragm 210, a plurality of frame bodies 220, and a plurality of ultrasonic vibrators 130. The plurality of frame bodies 220 are bonded to the first diaphragm 210, and the plurality of ultrasonic vibrators 130 are bonded to the plurality of frame bodies 220, respectively.

[0034] Here, a description will be given of a manufacturing method of the ultrasonic transducer 200. Fig. 11 is an exploded perspective view showing a stacked state in the process of stacking and bonding the components of the ultrasonic transducer included in the parametric speaker according to the first embodiment of the present invention.

[0035] 11 , the first diaphragm 210 has a flat plate shape, and a plurality of slits 211 extending in the second direction (Y-axis direction) are formed at intervals in the first direction (X-axis direction). The first diaphragm 210 is made of an aluminum alloy such as aluminum-containing duralumin, or a metal such as stainless steel. In this embodiment, the first diaphragm 210 is made of stainless steel. The plurality of slits 211 are formed by etching, cutting, or the like.

[0036] Each of the multiple frame bodies 220 has a rectangular ring shape. Each of the multiple frame bodies 220 has a short side direction along a first direction (X-axis direction) and a long side direction along a second direction (Y-axis direction). Each of the multiple frame bodies 220 extends in the second direction (Y-axis direction). The axial direction of each of the multiple frame bodies 220 is along a third direction (Z-axis direction). Each of the multiple frame bodies 220 has a pair of long side portions 221 extending in the second direction (Y-axis direction) and a pair of short side portions 222 extending in the first direction (X-axis direction). The shortest distance between the long side portions 221 is four or more times the shortest distance between the short side portions 222.

[0037] The multiple frame bodies 220 are arranged side by side in a first direction (X-axis direction). A slit 223 is formed between adjacent frame bodies 220 in the first direction (X-axis direction). The multiple slits 223 are formed by etching, cutting, or the like. Adjacent long side portions 221 of adjacent frame bodies 220 in the first direction (X-axis direction) are separated from each other by the slits 223.

[0038] The frame bodies 220 adjacent to each other in the first direction (X-axis direction) are connected to each other at the short side portions 222. That is, among the multiple frame bodies 220, the frame bodies 220 adjacent to each other in the short side direction are connected to each other at both ends in the longitudinal direction.

[0039] Each of the plurality of frame bodies 220 is formed from a metal such as an aluminum alloy or stainless steel, glass epoxy, resin, etc. In this embodiment, the plurality of frame bodies 220 are formed from a single thin plate, but this is not limiting, and the plurality of frame bodies 220, each formed from a plurality of thin plates, may be integrated by joining the short side portions 222 of the frame bodies 220 together.

[0040] In this embodiment, each of the plurality of ultrasonic vibrators 130 includes two stacked piezoelectric bodies 131. As shown in Fig. 11, the two piezoelectric bodies 131 constituting the plurality of ultrasonic vibrators 130 are stacked and bonded in the form of two thin plates.

[0041] 12 is a plan view showing the positional relationship in the first direction (X-axis direction) in the process of cutting the piezoelectric body of the ultrasonic transducer included in the parametric speaker according to Embodiment 1 of the present invention. In FIG. 12, only one piezoelectric body 131 is shown.

[0042] 12, the slits 211 and 223 are arranged at the same position in the first direction (X-axis direction) so as to overlap with each other in the third direction (Z-axis direction). The piezoelectric body 131 is cut and divided by a dicer or the like along a plurality of cut lines LC extending in the second direction (Y-axis direction) so as to overlap with the slits 211 and 223 in the third direction (Z-axis direction). As a result, the ultrasonic transducer 200 shown in FIGS. 9 and 10 is formed.

[0043] FIG. 13 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer included in the parametric speaker according to the first embodiment of the present invention transmits or receives ultrasonic waves.

[0044] 13 , in the first diaphragm 210, intermediate portions 210c located at the middle of the longitudinal direction inside each frame body 220 become antinodes of the resonant vibration, and end portions 210e located at both ends of the longitudinal direction inside each frame body 220 become nodes of the resonant vibration. That is, the portions of the first diaphragm 210 located above the inner spaces of each frame body 220 become vibration regions that resonate. The longitudinal dimension of the vibration region of the first diaphragm 210 is the same as the longitudinal dimension inside each frame body 220, and the lateral dimension of the vibration region of the first diaphragm 210 is the same as the lateral dimension inside each frame body 220.

[0045] Since the ultrasonic transducer 100 has nodal points at both ends in the second direction (Y-axis direction), which is the longitudinal direction, even if the ultrasonic transducers 100 are connected to each other at the both ends to form an array to constitute the ultrasonic transducer 200 according to embodiment 1, the resonant vibration of each ultrasonic transducer 100 is not inhibited. Therefore, by increasing the number of ultrasonic transducers 100 that constitute the ultrasonic transducer 200 according to embodiment 1, the sound pressure level can be easily increased.

[0046] Here, we will explain the results of actual measurements of the relationship between the frequency of ultrasonic waves and the attenuation of the sound pressure level due to the propagation distance. We actually measured the transition of attenuation due to the propagation distance of a 4 kHz audible sound reproduced from ultrasonic waves with a resonant frequency of 146 kHz transmitted from the ultrasonic transducer 200 according to this embodiment, and a 4 kHz audible sound reproduced from ultrasonic waves with a resonant frequency of 40 kHz transmitted from the ultrasonic element array according to the comparative example.

[0047] Fig. 14 is a perspective view showing the configuration of an ultrasonic element array according to a comparative example. As shown in Fig. 14, in the ultrasonic element array according to the comparative example, 50 ultrasonic elements 900 are arranged in a matrix at intervals.

[0048] Fig. 15 is a graph showing actual measurements of the transition of attenuation of sound pressure level over propagation distance in the ultrasonic transducer according to this embodiment and an ultrasonic element array according to a comparative example. In Fig. 15, the vertical axis represents sound pressure level (dB) and the horizontal axis represents propagation distance (cm). The solid line represents data for the ultrasonic transducer 200 according to this embodiment, and the dotted line represents data for the ultrasonic element array according to the comparative example. The sound pressure level is a value normalized by setting the sound pressure level of an audible sound with a frequency of 4 kHz at a point 30 cm away in the third direction (Z-axis direction) from the front of each of the ultrasonic transducer and the ultrasonic element array to 0 dB.

[0049] 15, the audible sound reproduced from the ultrasonic waves having a resonant frequency of 146 kHz transmitted from the ultrasonic transducer 200 according to the present embodiment was attenuated more due to the propagation distance than the audible sound reproduced from the ultrasonic waves having a resonant frequency of 40 kHz transmitted from the ultrasonic element array according to the comparative example. This is because high-frequency ultrasonic waves are easily absorbed by the air as heat, and therefore audible sounds reproduced using high-frequency ultrasonic waves as carrier waves are attenuated more due to the propagation distance.

[0050] In this way, the ultrasonic transducer 200 according to this embodiment, which transmits ultrasonic waves at high frequencies of 100 kHz or higher, can suppress sound from traveling unnecessarily far and suppress sound leakage due to unnecessary reflections, thereby reproducing audible sound only in a limited space. Furthermore, the ultrasonic transducer 200 can increase the attenuation of audible sound over the propagation distance without requiring a configuration for transmitting an opposite-phase carrier wave, allowing for a simple and compact configuration. Furthermore, because ultrasonic waves at high frequencies of 100 kHz or higher are outside the audible range of animals such as dogs and cats, the effects on these animals can be suppressed.

[0051] As shown in Figure 15, in order for audible sound to attenuate after a propagation distance of 30 cm, the Rayleigh distance must be set to 30 cm or less. The Rayleigh distance R0 is given by R0 = (k × a 2 ) / 2, where k is the wave number and a is the radius of the sound source. Therefore, if the speed of sound in air is 340 m / s, when the ultrasonic frequency is 100 kHz, the longitudinal dimension of the vibration region of first diaphragm 210 is 36 mm or less, when the ultrasonic frequency is 150 kHz, the longitudinal dimension of the vibration region of first diaphragm 210 is 29.4 mm or less, and when the ultrasonic frequency is 200 kHz, the longitudinal dimension of the vibration region of first diaphragm 210 is 25.5 mm or less. When the ultrasonic frequency is 100 kHz or more, the longitudinal dimension La is 4 to 24 times the lateral dimension Lb.

[0052] The attenuation effect of audible sound saturates at an ultrasonic frequency of about 200 kHz, and when the ultrasonic frequency is 200 kHz or higher, the resonant frequency of the ultrasonic vibrator 130 varies greatly depending on the variations in the inner dimensions of the frame body 220 and the thickness of the first vibration plate 210. Therefore, it is desirable that the ultrasonic frequency be between 100 kHz and 200 kHz.

[0053] Fig. 16 is a graph showing actual measurements of the horizontal (longitudinal) directivity of ultrasonic waves transmitted from the ultrasonic transducer according to this embodiment. In Fig. 16, the vertical axis represents the sound pressure level (dB) of the ultrasonic waves transmitted from the ultrasonic transducer 200, and the horizontal directivity angle is shown in a semicircular shape.

[0054] 16, the horizontal directionality of the ultrasonic waves transmitted from the ultrasonic transducer 200 is narrow with almost no side lobes generated. This is because the vibration area of ​​the first diaphragm 210 is continuous in the longitudinal direction, so that the sound sources are continuously connected in the longitudinal direction, and interference between the sound sources is continuous, making it difficult for side lobes to be generated.

[0055] Fig. 17 is a graph showing actual measurements of the directivity in the vertical direction (short side direction) of ultrasonic waves transmitted from the ultrasonic transducer according to this embodiment. In Fig. 17, the vertical axis shows the sound pressure level (dB) of the ultrasonic waves transmitted from the ultrasonic transducer 200, and the vertical directivity angle is shown in a semicircular shape.

[0056] 17, side lobes are generated and the vertical directivity of the ultrasonic waves transmitted from the ultrasonic transducer 200 is wide. This is because the vibration area of ​​the first diaphragm 210 is discontinuous in the short side direction, resulting in a state in which sound sources are intermittently present in the short side direction, and interference between the sound sources becomes rough, making it easier for side lobes to be generated.

[0057] Fig. 18 is a perspective view showing the configuration of a parametric speaker according to the first embodiment of the present invention. As shown in Fig. 18, the parametric speaker 300 according to the first embodiment of the present invention has an ultrasonic transducer 200 in which a plurality of ultrasonic vibrators 130, each having a longitudinal direction along the horizontal direction, are arranged in a vertical direction. The parametric speaker 300 is capable of modulating the ultrasonic waves emitted from the ultrasonic transducer 200 by modulating and driving the ultrasonic transducer 200, thereby reproducing audible sound. Modulation methods include AM modulation (amplitude modulation) and FM modulation (frequency modulation).

[0058] The parametric speaker 300 further includes a support 310 that supports the ultrasonic transducer 200. The support 310 includes a pair of joints 311 joined to node points at both longitudinal ends of the ultrasonic transducer 200, and a plurality of connection portions 312 that connect the pair of joints 311 to each other. The pair of joints 311 extend in a first direction (X-axis direction). Because the pair of joints 311 are joined to node points at both longitudinal ends of the ultrasonic transducer 200, the ultrasonic transducer 200 can be supported or fixed without inhibiting vibration of the first diaphragm 210. The plurality of connection portions 312 extend in a second direction (Y-axis direction) while being spaced apart from each other in the first direction (X-axis direction). The plurality of connection portions 312 are positioned at a distance from each other with respect to the first diaphragm 210 so as not to inhibit transmission or reception of ultrasonic waves by the ultrasonic transducer 200.

[0059] Due to the influence of the directionality of the ultrasonic waves transmitted from the ultrasonic transducer 200 shown in Figures 16 and 17, the horizontal directivity H of the audible sound reproduced by the parametric speaker 300 becomes narrower and the vertical directivity V becomes wider, as shown in Figure 18.

[0060] FIG. 19 is a graph showing actual measurements of the directionality of audible sound emitted from the parametric speaker according to this embodiment. In FIG. 19 , the vertical axis represents the sound pressure level (dB) of the audible sound emitted from the parametric speaker 300, and the semicircular shape represents the directivity angle. Measurement conditions included a length of the ultrasonic vibrator 130 in the second direction (Y-axis direction) of 30 mm. The length of the vibration region in the first direction (X-axis direction), which is the short side direction of the ultrasonic transducer 200, was 28.4 mm. The resonant frequency of the ultrasonic vibrator 130 was 100 kHz. The sound pressure level is a normalized value, with the peak sound pressure at the center 0° of the radiation direction of audible sound with a frequency of 1 kHz, measured 30 cm away from the front of the ultrasonic transducer in the third direction (Z-axis direction), being set to 0 dB. Note that due to measurement errors, the peak sound pressure at the center 0° of the radiation direction may not necessarily be the maximum sound pressure.

[0061] 19, the horizontal directivity H of the audible sound reproduced by the parametric speaker 300 had an angle width of 52° up to -6 dB, and the vertical directivity V had an angle width of 75° up to -6 dB. From this result, it was confirmed that the horizontal directivity H of the audible sound reproduced by the parametric speaker 300 was narrow, and the vertical directivity V was wide.

[0062] 20 is a plan view illustrating a reproduction area of ​​an audible sound emitted from a speaker device according to an embodiment of the present invention. As shown in FIG. 20, a speaker device 400 according to an embodiment of the present invention includes a first parametric speaker 300A and a second parametric speaker 300B.

[0063] The first parametric speaker 300A reproduces audible sound by modulating and driving ultrasonic transducers 200 in which a plurality of ultrasonic vibrators 130, each having a longitudinal direction along the horizontal direction (Y-axis direction), are arranged in a line along the vertical direction (X-axis direction). This makes it possible to easily narrow the horizontal directivity of ultrasonic waves transmitted from the ultrasonic transducers 200. However, the arrangement of the ultrasonic transducers 200 in the first parametric speaker 300A is not limited to the above. As will be described later, it is sufficient that the ultrasonic transducers 200 are arranged so as to have directivity in an angle range θA of 35° to 60° centered at 0° in the horizontal direction (Y-axis direction), within which the sound pressure reduction from the peak sound pressure at 0° in the center of the radiation direction of the audible sound is 6 dB or less.

[0064] The second parametric speaker 300B reproduces audible sound by modulating and driving ultrasonic transducers 200 in which a plurality of ultrasonic vibrators 130, each having a longitudinal direction along the horizontal direction (Y-axis direction), are arranged in a line along the vertical direction (X-axis direction). This makes it possible to easily narrow the horizontal directivity of ultrasonic waves transmitted from the ultrasonic transducers 200. However, the arrangement of the ultrasonic transducers 200 in the second parametric speaker 300B is not limited to the above. As will be described later, it is sufficient that the ultrasonic transducers 200 are arranged so as to have directivity in an angle range θB of 35° to 60° centered at 0° in the horizontal direction (Y-axis direction), within which the sound pressure reduction from the peak sound pressure at 0° in the center of the radiation direction of the audible sound is 6 dB or less.

[0065] The frequency of the carrier waves radiated from each of the first parametric speaker 300A and the second parametric speaker 300B is 100 kHz or higher and is the same as each other. The audible sounds reproduced by the first parametric speaker 300A and the second parametric speaker 300B are out of phase with each other. The first parametric speaker 300A and the second parametric speaker 300B are arranged at a pitch interval P in the horizontal direction of 10 cm to 20 cm. The pitch interval P is the distance between the center of the front face of the first parametric speaker 300A and the center of the front face of the second parametric speaker 300B. In this embodiment, the center of the front face of the first parametric speaker 300A and the center of the front face of the second parametric speaker 300B are each located on a baseline BL extending in the horizontal direction (Y-axis direction).

[0066] A central 0° line CA in the radiation direction of audible sound from the first parametric speaker 300A is perpendicular to the baseline BL. The first parametric speaker 300A has directivity with an angular range θA of 35° to 60° centered on the central 0° in the horizontal direction (Y-axis direction), within which the sound pressure reduction from the peak sound pressure at the central 0° in the radiation direction of audible sound is 6 dB or less.

[0067] The center 0° line CB of the audible sound radiation direction of the second parametric speaker 300B is perpendicular to the baseline BL. The second parametric speaker 300B has directivity with an angle range θB of 35° to 60° centered on the center 0° in the horizontal direction (Y-axis direction), within which the sound pressure reduction from the peak sound pressure at the center 0° in the audible sound radiation direction is 6 dB or less.

[0068] In a cancellation region RC where the reproduction region RA of the audible sound radiated from the first parametric speaker 300A and the reproduction region RB of the audible sound radiated from the second parametric speaker 300B overlap, the audible sounds of opposite phase cancel each other out, reducing the sound pressure. Because the distance between the ears 2 of the user 1 of the speaker device is approximately 15 cm, the audible sounds of the reproduction region RA and the reproduction region RB reach the ears 2 of the user 1, who is located at a propagation distance D of 30 cm in the third direction (Z-axis direction) from the baseline BL, while the ears 2 of the user 1, who is located at a propagation distance D of 50 cm, are located in the cancellation region RC, and almost no audible sound reaches the ears 2.

[0069] In the reproduction area RA, an area other than the cancellation area RC where audible sound unnecessarily reaches is defined as a sound leakage area RLA. In the reproduction area RB, an area other than the cancellation area RC where audible sound unnecessarily reaches is defined as a sound leakage area RLB.

[0070] Here, the results of actual measurements of the relationship between the pitch distance P between the first parametric speaker 300A and the second parametric speaker 300B and the attenuation of the sound pressure level of the audible sound reproduced from the speaker device 400 due to the propagation distance D will be described.

[0071] First, the directivity of the audible sound reproduced from the speaker device 400 according to this embodiment will be described. Fig. 21 is a plan view illustrating the directivity of the speaker device according to this embodiment. As shown in Fig. 21, with respect to a central 0° line C that passes through the middle position of the pitch interval P between the first parametric speaker 300A and the second parametric speaker 300B and is perpendicular to the baseline BL, the second parametric speaker 300B side is at a positive angle and the first parametric speaker 300A side is at a negative angle.

[0072] Fig. 22 is a graph showing actual measurements of the directionality of audible sounds reproduced from a speaker device when the audible sounds reproduced by the first parametric speaker and the second parametric speaker are in phase. Fig. 23 is a graph showing actual measurements of the directionality of audible sounds reproduced from a speaker device when the audible sounds reproduced by the first parametric speaker and the second parametric speaker are in opposite phase.

[0073] 22 and 23, the vertical axis represents the sound pressure level (dB) of the audible sound reproduced from the speaker device 400, and the horizontal axis represents the horizontal directivity angle. The pitch interval P between the first parametric speaker 300A and the second parametric speaker 300B is 15 cm, the frequency of the audible sound reproduced from the speaker device 400 is 2 kHz, and the propagation distance D is 30 cm, 50 cm, and 75 cm, respectively. As shown in Figs. 22 and 23, the sound pressure level of the audible sound reproduced from the speaker device 400 at each propagation distance D is taken as the maximum value (peak value) indicated by the arrow.

[0074] In this way, the transition of the attenuation of the sound pressure level depending on the propagation distance D of audible sounds of frequencies of 1 kHz, 2 kHz, and 3 kHz reproduced from the speaker device was measured when the pitch distance P between the first parametric speaker 300A and the second parametric speaker 300B was 5 cm, 10 cm, 15 cm, and 20 cm.

[0075] Fig. 24 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 5 cm and the audible sound frequency is 1 kHz. Fig. 25 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 10 cm and the audible sound frequency is 1 kHz. Fig. 26 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 15 cm and the audible sound frequency is 1 kHz. Fig. 27 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 20 cm and the audible sound frequency is 1 kHz.

[0076] Fig. 28 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 5 cm and the audible sound frequency is 2 kHz. Fig. 29 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 10 cm and the audible sound frequency is 2 kHz. Fig. 30 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 15 cm and the audible sound frequency is 2 kHz. Fig. 31 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 20 cm and the audible sound frequency is 2 kHz.

[0077] Fig. 32 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 5 cm and the audible sound frequency is 3 kHz. Fig. 33 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 10 cm and the audible sound frequency is 3 kHz. Fig. 34 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 15 cm and the audible sound frequency is 3 kHz. Fig. 35 is a graph showing actual measurements of the change in attenuation of sound pressure level over propagation distance when the pitch interval P is 20 cm and the audible sound frequency is 3 kHz.

[0078] 24 to 35, the vertical axis represents sound pressure level (dB) and the horizontal axis represents propagation distance (cm). A solid line represents data when the audible sound reproduced by the first parametric speaker 300A and the audible sound reproduced by the second parametric speaker 300B are out of phase with each other, a dotted line represents data when the audible sound reproduced by the first parametric speaker 300A and the audible sound reproduced by the second parametric speaker 300B are in phase with each other, and a dashed-dotted line represents data from a comparative example in which only one parametric speaker is positioned at the intersection of the baseline BL and the central 0° line C. As in FIGS. 22 and 23, the sound pressure level is taken as the maximum value (peak value).

[0079] As shown in Figures 24 to 35, the attenuation of the audible sound reproduced from the speaker device due to the propagation distance D is greater when the audible sound reproduced by the first parametric speaker 300A and the audible sound reproduced by the second parametric speaker 300B are out of phase with each other than when the audible sound reproduced by the first parametric speaker 300A and the audible sound reproduced by the second parametric speaker 300B are in phase with each other.

[0080] As shown in Figures 31 and 35, when the audible sound reproduced by the first parametric speaker 300A and the audible sound reproduced by the second parametric speaker 300B are in opposite phase, the degree of attenuation of the audible sound reproduced from the speaker device due to the propagation distance D is smaller than the degree of attenuation in the comparative example when the pitch distance P between the first parametric speaker 300A and the second parametric speaker 300B is 20 cm and the frequency of the audible sound is 2 kHz and 3 kHz.

[0081] This is because, as the pitch distance P between the first parametric speaker 300A and the second parametric speaker 300B increases, the sound leakage regions RLA and RLB become wider, and the difference in the propagation path lengths of the audible sounds from the first parametric speaker 300A and the second parametric speaker 300B increases, creating a region where the audible sounds reinforce each other. For this reason, it is preferable that the pitch distance P between the first parametric speaker 300A and the second parametric speaker 300B be 20 cm or less.

[0082] Next, the sound pressure level at each propagation distance D of the audible sound reproduced from the speaker device 400 was taken as the average of the actual measured values ​​at the position of both ears 2, and the changes in sound pressure level depending on the propagation distance D of audible sounds of frequencies 1 kHz, 2 kHz, and 3 kHz reproduced from the speaker device were measured when the pitch distance P between the first parametric speaker 300A and the second parametric speaker 300B was 5 cm, 10 cm, 15 cm, and 20 cm.

[0083] Fig. 36 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 5 cm and the audible sound frequency is 1 kHz. Fig. 37 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 10 cm and the audible sound frequency is 1 kHz. Fig. 38 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 15 cm and the audible sound frequency is 1 kHz. Fig. 39 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 20 cm and the audible sound frequency is 1 kHz.

[0084] Fig. 40 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 5 cm and the audible sound frequency is 2 kHz. Fig. 41 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 10 cm and the audible sound frequency is 2 kHz. Fig. 42 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 15 cm and the audible sound frequency is 2 kHz. Fig. 43 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 20 cm and the audible sound frequency is 2 kHz.

[0085] Fig. 44 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 5 cm and the audible sound frequency is 3 kHz. Fig. 45 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 10 cm and the audible sound frequency is 3 kHz. Fig. 46 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 15 cm and the audible sound frequency is 3 kHz. Fig. 47 is a graph showing actual measurements of the change in sound pressure level over propagation distance when the pitch interval P is 20 cm and the audible sound frequency is 3 kHz.

[0086] 36 to 47, the vertical axis represents sound pressure level (dB) and the horizontal axis represents propagation distance (cm). A solid line represents data when the audible sounds reproduced by the first parametric speaker 300A and the second parametric speaker 300B are out of phase with each other, and a dotted line represents data when the audible sounds reproduced by the first parametric speaker 300A and the second parametric speaker 300B are in phase with each other.

[0087] As shown in Figures 36, 40 and 44, when the pitch distance P between the first parametric speaker 300A and the second parametric speaker 300B is 5 cm, the ears 2 of a user 1 who is located at a position where the propagation distance D of the audible sound reproduced from the speaker device 400 is 30 cm are located in the cancellation region RC, and the sound pressure levels of the audible sounds at all frequencies of 1 kHz, 2 kHz and 3 kHz are low both when the audible sounds reproduced by the first parametric speaker 300A and the second parametric speaker 300B are in phase and when the audible sounds reproduced by the first parametric speaker 300A and the second parametric speaker 300B are out of phase.

[0088] As shown in Figures 37 to 39, when the pitch distance P between the first parametric speaker 300A and the second parametric speaker 300B is 10 cm, 15 cm, or 20 cm and the frequency of the audible sound is 1 kHz, the sound pressure level of the audible sound reproduced from the speaker device 400 over a propagation distance D of 30 cm is lower when the audible sound reproduced by the first parametric speaker 300A and the audible sound reproduced by the second parametric speaker 300B are out of phase with each other than when the audible sound reproduced by the first parametric speaker 300A and the audible sound reproduced by the second parametric speaker 300B are in phase with each other.

[0089] On the other hand, as shown in Figures 41 to 43 and Figures 45 to 47, when the pitch distance P between the first parametric speaker 300A and the second parametric speaker 300B is 10 cm, 15 cm, or 20 cm and the frequency of the audible sound is 2 kHz or 3 kHz, the sound pressure level of the audible sound reproduced from the speaker device 400 over a propagation distance D of 30 cm is higher when the audible sound reproduced by the first parametric speaker 300A and the audible sound reproduced by the second parametric speaker 300B are out of phase with each other than when the audible sound reproduced by the first parametric speaker 300A and the audible sound reproduced by the second parametric speaker 300B are in phase with each other.

[0090] As shown in Figures 24 to 47, in order to ensure a large degree of attenuation of the audible sound reproduced from the speaker device due to the propagation distance D and to ensure the sound pressure level of the audible sound reaching both ears 2 of the user 1, it is preferable that the pitch distance P between the first parametric speaker 300A and the second parametric speaker 300B be 10 cm or more and 20 cm or less.

[0091] In the speaker device 400 according to this embodiment, the frequencies of the carrier waves radiated from the first parametric speaker 300A and the second parametric speaker 300B are equal to or higher than 100 kHz. The audible sounds reproduced by the first parametric speaker 300A and the second parametric speaker 300B are in opposite phase to each other. The first parametric speaker 300A and the second parametric speaker 300B are arranged at a pitch interval P of 10 cm to 20 cm in the horizontal direction. This effectively cancels the demodulated audible sound, preventing the audible sound from being reproduced in an undesired space.

[0092] In the example shown in Figure 20, the central 0° line CA of the radiation direction of the audible sound of the first parametric speaker 300A and the central 0° line CB of the radiation direction of the audible sound of the second parametric speaker 300B are each perpendicular to the baseline BL, but these do not necessarily have to be perpendicular.

[0093] Fig. 48 is a plan view illustrating a reproduction region of an audible sound emitted from a speaker device according to a modified example of one embodiment of the present invention. As shown in Fig. 48, in the speaker device according to the modified example of one embodiment of the present invention, when viewed from the vertical direction (X-axis direction), a central 0° line CA of the emission direction of the audible sound of the first parametric speaker 300A is inwardly oriented at an angle θDA with a virtual reference line XL that is orthogonal to the horizontal direction (Y-axis direction) and is within a range of 0° to 5°, where the outward-facing sides of the first parametric speaker 300A and the second parametric speaker 300B are defined as the outer sides. When viewed from the vertical direction (X-axis direction), the central 0° line CB of the radiation direction of the audible sound of the second parametric speaker 300B forms an angle with the virtual reference line XL that is perpendicular to the horizontal direction (Y-axis direction) within a range of 0° to 5° inward, with the side on which the first parametric speaker 300A and the second parametric speaker 300B face outward being the outer side.

[0094] This makes it possible to narrow each of the sound leakage regions RLA and RLB, while increasing the degree of attenuation of the audible sound reproduced from the speaker device 400 over the propagation distance D.

[0095] From the standpoint of preventing each of sound leakage regions RLA and RLB from becoming too wide, it is preferable that the angle formed by the central 0° line CA, CB in the radiation direction of audible sound from each of the first parametric speaker 300A and the second parametric speaker 300B with respect to a virtual reference line XL that is orthogonal to the horizontal direction (Y axis direction) when viewed from the vertical direction (X axis direction) is within a range of 1° outward to 5° inward, where the outward-facing sides of the first parametric speaker 300A and the second parametric speaker 300B are defined as the outer sides.

[0096] Fig. 49 is a block diagram showing the configuration of an amplitude modulation circuit provided in a speaker device according to one embodiment of the present invention. As shown in Fig. 49, the amplitude modulation circuit according to this embodiment includes a signal generator 500, an audio signal input section 510, an inverting circuit section 520, a first AM modulation circuit section 530A, and a second AM modulation circuit section 530B.

[0097] The signal generator 500 inputs a drive pulse voltage for transmitting a carrier wave to each of the first AM modulation circuit section 530A and the second AM modulation circuit section 530B. The first AM modulation circuit section 530A amplitude-modulates the drive pulse voltage based on the audio signal input from the audio signal input section 510. The drive pulse voltage amplitude-modulated by the first AM modulation circuit section 530A is input to the first parametric speaker 300A.

[0098] The inverting circuit unit 520 inverts the phase of the audio signal input from the audio signal input unit 510. The second AM modulation circuit unit 530B amplitude-modulates the drive pulse voltage based on the audio signal whose phase has been inverted by the inverting circuit unit 520. The drive pulse voltage amplitude-modulated by the second AM modulation circuit unit 530B is input to the second parametric speaker 300B.

[0099] As described above, the first parametric speaker 300A and the second parametric speaker 300B each receive a drive pulse voltage for transmitting a carrier wave from the common signal generator 500. This makes it possible to suppress the generation of noise caused by beats that occur when the frequencies of the carrier waves of the first parametric speaker 300A and the second parametric speaker 300B differ from each other, as in the amplitude modulation circuit according to the comparative example described below.

[0100] Fig. 50 is a block diagram showing the configuration of an amplitude modulation circuit according to a comparative example. As shown in Fig. 50, the amplitude modulation circuit according to the comparative example includes a first signal generator 500A, a second signal generator 500B, an audio signal input section 510, an inverting circuit section 520, a first AM modulation circuit section 530A, and a second AM modulation circuit section 530B.

[0101] The first signal generator 500A inputs a drive pulse voltage for transmitting a carrier wave to the first AM modulation circuit unit 530A. The first AM modulation circuit unit 530A amplitude-modulates the drive pulse voltage based on the audio signal input from the audio signal input unit 510. The drive pulse voltage amplitude-modulated by the first AM modulation circuit unit 530A is input to the first parametric speaker 300A.

[0102] The second signal generator 500B inputs a drive pulse voltage for transmitting a carrier wave to the second AM modulation circuit unit 530B. The inversion circuit unit 520 inverts the phase of the audio signal input from the audio signal input unit 510. The second AM modulation circuit unit 530B amplitude-modulates the drive pulse voltage based on the audio signal whose phase has been inverted by the inversion circuit unit 520. The drive pulse voltage amplitude-modulated by the second AM modulation circuit unit 530B is input to the second parametric speaker 300B.

[0103] As described above, in the amplitude modulation circuit according to the comparative example, because drive pulse voltages are supplied to the first parametric speaker 300A and the second parametric speaker 300B from separate signal generators, the frequencies of the carrier waves of the first parametric speaker 300A and the second parametric speaker 300B may differ by, for example, about 3 kHz, which may result in beats and audible noise.

[0104] Here, a display device including the speaker device according to this embodiment will be described. Fig. 51 is a plan view illustrating a reproduction area of ​​an audible sound emitted from a speaker device included in a display device according to one embodiment of the present invention. Fig. 52 is a schematic diagram showing the configuration of a display device according to one embodiment of the present invention. As shown in Figs. 51 and 52, the display device according to one embodiment of the present invention includes a first parametric speaker 300A, a second parametric speaker 300B, and a display 600.

[0105] The display device is, for example, a television, a personal computer, or various types of operation terminal devices. The display 600 has a display surface 610. The display surface 610 also includes the surface of a frame surrounding the display area. In this embodiment, the first parametric speaker 300A and the second parametric speaker 300B are arranged below the display surface 610. The first parametric speaker 300A and the second parametric speaker 300B can reproduce audible sounds in a certain area on the display surface 610 side of the display 600. As a result, audible sounds reach both ears 2 of the user 1 from the first parametric speaker 300A and the second parametric speaker 300B, respectively.

[0106] As shown in FIGS. 51 and 52, the first parametric speaker 300A and the second parametric speaker 300B are arranged at positions that are line-symmetric in the horizontal direction with respect to a center line CC that passes through the center of the display surface 610 of the display 600.

[0107] The horizontal position of user 1's ear 2 relative to the display surface 610 of the display 600 is relatively small because user 1 is positioned facing the center of the display surface 610. Therefore, by using the first parametric speaker 300A and the second parametric speaker 300B to reproduce audible sounds in a certain area (playback area RA and playback area RB) on the display surface 610 side of the display 600, user 1 can hear the audible sounds stably while preventing the audible sounds from being reproduced in an undesired space. For example, audible sounds from the playback area RA and the playback area RB reach both ears 2 of user 1 located at a propagation distance D of 30 cm in the third direction (Z-axis direction) from the baseline BL. However, both ears 2 of user 1 located at a propagation distance D of 100 cm are located in the cancellation area RC, and almost no audible sounds reach both ears 2. In other words, audible sounds reach user 1 of the display device, while non-users behind user 1 cannot hear the audible sounds.

[0108] Fig. 53 is a schematic diagram showing the configuration of a display device according to a modified example of one embodiment of the present invention. As shown in Fig. 53, in the display device according to the modified example of one embodiment of the present invention, the first parametric speaker 300A and the second parametric speaker 300B are arranged above the display surface 610. In the display device according to this modified example, the first parametric speaker 300A and the second parametric speaker 300B also reproduce audible sounds in certain areas (playback areas RA and RB) on the display surface 610 side of the display 600, thereby enabling the user 1 to hear the audible sounds stably and preventing the audible sounds from being reproduced in undesired spaces.

[0109] (Note) It will be understood by those skilled in the art that the exemplary embodiments described above are specific examples of the following aspects.

[0110] <1> A speaker device comprising: a first parametric speaker that reproduces audible sound by modulating and driving an ultrasonic transducer; and a second parametric speaker that reproduces audible sound by modulating and driving the ultrasonic transducer; wherein the frequencies of carrier waves radiated from the first parametric speaker and the second parametric speaker are equal to or higher than 100 kHz; the audible sounds reproduced by the first parametric speaker and the second parametric speaker are in opposite phase to each other; the first parametric speaker and the second parametric speaker are arranged at a pitch interval of 10 cm to 20 cm in the horizontal direction; and each of the first parametric speaker and the second parametric speaker has directivity with an angular range of 35° to 60° centered on a central 0° in the horizontal direction, where the sound pressure reduction from the peak sound pressure at the central 0° in the radiation direction of the audible sound is 6 dB or less.

[0111] <2> The speaker device according to <1>, wherein in the ultrasonic transducer of the first parametric speaker, a plurality of ultrasonic vibrators having a longitudinal direction along the horizontal direction are arranged to line up along the vertical direction, and in the ultrasonic transducer of the second parametric speaker, a plurality of ultrasonic vibrators having a longitudinal direction along the horizontal direction are arranged to line up along the vertical direction.

[0112] <3> The speaker device according to <1> or <2>, wherein a drive pulse voltage for transmitting the carrier wave is supplied to each of the first parametric speaker and the second parametric speaker from a common signal generator.

[0113] <4> The speaker device according to any one of <1> to <3>, wherein, when viewed from the vertical direction, a central 0° line in the radiation direction of the audible sound of each of the first parametric speaker and the second parametric speaker forms an angle with a virtual reference line that is orthogonal to the horizontal direction, within a range of 1° outward to 5° inward, when the sides on which the first parametric speaker and the second parametric speaker face outward are defined as the outer sides.

[0114] <5> A display device comprising: the speaker device according to any one of <1> to <4>; and a display having a display surface, wherein the first parametric speaker and the second parametric speaker are capable of reproducing audible sounds in a certain region on the display surface side of the display.

[0115] In the above-described embodiments, configurations that can be combined may be combined with each other.

[0116] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0117] 1 User, 2 Ear, 100, 200 Ultrasonic transducer, 110, 210 First diaphragm, 110c, 210c Middle portion, 110e, 210e End portion, 120, 220 Frame body, 121, 221 Long side portion, 122, 222 Short side portion, 130 Ultrasonic vibrator, 131 Piezoelectric body, 132 First electrode, 133 Second electrode, 134 Intermediate electrode, 140 Processing circuit, 211, 223 Slit, 300 Parametric speaker, 300A First parametric speaker, 300B Second parametric speaker, 310 Support, 311 Joint portion, 312 Connection portion, 400 Speaker device, 500 Signal generator, 500A First signal generator, 500B Second signal generator, 510 Audio signal input unit, 520 inversion circuit unit, 530A first modulation circuit unit, 530B second modulation circuit unit, 600 display, 610 display surface, 900 ultrasonic element, BL baseline, LC cut line, La longitudinal dimension, Lb lateral dimension, P pitch interval, R0 Rayleigh distance, RA, RB reproduction area, RC cancellation area, RLA sound leakage area, XL virtual reference line.

Claims

1. A speaker device comprising: a first parametric speaker that reproduces audible sound by modulating and driving an ultrasonic transducer; and a second parametric speaker that reproduces audible sound by modulating and driving an ultrasonic transducer; the frequencies of the carrier waves radiated from the first parametric speaker and the second parametric speaker are 100 kHz or higher and are the same; the audible sounds reproduced by the first parametric speaker and the second parametric speaker are in opposite phase to each other; the first parametric speaker and the second parametric speaker are arranged at a pitch interval of 10 cm or more and 20 cm or less in the horizontal direction; and each of the first parametric speaker and the second parametric speaker has directivity with an angular range of 35° or more and 60° or less centered on the central 0° in the horizontal direction, where the sound pressure reduction from the peak sound pressure at the central 0° in the radiation direction of the audible sound is 6 dB or less.

2. The speaker device according to claim 1, wherein in the ultrasonic transducer of the first parametric speaker, a plurality of ultrasonic vibrators having a longitudinal direction aligned with the horizontal direction are arranged in a line along the vertical direction, and in the ultrasonic transducer of the second parametric speaker, a plurality of ultrasonic vibrators having a longitudinal direction aligned with the horizontal direction are arranged in a line along the vertical direction.

3. A speaker device according to claim 1 or 2, wherein the first parametric speaker and the second parametric speaker are each supplied with a drive pulse voltage for transmitting the carrier wave from a common signal generator.

4. A speaker device as described in any one of claims 1 to 3, wherein the central 0° line of the radiation direction of audible sound from each of the first parametric speaker and the second parametric speaker forms an angle with a virtual reference line perpendicular to the horizontal direction when viewed from the vertical direction, within a range of 1° outward to 5° inward, when the sides on which the first parametric speaker and the second parametric speaker face outward are defined as the outer sides.

5. A display device comprising the speaker device according to any one of claims 1 to 4 and a display having a display surface, wherein the first parametric speaker and the second parametric speaker are capable of reproducing audible sound in a fixed area on the display surface side of the display.

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