JP2012239023A - Parametric speaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a parametric speaker capable of promoting demodulation of a low-tone sound thereby attaining a sound gentle on human ears, with high efficiency, and with a removed low-tone sound shortage.SOLUTION: An ultrasonic wave generation part 4 of a parametric speaker 1 emits ultrasonic wave towards a film member 3, which is stretched on an opening 2a of a housing 2 with tension applied thereto, and the ultrasonic wave reflected by the film member 3 is emitted in a target direction. Most of the ultrasonic wave reflected by the film member 3 with tension applied thereto is emitted in the target direction without being attenuated. A part of the ultrasonic wave of the ultrasonic wave reflected by the film member 3 oscillates the film member 3. Since the film member 3 is oscillated while receiving air viscosity, a low-tone sound being delayed in demodulation is forcedly demodulated by the oscillation of the film member 3. Consequently, there is provided a sound gentle on human ears, with high efficiency, and with a removed low-tone sound shortage.

Description

The present invention generates an ultrasonic wave obtained by ultrasonically modulating an audible sound from an ultrasonic wave generator (specifically, an ultrasonic wave generator that generates ultrasonic waves in an ultrasonic speaker), and is separated from the ultrasonic wave generator. It relates to a parametric speaker in which audible sound is reproduced in the air, for example,
(I) a vehicle presence notification device that notifies the surroundings of the presence of the vehicle by a notification sound;
(Ii) a warning device that informs the driver by a notification sound that the vehicle is in a driving state where the vehicle starts when the accelerator is depressed;
(Iii) an audio device for providing audio sounds such as music and radio sound to a plurality of passengers boarding the vehicle;
(Iv) a personal audio device for providing audio sound only to a specific vehicle occupant;
The present invention relates to a technique suitable for use.

  Waveform signal (electric signal) of audible sound is ultrasonically modulated and irradiated into the air from the ultrasonic generator, and the modulation component contained in the ultrasonic wave (sound that cannot be heard by the ear) is self-demodulated in the air that is being propagated. Thus, there is known a parametric speaker that generates an audible sound (notification sound) at a location away from the ultrasonic wave generation unit.

Since this parametric speaker is a technology that uses ultrasonic waves with strong directivity (straightness), audible sound can be generated only in an arbitrary direction.
For this reason, a notification sound (such as a pseudo engine sound) can be generated only in a specific direction of the vehicle (such as forward), which is suitable for use in a vehicle presence notification device.
Alternatively, a warning sound (sound or the like) can be generated only for the driver among the occupants of the vehicle, which is suitable for use in a device for alerting the driver.
Furthermore, audio sound (music, radio sound, etc.) can be given to a plurality of occupants, or audio sound can be generated only for a specific occupant among a plurality of occupants. It is suitable for use in an apparatus.

  However, since the parametric loudspeaker self-demodulates the ultrasonic wave using the viscosity (non-linearity) of air, it is necessary to move away from the ultrasonic wave generation unit in order to self-demodulate as the frequency is lower. That is, at a distance close to the ultrasonic wave generation unit, the degree of demodulation of the bass is small and the bass is small.

As a technique for solving the above problems, a technique disclosed in Patent Document 1 is known.
The technique of Patent Document 1 uses the fact that the bass is small when the distance between the ultrasonic generators is short, but the treble that is quickly demodulated becomes large, and the high frequency side is actively attenuated to flatten the frequency ( This is a technique for reproducing the original sound that brings the timbre close to the input signal.
Specifically, the technique of Patent Document 1 is to reflect an ultrasonic wave radiated from an ultrasonic wave generation unit toward a person with a reflector having a sound wave attenuating function, and actively reflects the high-pitched side in the reflector. This is a technique for flattening the frequency by attenuation.

However, since the technology of Patent Document 1 is a technology for flattening the frequency by attenuating the high sound side with a reflector and adjusting the sound pressure on the high sound side to the low sound side, the sound pressure reaching the human ear is Naturally it will be small.
In order to return the sound pressure reaching the human ear before attenuation, it is necessary to increase the sound pressure of the ultrasonic wave radiated from the ultrasonic wave generation unit. For this reason, the technique of Patent Document 1 consumes a large amount of power and is inefficient.
In addition, since the technique of Patent Document 1 needs to increase the sound pressure generated by ultrasonic waves, when a problem occurs in the reflector due to some factor, ultrasonic waves that do not attenuate (high sound pressure ultrasonic waves) are generated by the human ear. There is a concern that it may have an adverse effect on the ear.

JP 2003-163986 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a parametric speaker that promotes demodulation of bass sounds, is gentle to human ears, is efficient, and can solve the shortage of bass sounds. .

[Means of Claim 1]
The parametric speaker according to claim 1 is configured to reflect the ultrasonic wave irradiated from the ultrasonic wave generation unit with a film member (film body stretched in a state where tension is applied), and to a target direction (with respect to the ultrasonic wave generation unit). An ultrasonic wave reflected in an arbitrary reflection direction depending on the inclination angle of the film member is directed.
Since ultrasonic waves have high straightness and excellent reflectivity, most of the ultrasonic waves reflected by the film member to which tension is applied are radiated in the target direction without being attenuated by the film member.

  On the other hand, some of the ultrasonic waves hitting the membrane member vibrate the membrane member. Since the membrane member vibrates while receiving the viscosity (nonlinearity) of air, the modulation component of the ultrasonic wave that vibrates the membrane member is demodulated into an audible sound by the vibration of the membrane member. As a result, a low frequency component that is delayed in demodulation can be generated by vibration of the membrane member.

As described above, since most of the ultrasonic waves are reflected by the film member without being attenuated by the film member and are emitted in the target direction, the efficiency is not deteriorated.
Moreover, since the lack of bass is compensated by demodulation by vibration of the membrane member, the lack of bass can be solved.
Furthermore, since there is no need to increase the sound pressure of the ultrasonic waves as in the prior art, there is no problem that the ultrasonic waves with the increased sound pressure reach the human ear.
That is, the parametric speaker according to claim 1 promotes demodulation of bass, is gentle to human ears, is efficient, and can solve the shortage of bass.

[Means of claim 2]
The parametric speaker according to claim 2 irradiates the membrane member with ultrasonic waves emitted from the ultrasonic wave generation unit, and a part (including a majority) of the ultrasonic waves generated by the ultrasonic wave generation unit is applied to the film member. It passes through the provided ultrasonic passage hole and is radiated in a target direction (an arbitrary direction in which the ultrasonic wave generator is directed).

  On the other hand, some of the ultrasonic waves hitting the membrane member vibrate the membrane member. Since the membrane member vibrates while receiving the viscosity (nonlinearity) of air, the modulation component of the ultrasonic wave that vibrates the membrane member is demodulated into an audible sound by the vibration of the membrane member. As a result, a low frequency component that is delayed in demodulation can be generated by vibration of the membrane member.

In this way, a part of the ultrasonic wave passes through the ultrasonic wave passage hole and is emitted in the target direction, so that the efficiency is not deteriorated.
Moreover, since the lack of bass is compensated by demodulation by vibration of the membrane member, the lack of bass can be solved.
Furthermore, since there is no need to increase the sound pressure of the ultrasonic waves as in the prior art, there is no problem that the ultrasonic waves with the increased sound pressure reach the human ear.
That is, the parametric loudspeaker according to the second aspect, like the means of the first aspect, promotes the demodulation of the bass, is gentle to the human ear, is efficient, and can solve the shortage of the bass.

[Means of claim 3]
According to a third aspect of the present invention, the membrane member is provided in an opening of a housing (container) in which a volume chamber is formed.
Since the air in the volume chamber exerts a dumping action (an action for increasing non-linearity) for damping the vibration of the membrane member, the demodulation efficiency due to the vibration of the membrane member can be increased.

[Means of claim 4]
The volume chamber of claim 4 forms a closed space.
When the volume chamber forms a closed space, it is possible to enhance the dumping action for damping the vibration of the membrane member, and to further improve the demodulation efficiency due to the vibration of the membrane member.

[Means of claim 5]
The parametric speaker according to claim 5 is used in a vehicle presence notification device that generates a notification sound outside the vehicle to notify the presence of the vehicle.
For this reason, it is possible to solve the shortage of the reproduced sound of the parametric speaker near the vehicle.

It is explanatory drawing of the parametric speaker which reflects an ultrasonic wave with a film | membrane member (Embodiment 1). It is explanatory drawing of the parametric speaker which applies a ultrasonic wave to a film | membrane member and allows some ultrasonic waves to pass through (Embodiment 2). FIG. 3 is a vehicle mounting diagram of an ultrasonic speaker and a vehicle horn (Example 1). (Example 1) which is a top view of a film | membrane member. 1 is a schematic diagram of a vehicle presence notification device (Example 1). (Example 1) which is a principle explanatory drawing of a parametric speaker.

[Embodiment 1]
The first embodiment will be described with reference to FIG.
The parametric speaker 1 of Embodiment 1 is
A membrane member 3 stretched in a state where tension is applied to the opening 2a of the housing 2 in which a volume chamber is formed;
An ultrasonic generator 4 that is disposed outside the housing 2 and converts an ultrasonic signal (electrical signal) into an ultrasonic wave (dense wave of air) and irradiates the ultrasonic wave toward the membrane member 3;
An ultrasonic modulation means 5 for generating an ultrasonic signal obtained by ultrasonically modulating an audible sound signal;
An ultrasonic driving means (amplifying means) 6 for driving the ultrasonic generator 4 by the ultrasonic signal generated by the ultrasonic modulation means 5;
Comprising
The ultrasonic wave reflected by the film member 3 is irradiated in the air (target direction: for example, in front of the vehicle).

Most of the ultrasonic waves reflected by the film member 3 to which tension is applied are radiated toward the target direction without being attenuated by the film member 3.
On the other hand, some ultrasonic waves (ultrasonic waves related to the natural frequency of the film member 3) among the ultrasonic waves hitting the film member 3 vibrate the film member 3. At that time, since the membrane member 3 vibrates due to the viscosity of the air, the modulation component of the ultrasonic wave that vibrates the membrane member 3 is demodulated into an audible sound. Thereby, a low frequency component that is delayed in demodulation can be generated by vibration of the membrane member 3.

As described above, since most of the ultrasonic waves are reflected by the film member 3 without being attenuated and are emitted in the target direction, the efficiency is not deteriorated.
Further, the lack of bass can be compensated for by the demodulation of the bass due to the vibration of the membrane member 3.
Furthermore, since there is no need to increase the sound pressure of the ultrasonic waves as in the prior art, there is no problem that the ultrasonic waves with the increased sound pressure reach the human ear.
In other words, the parametric speaker 1 according to the first embodiment promotes the demodulation of bass, is gentle to human ears, is efficient, and can solve the shortage of bass.

[Embodiment 2]
A second embodiment will be described with reference to FIG.
The parametric speaker 1 of Embodiment 2 is
A membrane member 3 stretched in a state where tension is applied to the opening 2a of the housing 2 in which a volume chamber is formed;
An ultrasonic generator 4 that is disposed inside the housing 2, converts an ultrasonic signal (electrical signal) into an ultrasonic wave (dense wave of air), and irradiates the ultrasonic wave toward the membrane member 3;
An ultrasonic modulation means 5 for generating an ultrasonic signal obtained by ultrasonically modulating an audible sound signal;
An ultrasonic driving means (amplifying means) 6 for driving the ultrasonic generator 4 by the ultrasonic signal generated by the ultrasonic modulation means 5;
It comprises.
The membrane member 3 includes an ultrasonic wave passage hole 3a that allows a part (including a majority) of ultrasonic waves generated by the ultrasonic wave generation unit 4 to pass therethrough, and the ultrasonic wave that has passed through the ultrasonic wave passage hole 3a is transmitted in the air. (Target direction: for example, in front of the vehicle).

The ultrasonic wave that has passed through the ultrasonic wave passing hole 3 a is radiated in the target direction without being attenuated by the membrane member 3.
On the other hand, some ultrasonic waves (ultrasonic waves related to the natural frequency of the film member 3) among the ultrasonic waves hitting the film member 3 vibrate the film member 3. Since the membrane member 3 vibrates while receiving the viscosity (non-linearity) of air, the modulation component of the ultrasonic wave that vibrates the membrane member 3 is demodulated into an audible sound by the vibration of the membrane member 3. Thereby, a low frequency component that is delayed in demodulation can be generated by vibration of the membrane member 3.

As described above, since a part of the ultrasonic wave is radiated in the target direction through the ultrasonic wave passage hole 3a, the efficiency is not deteriorated.
Further, the lack of bass can be compensated for by the demodulation of the bass due to the vibration of the membrane member 3.
Furthermore, since there is no need to increase the sound pressure of the ultrasonic waves as in the prior art, there is no problem that the ultrasonic waves with the increased sound pressure reach the human ear.
In other words, the parametric speaker 1 according to the second embodiment promotes demodulation of bass, is gentle to human ears, is efficient, and can solve the shortage of bass.

Hereinafter, a specific example (example) to which the present invention is applied will be described with reference to the drawings. The embodiment described below is a specific example, and it goes without saying that the present invention is not limited to the embodiment.
In the following examples, the same reference numerals as those in the “DETAILED DESCRIPTION OF THE INVENTION” denote the same functional objects.

[Example 1]
Embodiment 1 will be described with reference to FIGS.
In this example, the second embodiment described above is applied to a parametric speaker 1 mounted on a vehicle presence notification device, and details thereof will be described below.

  The vehicle presence notification device notifies the presence of a vehicle by a notification sound (for example, pseudo engine sound: not limited), for example, a vehicle (electric vehicle, fuel cell vehicle) not equipped with an engine (internal combustion engine). Etc.), vehicles that may stop the engine while traveling and stopped (hybrid vehicles, etc.), vehicles that may stop the engine while stopped (such as idle stop vehicles), or engine vehicles It is mounted on a convex vehicle with a quiet running sound.

This vehicle presence notification device
A parametric speaker 1 that emits an ultrasonic wave that is generated by ultrasonically modulating a frequency signal forming a notification sound toward the outside of the vehicle;
A vehicle horn 11 used as a dynamic speaker that emits an audible notification sound directly outside the vehicle;
A control circuit 12 for controlling the operation of the parametric speaker 1 and the vehicle horn 11,
It is configured with.

(Description of parametric speaker 1)
The ultrasonic speaker 7 that generates ultrasonic waves in the parametric speaker 1 generates air vibrations having a frequency (20 kHz or higher) higher than the human audible band, and emits ultrasonic waves toward the front of the vehicle. It is mounted on.
Specifically, the ultrasonic speaker 7 of this embodiment is provided on the front surface of the vehicle horn 11 (the surface facing the front of the vehicle when mounted on the vehicle: for example, a spiral horn). As shown in FIG. 14 and the heat exchanger 15 (a radiator or a heat exchanger for air conditioning, etc.) are attached to the vehicle horn 11 so that the ultrasonic speaker 7 can be connected to the vehicle with the ultrasonic radiation direction directed to the front of the vehicle. Mounted on.

The ultrasonic speaker 7 of this embodiment has at least
An ultrasonic generator 4 that generates ultrasonic waves;
A housing 2 that houses the ultrasonic wave generator 4;
Is provided.

The ultrasonic generator 4 generates an ultrasonic signal (an electric signal having an ultrasonic frequency obtained by ultrasonically modulating an audible sound) provided from the ultrasonic modulator 5 into an ultrasonic wave composed of an air dense wave. The plurality of ultrasonic wave generating elements 16 are configured.
The plurality of ultrasonic wave generating elements 16 are collectively arranged on a support plate 17 fixedly arranged inside the housing 2 and mounted as a speaker array. A specific example of the ultrasonic wave generation element 16 is a small piezoelectric speaker suitable for generation of ultrasonic waves, a piezoelectric element (piezoelectric element) that expands and contracts according to an applied voltage (charge / discharge), and the piezoelectric element. A diaphragm that is driven by expansion and contraction of the element to generate a dense wave in the air is used.

The housing 2 may be provided integrally with a member constituting the vehicle horn 11 or may be provided separately and attached to the vehicle horn 11.
Specifically, the housing 2 is formed with a volume chamber that accommodates the ultrasonic wave generation unit 4 therein, and an opening 2a that emits ultrasonic waves emitted from the respective ultrasonic wave generation elements 16 toward the front of the vehicle. (Ultrasonic radiation port) is provided. The housing 2 is provided in a substantially sealed container except for the opening 2a.

The opening 2a of the housing 2 is provided with waterproof means for preventing rainwater from entering the mounting portion of each ultrasonic wave generating element 16.
As an example of this waterproofing means, in this embodiment, an ultrasonically permeable waterproof sheet 18 covering the opening 2a and a louver 19 disposed on the front surface of the waterproof sheet 18 are provided.

Note that the louver 19 is an armor door (louver) in which rainwater reaches the waterproof sheet 18 as much as possible, and has long and narrow wings arranged horizontally with a gap.
As shown in FIG. 3, the louver 19 is provided with an inclination of approximately 45 ° with respect to the vehicle horizontal direction. As a result, the ultrasonic waves radiated from the respective ultrasonic wave generating elements 16 change the direction downward on the inner surface of the louver 19 and change the direction again on the outer surface of the lower louver 19, resulting in the front of the vehicle. Radiated towards

The opening 2a of the housing 2 is provided with a membrane member 3 that is stretched in a tensioned state.
The membrane member 3 of this embodiment is disposed on the front surface of the waterproof sheet 18 and is provided with a small amount of gap (for example, a gap of about 1 to 5 mm) between the waterproof sheet 18. Unlike FIG. 3, the membrane member 3 may be provided inside the waterproof sheet 18.
The membrane member 3 is a membrane material similar to a percussion membrane (taiko membrane, etc.) of a membrane instrument (taiko, etc.), and is provided by a material (resin membrane, etc.) that has no fluff on the surface and has excellent ultrasonic reflectivity. And has a predetermined natural frequency corresponding to the applied tension, membrane area, and the like.

Further, as shown in FIG. 4, a part of the ultrasonic wave generated by the ultrasonic wave generation unit 4 (for example, 70 to 90% of the ultrasonic wave generated by the ultrasonic wave generation unit 4) is passed through the film member 3. For this purpose, a large number of ultrasonic passage holes 3a are provided.
Although FIG. 4 shows an example in which the ultrasonic passage holes 3a are provided substantially evenly with respect to the membrane member 3, the present invention is not limited thereto, and the arrangement of the ultrasonic passage holes 3a may be biased.
4 shows an example in which a large number of ultrasonic passage holes 3a having the same hole diameter are provided in the membrane member 3, the ultrasonic passage holes 3a having different hole diameters may be provided in the membrane member 3. Alternatively, as another specific example of the ultrasonic wave passing hole 3a, one or more large holes may be provided.

(Description of vehicle horn 11)
As described above, the vehicle horn 11 is fixedly disposed between the front grille 14 and the heat exchanger 15, and provides an alarm when a horn switch (for example, a steering horn button) is operated by an occupant. It is an electromagnetic horn with a known structure that generates sound.
The vehicle horn 11 is mounted on the vehicle such that the opening of the spiral horn faces downward (road surface) so that the notification sound generated from the vehicle horn 11 reaches the vehicle substantially uniformly. It is.

(Description of the control circuit 12)
The control circuit 12 is configured by using a microcomputer chip 21 (abbreviation of a micro computer chip) as shown in FIG. 3. For example, as shown in FIG. Arranged inside (specifically, inside the horn housing) (not limited).

The control circuit 12 will be specifically described with reference to FIG.
The control circuit 12 is connected to a power source (battery) and is supplied with a horn switch signal or a vehicle speed signal (for example, a vehicle speed pulse signal).
(A) determination means 22 for determining “whether the driving state of the vehicle conforms to the condition for generating the notification sound”;
(B) When this determination unit 22 determines that “the driving state of the vehicle is suitable for the generation condition of the notification sound”, the notification sound generation unit 23 that generates the “frequency signal that forms the notification sound”;
(C) an ultrasonic modulation unit 5 that modulates the “frequency signal forming the notification sound” output from the notification sound generation unit 23 into an ultrasonic frequency;
(D) ultrasonic driving means 6 for driving the ultrasonic speaker 7 (a plurality of ultrasonic generating elements 16 constituting the ultrasonic generating section 4);
(E) horn driving means 24 for driving the vehicle horn 11;
Is provided.
Below, each means of said (a)-(e) mounted in the control circuit 12 is demonstrated.

(Description of determination means 22)
For example, when the vehicle speed is a predetermined speed (for example, 20 km / h) or less, the determination unit 22 determines that the driving state of the vehicle is suitable for the generation condition of the notification sound, and sets the notification sound generation unit 23. (It is a specific example for explaining the embodiment and is not limited).

(Description of notification sound generating means 23)
The notification sound generation means 23 is provided by a notification sound generation program (acoustic software). When an operation instruction is given from the determination means 22, a digital signal “frequency signal that makes a notification sound (electric signal of audible frequency: for example, pseudo engine” Electrical signal that makes sound) ”.

(Description of the ultrasonic modulation means 5)
The ultrasonic modulation means 5 ultrasonically modulates the “frequency signal forming the notification sound (an example of an audible sound signal)” output from the notification sound generation means 23.
As a specific example of the ultrasonic modulator 5, in this embodiment, the output signal of the notification sound generator 23 is modulated into a predetermined “amplitude change (voltage increase / decrease change) at an ultrasonic frequency (for example, 25 kHz)”. AM modulation (amplitude modulation) is used.
The ultrasonic modulation means 5 is not limited to AM modulation, but PWM modulation that modulates the output signal of the notification sound generation means 23 to a predetermined “pulse width change (pulse generation time width) at ultrasonic frequency”. Other ultrasonic modulation techniques such as (pulse width modulation) may be used.

A specific example of ultrasonic modulation by the ultrasonic modulation means 5 will be described with reference to FIG.
For example, it is assumed that the “frequency signal forming the notification sound” input to the ultrasonic modulation means 5 is the voltage change shown in FIG. 6A (in the figure, a single-frequency waveform is used for assisting understanding). Showing).
On the other hand, the ultrasonic oscillator mounted on the control circuit 12 is assumed to oscillate at the ultrasonic frequency shown in FIG.

Then, as shown in FIG.
(I) Increasing the amplitude of the voltage due to ultrasonic vibration as the signal voltage of the frequency forming the “frequency signal forming the notification sound” increases,
(Ii) As the signal voltage of the frequency forming the “frequency signal forming the notification sound” decreases, the amplitude of the voltage due to the ultrasonic vibration is decreased.
In this way, the ultrasonic modulation means 5 modulates the “frequency signal forming the notification sound” output from the notification sound generation means 23 to “amplitude change in oscillation voltage” of the ultrasonic frequency.

(Description of ultrasonic driving means 6)
The ultrasonic drive means 6 drives the ultrasonic speaker 7 based on the ultrasonic signal modulated by the ultrasonic modulation means 5 (for example, push-pull class B amplifier or push-pull class D amplifier). By controlling the applied voltage (charging / discharging state) of each ultrasonic generator 16, an ultrasonic wave that modulates a “frequency signal that makes a notification sound” is generated from each ultrasonic generator 16.

(Description of horn driving means 24)
The horn driving means 24 is
(I) While the notification sound generating means 23 is generating the “frequency signal that makes the notification sound”, the vehicle horn 11 is operated as a dynamic speaker, and the “frequency signal that makes the notification sound” is amplified to make the vehicle horn. A power amplifier function for generating an audible notification sound from 11;
(Ii) a continuous ON function that applies a battery voltage to the vehicle horn 11 and generates an alarm sound from the vehicle horn 11 while the horn switch is ON;
Is provided.
Note that “ON of the horn switch” has priority over the “instruction to generate notification sound”, and the horn 11 for the vehicle is always configured to generate an alarm sound when the horn switch is turned ON.

(Operation of vehicle presence notification device)
When the driving state of the vehicle matches the generation condition of the notification sound, the notification sound generation means 23 outputs a “frequency signal that makes a notification sound”, and the ultrasonic speaker 7 displays “notification” as shown in FIG. Ultrasonic waves (inaudible sound waves) obtained by modulating the “frequency signal that makes sound” are emitted toward the front of the vehicle.
Then, as shown in FIG. 6D, as the ultrasonic wave propagates in the air, the ultrasonic wave having a short wavelength is distorted and blunted by the viscosity of the air.
As a result, as shown in FIG. 6E, the amplitude component contained in the ultrasonic wave in the air being propagated is self-demodulated, and as a result, “notification sound” is reproduced in front of the vehicle.
On the other hand, the notification sound generating means 23 outputs a “frequency signal that forms a notification sound”, whereby an audible “notification sound” is directly emitted from the vehicle horn 11 to the surroundings of the vehicle.

(Effect of Example 1)
Part of the ultrasonic waves (many ultrasonic waves) emitted from the ultrasonic wave generation unit 4 (the plurality of ultrasonic wave generation elements 16) passes through the ultrasonic wave passage hole 3a and is emitted toward the front of the vehicle.
On the other hand, some ultrasonic waves 3 (ultrasound directly or indirectly related to the natural frequency of the film member 3) among the ultrasonic waves hitting the film member 3 vibrate the film member 3. Since the membrane member 3 vibrates while receiving the viscosity (non-linearity) of air, the modulation component of the ultrasonic wave that vibrates the membrane member 3 is demodulated into an audible sound by the vibration of the membrane member 3. Thereby, a low frequency component that is delayed in demodulation can be generated by vibration of the membrane member 3.

The demodulated sound of the ultrasonic wave that has passed through the ultrasonic wave passage hole 3a is delayed in the demodulation of the low sound within a range close to the vehicle, and becomes a notification sound with a low low sound.
However, since the parametric speaker 1 of this embodiment compensates for the lack of bass by demodulation by vibration of the membrane member 3, it is possible to eliminate the lack of bass of the notification sound even in a range close to the vehicle. That is, a realistic pseudo engine sound or the like can be generated even near the vehicle.

In this way, a part (many) of the ultrasonic waves pass through the ultrasonic passage hole 3a and are radiated forward of the vehicle, so that it is not necessary to increase the sound pressure of the ultrasonic waves as in the prior art.
In addition, the low-frequency demodulation using the vibration of the membrane member 3 can compensate for the low-frequency lack of the notification sound.
Furthermore, since there is no need to increase the sound pressure of the ultrasonic wave as in the prior art, there is no concern that the ultrasonic wave with the increased sound pressure reaches the human ear.
That is, the parametric speaker 1 mounted on the vehicle presence notification device of this embodiment promotes demodulation of bass, is gentle to human ears, is efficient, and can solve the lack of bass.

In the above-described example, the example in which the second embodiment is applied to the vehicle presence notification device has been described. However, the first embodiment may be applied to the vehicle presence notification device.
That is, an ultrasonic speaker 7 is provided that reflects the ultrasonic wave emitted from the ultrasonic wave generation unit 4 by the film member 3 (film material to which tension is applied so that the ultrasonic wave passage hole 3a is not opened) and directs the ultrasonic wave toward the front of the vehicle. May be mounted on the vehicle.

In the above-described embodiment, an example in which the present invention is applied to the parametric speaker 1 of the vehicle presence notification device has been described.
(I) The parametric speaker 1 is used as a warning device that informs the driver by a notification sound (pseudo engine sound or the like) that the vehicle starts driving when the accelerator is depressed, and the present invention is applied to the parametric speaker 1. Is good,
(Ii) The parametric speaker 1 may be used for an audio device that provides audio sounds such as music and radio sound to a plurality of passengers on the vehicle, and the present invention may be applied to the parametric speaker 1.
(Iii) The parametric speaker 1 may be used in a personal audio device that provides audio sound only to a specific vehicle occupant, and the present invention may be applied to the parametric speaker 1.

DESCRIPTION OF SYMBOLS 1 Parametric speaker 2 Housing 2a Opening part 3 Membrane member 3a Ultrasonic passage hole 4 Ultrasonic wave generation part 5 Ultrasonic modulation means 6 Ultrasonic drive means 7 Ultrasonic speaker

Claims (5)

In a parametric speaker (1) that emits ultrasonic waves obtained by ultrasonically modulating an audible sound signal,
In the parametric speaker (1), an ultrasonic speaker (7) that generates ultrasonic waves irradiates the membrane member (3) stretched in a tensioned state and ultrasonic waves toward the membrane member (3). An ultrasonic generator (4)
A parametric speaker characterized by irradiating in air the ultrasonic wave reflected by the film member (3). In a parametric speaker (1) that emits ultrasonic waves obtained by ultrasonically modulating an audible sound signal,
In the parametric speaker (1), an ultrasonic speaker (7) that generates ultrasonic waves irradiates the membrane member (3) stretched in a tensioned state and ultrasonic waves toward the membrane member (3). An ultrasonic generator (4)
The membrane member (3) includes an ultrasonic wave passage hole (3a) that allows a part of the ultrasonic wave generated by the ultrasonic wave generation unit (4) to pass therethrough, and the ultrasonic wave that has passed through the ultrasonic wave passage hole (3a). A parametric speaker characterized by irradiating air in the air. Parametric speaker (1) according to claim 1 or 2,
The parametric speaker, wherein the membrane member (3) is provided in an opening (2a) of a housing (2) in which a volume chamber is formed. Parametric speaker (1) according to claim 3,
The parametric speaker, wherein the volume chamber in which the membrane member (3) is provided in the opening (2a) forms a closed space. In the parametric speaker (1) according to any one of claims 1 to 4,
The parametric speaker (1) is a parametric speaker that is used in a vehicle presence notification device that generates a notification sound outside a vehicle to notify the presence of the vehicle.

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