JP2007005872A - Ultrasonic speaker system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic speaker system that transduces a waveform of a sound signal into aerial vibration with fidelity to obtain a high output and forms an excellent acoustic environment. <P>SOLUTION: Each of first ultrasonic speakers each for outputting a carrier signal at an ultrasonic band and second ultrasonic speakers each for outputting a modulation signal resulting from frequency-modulating a carrier signal with a sound signal is provided with a drive section 17 for forming a magnetic field at a rear side of a metal-made diaphragm 15. In the drive section 17, a magnet 18 is joined with one-side end parts of pole pieces 19, an outer circumferential coil 20a and an inner circumferential coil 20b each for receiving a supplied signal are wound near the other end parts, and a gap 22 is formed between the other end faces 21 of the pole pieces 19 and the diaphragm 15. When the modulation signal and the carrier signal are respectively applied to the outer circumferential coil 20a and the inner circumferential coil 20b, the magnetic field formed around the other end faces 21 is changed to produce eddy currents on the surface of the diaphragm 15 and Lorentz's forces are produced to vibrate the diaphragm 15. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to an ultrasonic speaker and an electroacoustic conversion technique used for the ultrasonic speaker.

2. Description of the Related Art Conventionally, as a means for outputting sound with high directivity, an ultrasonic speaker system that propagates sound in an audible band in the air using ultrasonic waves as a carrier wave is known. In this ultrasonic speaker system, there is a method in which a carrier signal in the ultrasonic band is amplitude-modulated (AM: Amplitude Modulation) by an audio signal in the audible sound band and output from the speaker, and the sound image of the voice to be propagated is localized in the air. (For example, refer to Patent Document 1). On the other hand, a method has also been proposed in which ultrasonic waves of different frequencies are output simultaneously from a plurality of speakers, the listeners listen to the ultrasonic waves simultaneously, and the listener's eardrum hears the sound of the frequency difference between the ultrasonic waves. (For example, see Non-Patent Document 1).
JP 2005-101749 A Theory, History and The Advancement of Parametric Loudspeakers Rev. E (Authors: James J. Croft, Joseph O. Norris, American Technology Corporation)

  However, according to the amplitude modulation method shown in Patent Document 1, since the waveform of the audio signal is greatly distorted by the modulation, the sound output from the speaker and heard by the listener's ear has poor reproducibility and is good. The acoustic environment cannot be obtained.

  In addition, according to the method described in Non-Patent Document 1, it can be considered that waveform distortion at the signal level can be prevented. In Non-Patent Document 1, however, there is a concept of an audio output method to be applied to an ultrasonic speaker. Is merely presented, and it is not specifically shown by what configuration the ultrasonic speaker can be realized.

  Here, in order to obtain a large output and form a good acoustic environment in the ultrasonic speaker system, it is necessary that the vibration plate of the ultrasonic speaker vibrates without distortion with a large amplitude in the ultrasonic frequency band. . As conventional ultrasonic speakers including the ultrasonic speakers presented in Patent Document 1 and Non-Patent Document 1, electrodynamic speakers and piezoelectric speakers are used. However, an electrodynamic speaker is hindered from high-speed vibration of the diaphragm because a heavy and large volume coil is fixed to the diaphragm, and the piezoelectric speaker is in view of the physical characteristics of the piezoelectric transducer. The sound to be listened to is greatly attenuated in a specific frequency band (especially in the mid-low range) compared to the original sound signal. Therefore, when these speakers are used, there is a problem that a large output cannot be obtained and a favorable acoustic environment cannot be formed.

  The present invention has been made based on such a problem, and in an ultrasonic speaker system, the waveform of an audio signal is faithfully converted into air vibrations to obtain a large output and to form a good acoustic environment. It is an issue.

  In order to achieve the above object, the invention according to claim 1 is an ultrasonic speaker system, comprising: first ultrasonic output means for outputting an ultrasonic band signal; and supply of an audio signal in an audible band. A second ultrasonic output means for outputting an ultrasonic band signal in which the frequency band is continuously changed depending on the received audio signal; and the signal output from the first ultrasonic output means is super A first ultrasonic generator that outputs a sound wave, and a loudspeaker that includes a second ultrasonic generator that outputs an ultrasonic wave according to the signal output from the second ultrasonic output unit. It is characterized by.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect, the first ultrasonic output means is an oscillating means for generating a signal in an ultrasonic band, and the second ultrasonic output means is Frequency modulation means for frequency-modulating a signal in the ultrasonic band with the audio signal and outputting a modulation signal obtained by the frequency modulation; in at least the second ultrasonic generator of the two ultrasonic generators; And a drive unit that vibrates the diaphragm by Lorentz force.

  According to a third aspect of the present invention, in addition to the configuration according to the first or second aspect, the ultrasonic generator provided with the driving unit includes a gap between the diaphragm and the driving unit. It is characterized by that.

  According to a fourth aspect of the present invention, in addition to the configuration according to any one of the first to third aspects, the diaphragm is made of metal.

  According to a fifth aspect of the present invention, the loudspeaker includes a sound generator that outputs an audible sound to the air based on a signal in an audible band, and the first ultrasonic generator around the sound generator. And the second ultrasonic generator is provided.

  According to the first aspect of the present invention, by outputting ultrasonic waves from the first and second ultrasonic generators, high directivity air vibrations are generated from the first and second ultrasonic generators. It emits towards the distance and allows the listener's eardrum to hear the difference between the two ultrasonic waves. Then, the second ultrasonic output means outputs from the second ultrasonic generator the ultrasonic wave whose frequency band is continuously changed depending on the audio signal in the audible band, whereby the first and second It is possible to cause the eardrum of a listener who has simultaneously listened to the ultrasonic waves generated from the ultrasonic generator to hear the change in the difference between the two ultrasonic waves. The ultrasonic wave output from the second ultrasonic wave output means changes in frequency band continuously depending on the audio signal in the audible band, so that the characteristics of the original audio signal are kept faithfully, By outputting the signal from the ultrasonic generator, it is possible to make the listener listen to a high-output sound in which the original sound signal is reproduced with high quality, and a good acoustic environment with high output can be formed.

  According to the second aspect of the present invention, by outputting a modulation signal obtained by frequency-modulating (FM: Frequency Modulation) a carrier signal in the ultrasonic band with an audio signal in the audible band, reproduction of the original audio signal is performed. A modulation signal having high performance and gain can be formed. Then, at least the second ultrasonic generator can vibrate the signal in the ultrasonic region efficiently by causing the diaphragm to vibrate by vibrating the diaphragm with the Lorentz force. Thereby, the reproducibility and gain of the sound heard as a difference sound can be improved, and a better acoustic environment with higher output can be formed.

  According to the third aspect of the present invention, in the ultrasonic generator that vibrates the diaphragm by the Lorentz force, the diaphragm such as a coil is vibrated by providing the gap portion between the diaphragm and the drive unit. Therefore, the diaphragm can be physically separated from another structure having a large mass or volume. Thereby, even a high-speed vibration in the ultrasonic band can be vibrated without causing distortion in the diaphragm, so that the reproducibility and gain of the sound heard as a difference sound is further enhanced, and the output is higher. A better acoustic environment can be formed.

  According to the fourth aspect of the present invention, the diaphragm is made of metal, so that it is difficult for the diaphragm to be physically distorted even with high-speed vibration caused by an ultrasonic band signal. Thereby, it is possible to prevent the sound from being deteriorated by the physical characteristics of the diaphragm, and to form a better acoustic environment with higher output.

  According to the invention described in claim 5, the loudspeaker includes a sound generator that outputs an audible sound to the air based on an audible band signal, and the first ultrasonic generator around the sound generator; By arranging the second ultrasonic generator, it is possible to propagate the audible sound generated by the sound generator and the ultrasonic waves generated by the first and second ultrasonic generators in the same direction. Thereby, the listener who exists in the propagation direction of an audible sound and an ultrasonic wave can be made to hear the audio | voice as a difference sound of an audible sound and both ultrasonic waves. Thereby, since the sound field formed by the sound as the difference sound of the ultrasonic wave is complemented by the sound field formed by the audible sound, it is possible to form an acoustic environment having a natural sense of presence with a depth. .

  Embodiments for carrying out the present invention will be described below.

FIG. 1 is a schematic diagram showing the overall configuration of the ultrasonic speaker system of this embodiment. As shown in the figure, the ultrasonic speaker system 1A includes an audio input unit 1, an oscillation unit (oscillation unit) 2, a frequency modulation unit (frequency modulation unit) 3, and amplification units 4 ₁ , 4 ₂ , 4 ₃ and , Audible sound speaker (sound generator) 5, M (M ≧ 1) first ultrasonic speakers (first ultrasonic generator) 6 _{1 to} 6 _m , N (N ≧ 1) second super And a loudspeaker 8 (sounding means) having sound wave speakers (second ultrasonic generators) 7 _{1 to} 7 _n .

Audio input unit 1 is provided with an input jack, and performs processing necessary for receiving the supply of the audio signal s _1.

Oscillator 2 is like LC oscillator, crystal oscillator, and outputs a carrier signal s ₂ is a signal of a specific frequency of the ultrasonic band.

Frequency modulation unit 3, a variable capacitance diode or the like, performs frequency modulation by the audio signal supplied a carrier signal supplied from the audio input unit 1 from the oscillator 2, the modulated signal s ₃ obtained as a result of modulation Output.

The amplification units 4 ₁ , 4 ₂ , 4 ₃ are amplification circuits including FETs and the like, amplify the input electric signal and output it.

  The audible sound speaker 5 is a high-performance ultra-small speaker, has a substantially hemispherical diaphragm 5a having a diameter of about 3 centimeters, and has very good reproduction characteristics in an audible frequency band of about 20 Hz to 20 kHz. As long as the audible sound speaker 5 is small and has a very good reproduction characteristic in the audible frequency band, any conversion system such as an electrodynamic type, an electrostatic type, and a piezoelectric type may be used.

The first ultrasonic speakers 6 _{1 to} 6 _m and the second ultrasonic speakers 7 _{1 to} 7 _n are speakers having good reproduction characteristics in an ultrasonic region higher than 20 kHz. Specific configurations of the first ultrasonic speakers 6 _{1 to} 6 _m and the second ultrasonic speakers 7 _{1 to} 7 _n will be described later.

FIG. 2 is a schematic view of the loudspeaker 8 in the ultrasonic speaker system 1A of this embodiment as viewed from the front. As shown in the figure, the loudspeaker 8 is disposed in the center of the front surface of the substrate 9 formed in a substantially disc shape with the audible sound speaker 5 being fixed with the diaphragm 5a facing the front. A plurality of bottomed cylindrical first ultrasonic speakers 6 _{1 to} 6 _m and a plurality of bottomed cylindrical second ultrasonic speakers 7 _{1 to} 7 _n vibrate around the audible sound speaker 5. The plates 15 are densely arranged with the front facing. Lead wires (not shown in FIG. 2) for conducting electrical signals are drawn out from the bottom surfaces of the audible sound speaker 5, the first ultrasonic speakers 6 _{1 to} 6 _m and the second ultrasonic speakers 7 _{1 to} 7 _n , respectively. These lead wires (not shown in FIG. 2) are arranged so as to converge on the front surface of the substrate 9 toward the central portion of the substrate 9 and are connected to the lead wires 10 on the back surface of the audible speaker 5. They are connected (the arrangement state of the lead wires and the connection state between the lead wires 10 are not shown in FIG. 2). A conducting wire 10 is drawn out from a substantially central part on the back side of the substrate 9 and connected to the amplifying parts 4 ₁ , 4 ₂ , 4 ₃ (FIG. 1).

FIG. 3 is a schematic view of the loudspeaker unit 8 in the ultrasonic speaker system 1A according to this embodiment as viewed from the side. FIG. 3 schematically shows the state of transmission of the loudspeaker unit 8 in addition to the configuration of the loudspeaker unit 8. It shows. As shown in the figure, a hole 9a is formed through the substantially central portion of the substrate 9 from the front side (right side in FIG. 3) to the back side (left side in FIG. 3). Lead wires (not shown in FIG. 3) drawn from the listening speaker 5, the first ultrasonic speakers 6 _{1 to} 6 _m and the second ultrasonic speakers 7 _{1 to} 7 _n are connected to the conductive wire 10. Is drawn out to the back side of the substrate 9 through the hole 9a.

Further, as shown in FIG. 3, the central axis 11a of the propagation of the sound output from the audible speaker 5 (that is, a virtual line drawn from the center of the back surface of the diaphragm 5a toward the center of the front surface of the diaphragm 5a) is The first ultrasonic speakers 6 _{1 to} 6 _m and the second ultrasonic speakers 7 _{1 to} 7 _n are parallel to the propagation direction of ultrasonic waves (that is, the direction perpendicular to the diaphragm 15 on the front side) 11b. 2 and 3, since the first ultrasonic speakers 6 _{1 to} 6 _m and the second ultrasonic speakers 7 _{1 to} 7 _n have the same configuration, hereinafter, the first ultrasonic speaker 6 and the second ultrasonic speaker will be described. The sound wave speaker 7 is used.

  FIG. 4 is a schematic diagram showing a cross-sectional side view of the periphery of the diaphragm of the second ultrasonic speaker 7 in the ultrasonic speaker system 1A of this embodiment. As shown in the figure, the second ultrasonic speaker 7 has a substantially bottomed cylindrical main body portion 11 in which a substantially cylindrical side portion 12 is provided on the periphery of a substantially disc-shaped bottom plate portion 16. Yes. A disc-shaped diaphragm holding portion 13 protrudes from a part of the inner peripheral portion of the side portion 12 in a direction substantially orthogonal to the side portion 12. A substantially circular opening 14 is formed. The main body 11 is formed of a material that can be easily processed and has high plasticity, such as wood, aluminum, and steel.

  A substantially disc-shaped diaphragm 15 is fixed to the inner periphery of the opening 14. The diaphragm 15 has a small mass, has high rigidity and moderate elasticity, can be easily processed into a plate shape, and is formed of a material that generates a large eddy current when placed in a high-frequency magnetic field. . In this embodiment, the diaphragm 15 is made of metal such as duralumin.

  A drive unit 17 that vibrates the diaphragm 15 is disposed in a space formed between the bottom plate part 16 and the diaphragm 15 on the inner periphery of the main body 11. The drive unit 17 includes a magnet 18, a pole piece 19, an outer peripheral coil 20a, and an inner peripheral coil 20b.

  The magnet 18 is substantially disk-shaped and is disposed substantially parallel to the bottom plate portion 16. The magnet 18 is a permanent magnet formed of a material having high coercive force such as alnico, ferrite, neodymium, and the like, and one side is an N pole and the other side is an S pole. The magnet 18 may be formed of an electromagnet, a superconducting material, or the like that can control the magnitude of the magnetic force or generate a higher magnetic force.

  A substantially cylindrical pole piece 19 is disposed on the periphery of the magnet 18 with the open end facing the bottom plate portion 16 and the diaphragm 15, and one end side of this pole piece 19 (the lower side in FIG. 4). Are joined to the peripheral edge of the magnet 18, respectively. The pole piece 19 is made of a soft magnetic material having high magnetic permeability such as soft iron or permalloy. The other end surface 21 formed at the other end portion (upper side in FIG. 4) of the pole piece 19 is opposed to the diaphragm 15 in a state of being close to the diaphragm 15, and the gap portion 22 is provided between the other end surface 21 and the diaphragm 15. Is provided. The gap 22 is configured so that the magnetic force generated by the drive unit 17 is transmitted to the diaphragm 15 well, and when the diaphragm 15 vibrates in the vertical direction (vertical direction in FIG. 4), the diaphragm and the other end surface 21 The diaphragm 15 and the other end surface 21 are formed so as to be spaced apart from each other so that they do not contact each other.

The outer periphery side coil 20a and the inner periphery side coil 20b are each formed in a substantially annular shape and are accommodated in a substantially annular outer covering portion 23a and an inner covering portion 23b formed in an approximately U-shaped cross section by an insulating material. The pole piece 19 is disposed on the outer peripheral portion and the inner peripheral portion in the vicinity of the other end portion. That is, the outer peripheral side coil 20a and the inner peripheral side coil 20b are covered with the covering portions 23a and 23b on the surface facing the pole piece 19, the diaphragm 15 side, and the bottom plate portion 16 side. One end portions of the outer peripheral side coil 20a and the inner peripheral side coil 20b are electrically connected to each other by a conductive portion 24 formed of a coated copper wire, and the outer peripheral side coil 20a and the inner peripheral side coil 20b are respectively connected to the lead wires 25a and 25b. It is connected to one end side. The lead wires 25a and 25b are small-diameter copper wires or the like, and are led out of the main body 11 from a hole 26 formed through a part of the bottom plate 16 of the main body 11, and the other end is on the amplifying unit 4 _It is connected to one of _two positive terminals and a negative terminal (not shown).

  In this embodiment, the first ultrasonic speaker 6 has the same configuration as the second ultrasonic speaker 7.

  Next, the operation of this embodiment will be described.

As shown in FIG. 1, in the ultrasonic speaker system 1A, the oscillation unit 2 oscillates steadily, and outputs a signal having a predetermined frequency f ₂ (where f ₂ is an ultrasonic band higher than the audible band) as the carrier signal s ₂ . . The carrier signal s ₂ is transmitted to the first ultrasonic speaker 6 through the frequency modulation unit 3, and the amplifying unit 4 _3.

Here, the voice signal s ₁ of the frequency f _{1 (provided} that f ₁ is audio band) is supplied to the ultrasonic speaker system 1A from an audio amplifier (not shown) or the like, audio input of the audio signal s ₁ part 1 is received, an audible tone speaker 5 via the amplifier section 4 _1, and transmits the frequency modulator 3.

The frequency modulation unit 3 performs frequency modulation on the audio signal s ₁ using the carrier signal s ₂ to form a signal having a frequency f ₁ + f ₂ . Frequency modulation unit 3, a frequency _f 1 + _{f 2} of the modulated signal _{s 3} which is formed and transmitted to the second ultrasonic speaker 7 via the amplifier section _{4 2.} Modulated signal s ₃ is for those obtained by frequency modulating the original speech signal s _1, faithfully depend on the nature of the speech signal s _1, it can be formed as a high signal reproducibility and gain.

When the modulation signal s ₃ (or the carrier signal s ₂ ) is received by the second ultrasonic speaker 7 (and the first ultrasonic speaker 6), the signal is transmitted from the lead wire 25a (or the lead wire 25b) to the outer periphery as shown in FIG. The coil is supplied to the inner coil 20b (or outer coil 20a) via the side coil 20a (or inner coil 20b) and the conductive portion 24.

The magnetic flux generated by the magnet 18 is guided to the pole piece 19 to form a magnetic field around the other end surface 21, but a signal is conducted to the outer peripheral side coil 20 a and the inner peripheral side coil 20 b and the outer peripheral side coil 20 a, When a magnetic field is formed around the inner periphery side coil 20b, the magnetic field generated by the magnet 18 changes. Due to this change, an eddy current is generated on the surface of the diaphragm 15 in a direction orthogonal to the direction of the magnetic field. A Lorentz force is generated in the orthogonal direction for both the direction of the eddy current and the direction of the magnetic field. When the magnitude and direction of the current flowing in the outer peripheral coil 20a and the inner peripheral coil 20b change, the direction of the magnetic field and the magnitude and direction of the eddy current change and invert, respectively, thereby changing the magnitude and direction of the Lorentz force. Invert. Thereby, when the modulation signal s ₃ (or the carrier signal s ₂ ) is input to the outer peripheral coil 20a and the inner peripheral coil 20b, the Lorentz force generated in the diaphragm 15 changes with the change of the signal, the diaphragm 15 is vibrated with a change (see FIG. 2), the modulated signal s ₃ and carrier signal s ₂ propagates is converted into air vibrations in the air.

The carrier signal s ₂ and the modulation signal s ₃ are high-frequency currents that easily generate eddy currents, and the signals s ₂ and s _{3 are} generated by vibrating the diaphragm 15 by the Lorentz force generated by the signals s ₂ and s ₃ . The vibration can be efficiently conducted to the diaphragm 15. Thereby, the reproducibility and gain of the sound heard as a difference sound can be improved, and a better acoustic environment with higher output can be formed.

  In addition, since the diaphragm 15 is made of a lightweight and highly rigid metal (duralumin), even if the diaphragm 15 is vibrated at high speed due to an ultrasonic band signal, the diaphragm 15 is unlikely to be physically distorted. In addition, since the gap 22 is provided between the diaphragm 15 and the other end surface 21 and the diaphragm 15 and the drive unit 17 are separated from each other, the vibration of the diaphragm 15 is not hindered by the drive unit 17. . Therefore, the diaphragm 15 vibrates without causing distortion even if it is a high-speed vibration in the ultrasonic band.

  In the first ultrasonic speaker 6 and the second ultrasonic speaker 7, the diaphragm 15 faces the front direction of the substrate 9, and this direction is a propagation direction of ultrasonic waves 11 b and 11 b (from the respective ultrasonic speakers 6 and 7). Fig. 3). Therefore, ultrasonic waves emitted from both the first ultrasonic speaker 6 and the second ultrasonic speaker 7 propagate to the eardrum of the listener in the propagation directions 11b and 11b.

  Here, FIG. 5 is a schematic diagram showing the relationship between the ultrasonic wave generated by the first ultrasonic speaker 6 and the second ultrasonic speaker 7 and the difference tone (Difference Tone) in the ultrasonic speaker system 1A of this embodiment. The figure is shown. As shown in the figure, when ultrasonic waves with different frequencies are output from multiple speakers (however, the frequency difference between the ultrasonic waves is the frequency of the audible band), the eardrum of the listener who listened to these ultrasonic waves simultaneously The sound having a frequency corresponding to the frequency difference between the ultrasonic waves is heard. For example, as shown in the figure, when an ultrasonic wave 100 having a specific frequency (80 kHz in this case) is output from one speaker and an ultrasonic wave 101 having another specific frequency (here 81 kHz) is simultaneously output from another speaker, An audible sound 102 having a frequency difference between the ultrasonic waves 100 and 101 (here, 1 kHz) is heard on the eardrum of the listener who has listened to both ultrasonic waves 100 and 101 at the same time. If the frequency difference between the two ultrasonic waves 100 and 101 is continuously changed, it is possible to make the listener listen to the sound that continuously changes in accordance with the frequency difference. In the ultrasonic speaker system 1A of this embodiment, this principle is applied to make the listener listen to the sound.

Specifically, an ultrasonic wave having a frequency f ₂ based on the carrier signal s ₁ is output from the first ultrasonic speaker 6, and an ultrasonic wave having a frequency f ₁ + f ₂ based on the modulation signal s ₃ is output from the second ultrasonic speaker 7. When output, the eardrum of the listener who has listened to the ultrasonic waves emitted from the ultrasonic speakers 6 and 7 at the same time hears the sound of the frequency difference f ₁ , that is, the sound based on the sound signal s ₁ . Carrier frequency of the signal s ₃ is constant, the frequency of the modulation signal s ₃ fluctuates constantly depending on the frequency f ₁ of the speech signal s _1, the eardrum of the listener, changes in the speech signal s ₁ Will be heard.

Then, as shown in FIGS. 2 and 3, the center substrate 9 of the loudspeaker unit 8 is disposed an audible sound speaker 5 outputs a sound based on the audio signal s _1. When an ultrasonic wave is generated from the first ultrasonic speaker 6 and the second ultrasonic speaker 7 and a sound is generated from the audible sound speaker 5, the sound wave generated from the audible sound speaker 5 is the first ultrasonic speaker 6, 2 Propagates to the air surrounded by the ultrasonic waves generated from the ultrasonic speaker 7. Then, in the propagation direction 11b and the central axis 11a direction of the ultrasonic waves generated from the first ultrasonic speaker 6 and the second ultrasonic speaker 7, the audio wave of the audible sound generated from the audible sound speaker 5 and the first supersonic wave. The sound field formed by the audible sound speaker 5, the first ultrasonic speaker 6, and the second ultrasonic speaker are interacted with ultrasonic waves with high linearity generated from the sound wave speaker 6 and the second ultrasonic speaker 7. The sound field generated by 7 merges. The sound field is generated by generating sound from the audible sound speaker 5 that can output sound without impairing the frequency characteristics of the original sound, and the sound field formed by the first ultrasonic speaker 6 and the second ultrasonic speaker 7 By merging, the sound field formed by the first ultrasonic speaker 6 and the second ultrasonic speaker 7 is complemented, and an acoustic environment having a natural sense of presence with a deep depth can be formed.

As shown above, in the ultrasonic speaker system 1A of this embodiment, it is possible to listen to high output of the sound reproduced with the original speech signal s ₁ high quality to a listener, high output, good An acoustic environment can be formed.

  In the above embodiment, the diaphragms 15 of the first ultrasonic speaker 6 and the second ultrasonic speaker 7 are made of metal, for example, duralumin. However, the present invention is not limited to this, and the mass is small, high rigidity, and appropriate elasticity. As long as it is a material that can be easily processed into a plate shape and generates a large amount of eddy current when placed in a high-frequency magnetic field, any metal other than duralumin and any material other than metal You may form the diaphragm 15 using.

  In the above embodiment, the oscillation unit 2, the frequency modulation unit 3 and the like are formed by electronic circuits such as a coil, a capacitor, and a transistor, and oscillation and modulation are performed according to the characteristics of each element. However, the present invention is not limited to this. The oscillation and modulation may be controlled using a CPU or the like.

  In the above embodiment, the loudspeaker 8 is arranged with the audible speaker 5, the first ultrasonic speaker 6, and the second ultrasonic speaker 7 on the front surface of the substrate 9 with the diaphragms 5a and 15 facing the front, respectively. The first ultrasonic speaker 6 and the second ultrasonic speaker 7 are fixedly disposed on the front surface of the substrate 9 and the audible sound speaker 5 is fixedly disposed on the rear surface. The sound output from the audible sound speaker 5 can be reflected on the inner surface of the reverberation plate and propagated in the front direction of the substrate 9. By directing the sound output from the audible sound speaker 5 to the inner surface of the rotating hyperboloid-shaped reverberation plate, the directivity of the sound output from the audible sound speaker 5 can be increased and propagated.

In the above embodiment, comprises a frequency modulator 3 in the ultrasonic speaker system 1A, it has formed the modulated signal _{s 3} by the frequency modulation, pulse width modulation instead of frequency modulation unit 3 (PWM: Pulse Width Modulation) method The audio signal s ₁ may be PWM-modulated, sent to the second ultrasonic speaker 7 and output, and a difference sound from the ultrasonic wave output from the first ultrasonic speaker 6 may be formed. . By using a pulse width modulation method that can be realized with a relatively simple circuit configuration for forming a modulation signal, the ultrasonic speaker system 1A can be realized with a simple circuit configuration, thereby simplifying the manufacturing process and reducing costs. it can.

  The above embodiment is an exemplification of the present invention, and it is needless to say that the present invention is not limited to the above embodiment.

  As described above, the ultrasonic speaker system of the present invention has excellent sound image localization, excellent reproducibility of a wide-range feeling of the sound field, and can realize a speaker system with a directional ultrasonic parallel beam. In addition, as a spot audio service business, product explanation and advertisement in commercial facilities such as shops, department stores, supermarkets, explanation of exhibitions at cultural amusement facilities such as halls, drive-in theaters, museums, and zoos, and public facilities such as station buildings and roads It can be applied to providing alerting information at facilities, and can also be applied to hi-fi speakers for reproducing acoustic characteristics and loudspeakers for public broadcasting.

It is the schematic which shows the whole structure of the ultrasonic speaker system of this embodiment. It is the schematic diagram which looked at the loudspeaker part in an ultrasonic speaker system same as the above from the front. It is the schematic diagram which looked at the loud sound part in the ultrasonic speaker system same as the above from the side. It is a schematic diagram which shows the side surface cross section of the diaphragm periphery of a 2nd ultrasonic speaker in an ultrasonic speaker system same as the above. It is a schematic diagram showing the relationship between the ultrasonic wave which a 1st ultrasonic speaker and a 2nd ultrasonic speaker generate | occur | produce, and a difference sound (Difference Tone) in an ultrasonic speaker system same as the above.

Explanation of symbols

1A ... ultrasonic speaker system 2 ... oscillating unit 3, ... the frequency modulation unit 5 ... audible sound speaker 6,6 ₁ to 6 _m ... first ultrasonic speaker 7, 7 ₁ to _7-n ... 2nd ultrasonic speaker 8 ... Loudspeaker 15 ... Diaphragm 17 ... Drive part 22 ... Gap part 100 ... Ultrasound 101 ... Ultrasound s ₁ ... Voice Signal s ₂ ... carrier signal s ₃ ... modulation signal

Claims (5)

First ultrasonic output means for outputting an ultrasonic band signal;
Second ultrasonic output means for receiving an audio signal of an audible band and outputting an ultrasonic band signal whose frequency band is continuously changed depending on the audio signal;
A first ultrasonic generator that outputs an ultrasonic wave according to the signal output from the first ultrasonic output means, and a first ultrasonic wave that outputs an ultrasonic wave according to the signal output from the second ultrasonic output means. An ultrasonic speaker system comprising: a loudspeaker means including two ultrasonic generators. The first ultrasonic output means is an oscillating means for generating an ultrasonic band signal;
The second ultrasonic wave output means is a frequency modulation means for frequency-modulating the ultrasonic band signal with the audio signal and outputting a modulation signal obtained by the frequency modulation,
2. The ultrasonic speaker system according to claim 1, further comprising: a driving unit configured to vibrate the diaphragm by Lorentz force in at least the second ultrasonic generator of the two ultrasonic generators.   The ultrasonic speaker system according to claim 1, wherein the ultrasonic generator including the driving unit includes a gap between the diaphragm and the driving unit.   The ultrasonic speaker system according to claim 1, wherein the diaphragm is made of metal. The loudspeaker includes a sound generator that outputs an audible sound to the air based on an audible band signal, and the first ultrasonic generator and the second ultrasonic generator around the sound generator. The ultrasonic speaker system according to claim 1, wherein the ultrasonic speaker system is provided.

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