JP2012253568A - Acoustic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle presence notification device capable of avoiding increases in size and cost of components while suppressing power consumption.SOLUTION: Inductive speaker driving means 7 is switching means 9 for intermitting a conduction state of an inductive speaker 2 by a PWM audio signal A for inductive speakers. A control circuit 5 includes a smoothing circuit 10 which smooths a surge voltage caused by intermittence of the switching means 9. Capacitive speaker driving means 8 is a class D amplifier and drives a capacitive speaker 3 using a secondary voltage C' smoothed by the smoothing circuit 10. A surge energy generated due to the intermittence of the switching means 9 is not discarded and is used to drive the capacitive speaker 3, thereby allowing suppression of the power consumption. This also allows avoidance of increases in size and cost of components required when the surge energy is discarded. In addition, a driving voltage of the capacitive speaker 3 is increased because the surge voltage is added to a power-supply voltage.

Description

  The present invention includes an inductive speaker (for example, an electromagnetic vehicle horn) that generates a sound wave by a change in generated magnetic force and a capacitive speaker (for example, a piezoelectric speaker) that generates a sound wave by a change in accumulated charge. The present invention relates to an acoustic device used, and more particularly to a technique suitable for use in a vehicle presence notification device that notifies the presence of a vehicle to the surroundings by a notification sound.

(Background technology)
Background art will be described using a vehicle presence notification device.
There has been proposed a vehicle presence notification device that notifies the presence of a quiet vehicle (such as an electric vehicle) to the surroundings by a notification sound (pseudo engine sound or the like) (for example, see Patent Document 1). The vehicle presence notification device disclosed in Patent Document 1 generates a notification sound from a dynamic speaker (a speaker that directly emits an audible sound).
The audible sound directly generated by the dynamic speaker has a property of spreading to the surroundings. For this reason, if the notification sound is generated far away in the traveling direction of the vehicle, the notification sound with a large sound pressure reaches the direction different from the traveling direction of the vehicle (including the passenger compartment). It becomes a factor of noise.

To solve this problem, a technique using a parametric speaker instead of a dynamic speaker has been proposed (for example, Patent Document 2). A parametric loudspeaker is a modulation component included in the ultrasonic wave (a sound wave that cannot be heard by the ear) by ultrasonically modulating the notification sound (audible sound) (irradiating the original sound with the ultrasonic wave) and irradiating it from the ultrasonic speaker into the air. Is self-demodulated in the air in the middle of propagation, thereby generating a notification sound at a location away from the ultrasonic speaker.
Since this parametric speaker is a technology that uses ultrasonic waves with high directivity (straightness), it is possible to generate a notification sound only in front of the vehicle, and avoid the problem that the notification sound causes noise. it can.

However, since the technology for generating the notification sound using the parametric speaker generates the notification sound only in front of the vehicle, no notification sound is generated except in the front of the vehicle, and the presence of the vehicle in other than the front of the vehicle. Cannot be notified with a notification sound.
Therefore, as means for avoiding the above-described problem, a vehicle presence notification device has been proposed (not a well-known technique) that generates notification sound from both the dynamic speaker and the parametric speaker and complements the disadvantages of both.

(Problem 1)
Problem 1 will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the related form of "the form for inventing" mentioned later and the "Example." Moreover, the technique shown by the following problems is a technique disclosed in order to explain the difference with this invention, and is not a well-known technique.

As the dynamic speaker, an inductive speaker 2 that can easily drive a vibration system having a large mass is generally used.
In addition, as an ultrasonic speaker that generates ultrasonic waves in a parametric speaker, a capacitive speaker 3 in which a vibration system can be easily provided is generally used.

FIG. 12 shows an example of a control circuit 5 that controls energization of the inductive speaker 2 and the capacitive speaker 3.
(A) An inductive speaker PWM audio signal A (audible sound PWM signal) serving as a drive signal for the inductive speaker 2 and a capacitive speaker PWM audio signal E (for ultrasonic waves) serving as a drive signal for the capacitive speaker 3 Two-channel PWM sound source 6 for generating a PWM signal),
(B) Inductive speaker driving means 7 for generating an inductive speaker driving signal C by the inductive speaker PWM audio signal A;
(C) capacitive speaker drive means 8 for generating a capacitive speaker drive signal F by the capacitive speaker PWM audio signal E;
Is provided.

FIG. 13 shows the waveform of each part accompanying the operation of the control circuit 5, from the top to the bottom of FIG.
Inductive speaker PWM audio signal A, which is a drive signal for the inductive speaker 2
An inductive speaker drive signal C applied to the inductive speaker 2;
-The output waveform D of the inductive speaker 2,
A capacitive speaker PWM audio signal E that is a drive signal for the capacitive speaker 3;
A capacitive speaker drive signal F applied to the capacitive speaker 3;
-Output waveform G of the capacitive speaker 3,
-Waveform signal H of parametric playback sound, in which the ultrasonic waveform is self-demodulated in air,
Is shown.

In FIG. 12, the battery 4 of 12V is used as the main power source. However, as shown in FIG. 13, the maximum amplitude of the capacitive speaker drive signal F given to the capacitive speaker 3 is ± 30V. explain.
The capacitive speaker driving means 8 mounted in the control circuit 5 of FIG. 12 is the capacitive speaker 3 by the capacitive speaker PWM audio signal E, as in “Mode for Carrying Out the Invention” and “Example” described later. This is a push-pull class D amplifier that switches between positive and negative voltages. A coil (not shown) is provided at the output portion of the capacitive speaker driving means 8 (class D amplifier), and operates as a series resonance circuit including the coil and the capacitive speaker 3, and the resonance frequency is selected by selecting the inductance of the coil. Is adjusted to the carrier frequency (for example, 40 kHz) of the capacitive speaker 3 to obtain a voltage width (± 30 V) that is five times the supply voltage (12 V). Note that 5 times is a specific example for explanation and can be changed.

Here, the inductive speaker driving means 7 of FIG. 12 is the switching means 9 for switching the inductive state of the inductive speaker 2 by the inductive speaker PWM audio signal A, as in the present invention.
Thus, by using the switching means 9 as the inductive speaker driving means 7,
(I) An alarm sound can be generated from the vehicle horn by intermittently controlling the switching means 9 with a PWM signal in a short time.
(Ii) An alarm sound (a horn sound) can be generated from the vehicle horn by continuously turning on the switching means 9.
That is, both a notification sound and an alarm sound can be generated from the vehicle horn.
Further, since the switching means 9 has a simple circuit configuration, the control circuit 5 can be simplified and the cost can be reduced.

However, when the inductive speaker 2 is intermittently connected by the switching means 9, a peak surge occurs in the inductive speaker drive signal C.
In particular, when an electromagnetic vehicle horn is used as an example of the inductive speaker 2, the coil of the vehicle horn has a large inductance, and thus a large surge energy is generated in the inductive speaker drive signal C.

Since this surge is generated by several hundred volts, it affects the surrounding vehicle electronic equipment as radio noise.
Therefore, it is required to suppress the surge to several tens of volts in order not to generate radio noise from the vehicle horn.
As a means for removing the surge, it is conceivable to provide a snubber circuit 100 as shown in FIG.
However, the snubber circuit 100 throws away the generated surge as heat. As a result, the power of the battery 4 cannot be used effectively, and the power consumption of the battery 4 increases.

Furthermore, since the snubber circuit 100 is required to have a performance sufficient to dissipate the surge energy as heat, large and expensive parts are required, and the installation of the snubber circuit 100 increases the cost.
In particular, when an electromagnetic vehicle horn is used as an example of the inductive speaker 2, a large surge energy is thrown away as heat in the snubber circuit 100. Therefore, the snubber circuit 100 requires particularly large and expensive components. This causes deterioration in mountability of the control circuit 5 and cost increase.

In the above, the problem in the case of using the switching means 9 for the inductive speaker driving means 7 has been described. However, even if another means different from the switching means 9 is used for the inductive speaker driving means 7, the same problem as described above occurs.
Specific examples thereof will be described in Problems 2 and 3.

(Problem 2)
The inductive speaker driving means 7 in FIG. 14 is a class B amplifier 102 that drives the inductive speaker 2 by converting the inductive speaker PWM audio signal A into a voltage change by the filter 101.
When the inductive speaker 2 is driven by the class B amplifier 102, the above-described surge does not occur, but electric energy corresponding to the surge energy is consumed by the power amplifying element (transistor or the like) constituting the class B amplifier 102. That is, the power amplification element generates heat. For this reason, it is necessary to throw away the generated heat using the heat sink 103.

As described above, even when the class B amplifier 102 is used as the inductive speaker driving means 7, since the heat generated by the power amplifying element is discarded using the heat sink 103, a part of the electric energy is wasted as heat.
Further, the use of the heat sink 103 increases the size of the control circuit 5 and increases the cost.

(Problem 3)
The inductive speaker driving means 7 in FIG. 15 is a push-pull class D amplifier 104 that switches and applies a positive / negative voltage to the inductive speaker 2 by the inductive speaker PWM audio signal A. Since the class D amplifier 104 is excellent in energy efficiency, the heat sink 103 (see Problem 2) may not be used.
However, in order to drive the inductive speaker 2 by the class D amplifier 104, it is necessary to provide a filter 105 composed of a coil and a capacitor at the output part of the class D amplifier 104.
In particular, when an electromagnetic vehicle horn is used as an example of the inductive speaker 2, the inductance of the coil mounted on the vehicle horn is large, so that a large and expensive coil and capacitor corresponding to a large current are required. As the circuit 5 becomes larger, the cost increases.

JP 2005-289175 A JP 2011-050184 A

  The present invention has been made in view of the above problems, and its purpose is to drive a capacitive speaker without throwing away the surge energy generated when the energization state of the inductive speaker is interrupted by the switching means. It is an object of the present invention to provide an audio device that can suppress power consumption by avoiding the increase in size and cost of parts required when throwing away surge energy.

[Means of Claim 1]
The inductive speaker driving means for driving the inductive speaker is a switching means, and the conductive state of the inductive speaker is interrupted by a PWM signal (inductive speaker PWM audio signal). A surge occurs in the energizing circuit of the inductive speaker by the switching means intermittently switching the energizing state of the inductive speaker. The capacitive speaker driving means for driving the capacitive speaker drives the capacitive speaker using a DC secondary voltage obtained by smoothing a surge voltage generated by the switching means being intermittent.

(Effect 1 of the invention)
In this way, the surge energy generated when the energization state of the inductive speaker is interrupted by the switching means is used for driving the capacitive speaker without throwing away the surge energy. As a result, power consumption used for driving the capacitive speaker can be suppressed, and as a result, power consumption of the audio device can be suppressed.

(Effect 2 of the invention)
Moreover, since it consumes by driving a capacitive speaker, without throwing away surge energy, it becomes possible to avoid the increase in size and cost of components required when throwing away surge energy.

(Effect 3 of the invention)
Furthermore, since the secondary voltage is a voltage obtained by adding a surge voltage to the power supply voltage, the driving voltage of the capacitive speaker is increased. As a result, the sound pressure of the capacitive speaker can be increased. Alternatively, the number of capacitive speakers used can be reduced.

[Means of claim 2]
The switching means of claim 2 is a low-side type that intermittently connects between an inductive speaker connected to a positive potential of a main power source (for example, a battery) and a ground potential {see FIG. 2 (a)}. Is generated on the positive potential side of the amplifier circuit in the capacitive speaker driving means (see waveform signal C in FIG. 3).

[Means of claim 3]
The switching means according to claim 3 is a high-side type in which the positive potential of the main power source (for example, a battery or the like) and the inductive speaker are intermittently connected (see FIG. 4), and the surge voltage due to the intermittent switching means has a capacity. This occurs on the negative potential side of the amplifier circuit in the characteristic speaker driving means (see waveform signal C in FIG. 5).

[Means of claim 4]
According to a fourth aspect of the present invention, there is provided an acoustic device that generates a capacitive speaker PWM audio signal (capacitive speaker output signal) in response to a change in secondary voltage caused by a change in inductive speaker PWM audio signal (inductive speaker drive signal). Secondary voltage increase / decrease correction means for directly or indirectly correcting the drive signal) is used.
As a result, it is possible to avoid a problem that fluctuations occur in the reproduced sound from the capacitive speaker as the secondary voltage fluctuates (fluctuates).

[Means of claim 5]
The capacitive speaker according to claim 5 is a piezoelectric speaker using a piezoelectric element that is displaced by a change in accumulated charge, and this piezoelectric speaker is used for an ultrasonic speaker that generates ultrasonic waves in a parametric speaker.
Thereby, it can utilize with a parametric speaker, without throwing away surge energy, and can suppress the power consumption of a parametric speaker.

[Means of claim 6]
The inductive speaker according to claim 6 is a dynamic speaker using a coil whose generated magnetic force changes according to a change in applied voltage, and this dynamic speaker generates an alarm sound (horn sound) when a horn switch is operated. This is an electromagnetic vehicle horn.
Since the vehicle horn is used as the inductive speaker, the cost can be reduced and the mounting property on the vehicle can be improved.

[Means of Claim 7]
The acoustic device according to claim 7 is used for a vehicle presence notification device that generates a notification sound outside the vehicle to notify the presence of the vehicle.

It is a schematic block diagram (basic configuration diagram of the invention) of an electric circuit of an acoustic device using switching means as inductive speaker driving means. (A) Schematic block diagram of low-side type booster circuit, (b) Schematic block diagram of booster circuit used for comparison (Embodiment 1). 5 is a time chart for explaining operations using waveform signals (Embodiment 1). FIG. 6 is a schematic block diagram of a high-side type booster circuit (second embodiment). 10 is a time chart for explaining an operation using a waveform signal (second embodiment). 1 is a schematic diagram of a vehicle presence notification device (Example 1). FIG. 3 is a vehicle mounting diagram of an ultrasonic speaker and a vehicle horn (Example 1). (A) It is sectional drawing which shows the structure of the horn for vehicles, (b) It is a perspective view of the horn for vehicles equipped with the ultrasonic speaker (Example 1). (Example 2) which is the schematic of a vehicle presence alerting | reporting apparatus. (Example 3) which is the schematic of a vehicle presence alerting | reporting apparatus. (Example 4) which is the schematic of a vehicle presence alerting | reporting apparatus. It is a schematic block diagram of the electric circuit of the acoustic apparatus which used the switching means for the inductive speaker drive means (reference example 1). It is a time chart for operation explanation using a waveform signal (reference example 1). It is a schematic block diagram of the electric circuit of the audio equipment which uses class B amplifier for inductive speaker drive means (reference example 2). It is a schematic block diagram of the electric circuit of the audio equipment which used push pull class D amplifier for the inductive speaker drive means (reference example 3).

An embodiment of the present invention will be described with reference to FIGS.
The acoustic device 1 of the present invention includes:
(A) an inductive speaker 2 that generates sound waves by a change in generated magnetic force;
(B) a capacitive speaker 3 that generates sound waves by a change in accumulated charge;
(C) a control circuit 5 that controls the operation of the inductive speaker 2 and the capacitive speaker 3 using the power supplied from the main power supply 4;
It comprises.

The control circuit 5
(D) a two-channel PWM sound source 6 for generating an inductive speaker PWM audio signal A as a drive signal for the inductive speaker 2 and a capacitive speaker PWM audio signal E as a drive signal for the capacitive speaker 3;
(E) Inductive speaker driving means 7 for driving the inductive speaker 2 by the inductive speaker PWM audio signal A;
(F) capacitive speaker driving means 8 for driving the capacitive speaker 3 by the PWM audio signal E for capacitive speaker;
It comprises.

The inductive speaker driving means 7 is switching means 9 for switching the inductive state of the inductive speaker 2 by the inductive speaker PWM audio signal A obtained by PWM modulating the audible sound signal.
Further, the control circuit 5 includes a smoothing circuit 10 that smoothes a surge voltage generated by the intermittent switching means 9.
Furthermore, the capacitive speaker driving means 8 uses the voltage smoothed by the smoothing circuit 10 (a DC secondary voltage C ′ obtained by smoothing the surge voltage generated by the intermittent switching means 9) to cause the capacitive speaker 3 to operate. To drive.

In this way, the surge energy generated when the energization state of the inductive speaker 2 is intermittently switched by the switching means 9 is used for driving the capacitive speaker 3 without being discarded, and thus used for driving the capacitive speaker 3. Power consumption can be reduced.
In addition, since it consumes by driving the capacitive speaker 3 without throwing away the surge energy, it becomes possible to avoid the increase in size and cost of parts required when throwing away the surge energy, and the control circuit. 5 can be reduced in size and cost.

Furthermore, since the secondary voltage C ′ (the voltage smoothed by the smoothing circuit 10) is a voltage obtained by adding a surge voltage to the power supply voltage, the driving voltage of the capacitive speaker 3 is increased. As a result, the sound pressure of the capacitive speaker 3 can be increased. Alternatively, when a plurality of capacitive speakers 3 are used, the number of capacitive speakers 3 to be used can be reduced.
A specific example in which the drive voltage of the capacitive speaker 3 is increased by the surge voltage will be described using “Embodiments 1 and 2”. The first embodiment shows an example of boosting by the low side, and the second embodiment shows an example of boosting by the high side.

[Embodiment 1]
The first embodiment will be described with reference to FIGS.
The switching means 9 of the first embodiment is a low-side type that intermittently connects between the inductive speaker 2 connected to the positive potential (12 V as an example) of the battery 4 (an example of the main power source) and the ground potential. 9 is generated on the positive potential side of the amplifier circuit in the capacitive speaker driving means 8.

Here, FIG. 3 shows a specific example of the waveform of each part accompanying the operation of the control circuit 5, from the top to the bottom of FIG.
Inductive speaker PWM audio signal A, which is a drive signal for the inductive speaker 2
An inductive speaker drive signal C applied to the inductive speaker 2;
-The output waveform D of the inductive speaker 2,
・ Secondary voltage C ′ (battery voltage + B plus smoothing voltage α for positive surge),
A capacitive speaker PWM audio signal E that is a drive signal for the capacitive speaker 3;
A capacitive speaker driving signal F (ultrasonic driving signal) given to the capacitive speaker 3;
-Output waveform G of the capacitive speaker 3,
-Waveform signal H of parametric playback sound, in which the ultrasonic waveform is self-demodulated in air,
Is shown.

By switching the energizing state of the inductive speaker 2 by the switching means 9 by the inductive speaker PWM audio signal A, the surge voltage generated on the positive potential side is added to the battery voltage + B without being discarded. As a result, the secondary voltage C ′ smoothed by the smoothing circuit 10 is boosted, and the driving voltage of the capacitive speaker 3 is increased.
Thereby, the sound pressure of the capacitive speaker 3 can be increased. Alternatively, the number of capacitive speakers 3 to be used can be reduced.

(Comparison explanation)
Unlike the present invention, it is conceivable to use a booster circuit as means for increasing the drive voltage of the capacitive speaker 3.
A specific example of a general booster circuit is shown in FIG. In FIG. 2B, the choke coil (inductance) X1 arranged in the voltage supply circuit is intermittently connected by the switching means 9, and the symbol X2 in the figure indicates the intermittent signal (step-up PWM). It is a switching signal generator that provides a signal A ′).

When the drive voltage of the capacitive speaker 3 is increased using the existing booster circuit shown in FIG. 2B, it is necessary to separately install a dedicated booster circuit, which causes an increase in cost.
On the other hand, since the present invention increases the drive voltage of the capacitive speaker 3 by using the surge voltage without discarding it, it is not necessary to separately install a dedicated booster circuit.
That is, the present invention can increase the driving voltage of the capacitive speaker 3 without separately mounting a dedicated booster circuit.

In addition, although secondary voltage C 'is about 18V, it demonstrates that the maximum amplitude of the capacitive speaker drive signal F given to the capacitive speaker 3 is +/- 45V.
The capacitive speaker driving means 8 in this embodiment is a push-pull class D amplifier that switches and applies a positive / negative voltage to the capacitive speaker 3 by the PWM audio signal E for capacitive speaker. A coil (not shown) is provided at the output portion of the capacitive speaker driving means 8 (class D amplifier), and operates as a series resonance circuit including the coil and the capacitive speaker 3, and the resonance frequency is selected by selecting the inductance of the coil. Is adjusted to a carrier frequency (for example, 40 kHz) of the capacitive speaker 3 to obtain a voltage width (± 45 V) that is five times the secondary voltage C ′ (18 V). In addition, 5 times shows a specific example and can be changed suitably.

[Embodiment 2]
The second embodiment will be described with reference to FIGS. 4 and 5.
The switching means 9 of the second embodiment is a high-side type in which the positive potential (12 V as an example) of the battery 4 (an example of the main power supply) and the inductive speaker 2 are intermittently connected. A voltage is generated on the negative potential side of the amplifier circuit in the capacitive speaker driving means 8.

Here, FIG. 5 shows a specific example of the waveform of each part accompanying the operation of the control circuit 5, from the top to the bottom of FIG.
Inductive speaker PWM audio signal A, which is a drive signal for the inductive speaker 2
An inductive speaker drive signal C applied to the inductive speaker 2;
-The output waveform D of the inductive speaker 2,
・ Secondary voltage C ′ (battery voltage + B and the difference voltage between the negative side surge and the smoothing voltage −α),
A capacitive speaker PWM audio signal E that is a drive signal for the capacitive speaker 3;
A capacitive speaker drive signal F applied to the capacitive speaker 3;
-Output waveform G of the capacitive speaker 3,
-Waveform signal H of parametric playback sound, in which the ultrasonic waveform is self-demodulated in air,
Is shown.

By switching the inductive state of the inductive speaker 2 by the switching means 9 by the inductive speaker PWM audio signal A, the surge voltage generated on the negative potential side is not discarded and is added to the negative side of the battery voltage (12V). The As a result, the voltage width of the secondary voltage C ′ smoothed by the smoothing circuit 10 is increased, and the driving voltage of the capacitive speaker 3 is increased.
Thereby, the sound pressure of the capacitive speaker 3 can be increased. Alternatively, the number of capacitive speakers 3 to be used can be reduced.

Hereinafter, specific examples (examples) in which the present invention is applied to the vehicle presence notification device 1 will be described with reference to the drawings. The following examples show specific examples, and it goes without saying that the present invention is not limited to the examples.
In the following examples, the same reference numerals as those in the “DETAILED DESCRIPTION OF THE INVENTION” denote related items.

[Example 1]
Embodiment 1 will be described with reference to FIGS.
The vehicle presence notification device 1 notifies the presence of a vehicle by a notification sound (audible sound: pseudo engine sound or the like), for example, a vehicle (electric vehicle, fuel cell vehicle, etc.) not equipped with an engine (internal combustion engine), traveling Vehicles that may stop the engine during and when the vehicle is stopped (hybrid vehicles, etc.), vehicles that may stop the engine while the vehicle is stopped (idle stop vehicles, etc.) It will be installed in a variety of vehicles.

This vehicle presence notification device 1
A vehicle horn 2 (an example of an inductive speaker) used as a dynamic speaker that emits an audible notification sound directly outside the vehicle;
A parametric speaker 11 that emits an ultrasonic wave that is obtained by ultrasonically modulating a waveform signal that forms a notification sound;
A control circuit 5 that controls the operation of the vehicle horn 2 and the parametric speaker 11 is provided.

(Description of vehicle horn 2)
The vehicle horn 2 is an electromagnetic sounding device that generates an alarm sound when a horn switch 12 (for example, a steering horn button) is operated by an occupant, and is provided at the front of the vehicle as shown in FIG. Fixed between the front grill 13 and the heat exchanger 14 (radiator, heat exchanger for air conditioning, etc.) disposed therein.

A specific example of the vehicle horn 2 will be described with reference to FIG.
The vehicle horn 2 is
A coil 21 that generates magnetic force when energized;
A fixed iron core 22 (magnetic attraction core) that generates a magnetic attraction force by the magnetic force of the coil 21;
A movable iron core 24 (movable core) supported at the center of the diaphragm 23 (diaphragm) and movably supported toward the fixed iron core 22;
In conjunction with the movement of the movable iron core 24, the movable iron core 24 moves toward the fixed iron core 22 to move away from the fixed contact 25 to interrupt the energization of the coil 21,
Is provided.

And, by applying a self-excited voltage (voltage of 8 V or more) equal to or higher than a threshold value to a direct current to the energization terminal (terminal connected to both ends of the coil 21) of the vehicle horn 2,
(I) A suction operation in which the movable iron core 24 is magnetically attracted to the fixed iron core 22 by energization of the coil 21, the movable contact 26 is separated from the fixed contact 25, and energization of the coil 21 is stopped;
(Ii) Restoration in which the diaphragm 23 applies an action of a return spring to the movable iron core 24 by stopping the energization, the movable iron core 24 returns to the initial position, the fixed contact 25 and the movable contact 26 come into contact, and the energization of the coil 21 is resumed. Operation and
Repeat continuously.

That is, the fixed contact 25 and the movable contact 26 constitute a current interrupter 27 that interrupts the energization circuit of the coil 21.
As described above, intermittent energization of the coil 21 (intermittent generation of magnetic attractive force of the fixed iron core 22) causes the vibration plate 23 to vibrate together with the movable iron core 24, and the vehicle horn 2 generates an alarm sound.

On the other hand, the vehicle horn 2 can be used as a dynamic speaker by applying to the coil 21 a drive signal having a separate excitation voltage (for example, a voltage of less than 8V) lower than the self-excitation voltage.
Or even if it is self-excited voltage, the horn 2 for vehicles is used as a dynamic speaker by carrying out the quick intermittent control (PWM control etc.) of the energization state of the coil 21 within the short time which does not generate | occur | produce intermittent in the current interrupter 27. be able to.
In this embodiment, the latter (the coil 21 is quickly intermittently controlled using a self-excited voltage) is employed, and the vehicle horn 2 is used as a dynamic speaker.

The vehicle horn 2 shown in this embodiment includes a spiral horn 28 (a spiral trumpet member: a spiral acoustic tube) that enhances an alarm sound due to vibration of the diaphragm 23 and emits it outside the vehicle. The notification sound generated from the horn 2 is mounted on the vehicle so that the opening portion of the spiral horn 28 faces downward (road surface) so that the notification sound reaches the periphery of the vehicle substantially evenly.
The vehicle horn 2 is not limited to the one provided with the spiral horn 28 and may be a disk type horn that does not use the spiral horn 28.

(Description of parametric speaker 11)
The ultrasonic speaker 31 used for the parametric speaker 11 generates air vibration having a frequency (20 kHz or more) higher than the human audible band, and is mounted on the vehicle so as to emit ultrasonic waves toward the front of the vehicle. ing.
Specifically, the ultrasonic speaker 31 of this embodiment is provided on the front surface of the vehicle horn 2 (the surface facing the front of the vehicle when the vehicle is mounted: for example, the spiral horn 28), and the front grill 13 and the heat exchanger 14 are provided. By attaching the vehicle horn 2 between the two, the ultrasonic speaker 31 is mounted on the vehicle in a state where the ultrasonic radiation direction is directed forward of the vehicle.

As shown in FIG. 7, the ultrasonic speaker 31 of this embodiment is equipped with a plurality of piezoelectric speakers 3 (an example of capacitive speakers) that generate ultrasonic waves, and the plurality of piezoelectric speakers 3 are housings. It is mounted on the vehicle in a state of being housed inside 32.
The plurality of piezoelectric speakers 3 are mounted on a support plate 33 that is fixedly disposed inside the housing 32 and are collectively disposed as a speaker array. Each piezoelectric speaker 3 includes a piezoelectric element (piezoelectric element) that expands and contracts according to a change in applied voltage (accumulated charge), and a diaphragm that is driven by the expansion and contraction of the piezoelectric element to generate a dense wave in the air. It is configured by using.

The housing 32 may be provided integrally with a member constituting the vehicle horn 2 or may be provided separately and attached to the vehicle horn 2.
The ultrasonic radiation opening of the housing 32 is provided with waterproof means for preventing rainwater from entering the mounting portions of the piezoelectric speakers 3.
As an example of this waterproofing means, in this embodiment, an ultrasonically transparent waterproof sheet 34 covering the ultrasonic radiation opening and a louver 35 disposed on the front surface of the waterproof sheet 34 are provided {FIG. a) shows a view in which the waterproof sheet 34 and the louver 35 are omitted}.

(Description of control circuit 5)
The control circuit 5 is configured by using a microcomputer 41 (abbreviation of a microcomputer) as shown in FIG. 7. For example, as shown in FIG. 7, the control circuit 5 is arranged inside the vehicle horn 2 (specifically Specifically, it is arranged (not limited) inside the horn housing.

The control circuit 5 will be specifically described with reference to FIG.
The microcomputer 41 operates by 5V (voltage suitable for the operation of the microcomputer 41) generated by stepping down from the battery voltage.
The microcomputer 41 is provided with a vehicle speed signal (vehicle speed pulse or the like) from an operation signal of the horn switch 12 or an ECU 42 (abbreviation of engine control unit), and a notification sound is generated according to the driving state of the vehicle. A control program is installed that is generated and changes the tone color of the notification sound (for example, the tone color corresponding to the vehicle speed of the pseudo engine sound) according to the vehicle speed or the like.

Specifically, the configuration of the main part of the microcomputer 41 will be described.
The microcomputer 41 includes the function of the two-channel PWM sound source 6 described above, and includes a period measurement unit 51, a timer counter 52, an audio memory 53, an inductive speaker PWM modulation unit 54, and a capacitive speaker PWM modulation unit 55. It is configured with.
The vehicle speed signal (vehicle speed pulse or the like) given from the ECU 42 is periodically measured by the cycle measuring unit 51 to calculate the vehicle speed.

In the sound memory 53, sound data that makes a notification sound corresponding to the vehicle speed (specifically, a pseudo engine sound corresponding to the vehicle speed) is stored in advance. Then, audio data corresponding to the vehicle speed is selected and sequentially output by the timer counter 52. Specifically, the timer counter 52 outputs the audio data in the audio memory 53 to both the inductive speaker PWM modulation unit 54 and the capacitive speaker PWM modulation unit 55 at the same rate as the sampling rate at the time of recording.
That is, a “waveform signal forming a notification sound” corresponding to the vehicle speed is output to the inductive speaker PWM modulation unit 54 and the capacitive speaker PWM modulation unit 55.

The inductive speaker PWM modulation unit 54 generates an inductive speaker PWM audio signal A (a driving signal for the vehicle horn 2) obtained by PWM-modulating the “waveform signal forming the notification sound”.
Here, the PWM modulation frequency (pulse generation frequency) in the PWM modulation unit 54 for the inductive speaker is a frequency of 20 kHz or more, and is provided so that the sound of the frequency used for the PWM modulation is not reproduced from the vehicle horn 2. It has been.

The capacitive speaker PWM modulation unit 55 performs PWM modulation of the “DSB-modulated waveform signal that forms the notification sound” using the PWM modulation technique, and the capacitive speaker PWM audio signal E (of the ultrasonic speaker 31). Drive signal).
Here, a frequency obtained by multiplying the resonance frequency of the piezoelectric speaker 3 by a positive number is used as a PWM modulation frequency (pulse generation frequency) in the PWM modulation unit 55 for the capacitive speaker, and an ultrasonic wave is generated from the piezoelectric speaker 3 by the PWM signal. It is provided to occur.

In addition to the microcomputer 41 described above, the control circuit 5 includes
Inductive speaker driving means 7 for driving the vehicle horn 2 (inductive speaker);
A capacitive speaker driving means 8 for driving each piezoelectric speaker 3 (capacitive speaker) in the ultrasonic speaker 31;
A smoothing circuit 10 for smoothing a surge voltage generated by the intermittent switching means 9;
Is provided.

  The inductive speaker driving means 7, as shown in “Mode for Carrying Out the Invention”, interrupts the energized state of the vehicle horn 2 by the inductive speaker PWM audio signal A obtained by PWM-modulating the audible sound signal. Switching means 9 (semiconductor switching elements such as bipolar transistors and FETs), which may be the low side type shown in “Embodiment 1” or the high side type shown in “Embodiment 2”. Also good.

  The capacitive speaker driving means 8 is a push-pull class D amplifier (switching the positive and negative voltages applied to each piezoelectric speaker 3 by the capacitive speaker PWM audio signal E and applying the positive and negative voltages to each piezoelectric speaker 3 by the capacitive speaker PWM audio signal E. (Amplifier comprising a piezo charge switching unit for turning on and off one pole and a piezo discharge switching unit for turning on and off the other pole of each piezoelectric speaker 3 by a reverse signal obtained by inverting the PWM audio signal E for capacitive speaker) It is.

As described above, the smoothing circuit 10 smoothes the surge voltage generated by the switching means 9 being intermittent, and includes at least a backflow preventing diode 56 and a capacitor 57 that suppresses voltage fluctuation (reference numeral). FIG. 2 and FIG. 4). The secondary voltage C ′ smoothed by the smoothing circuit 10 is applied to the capacitive speaker driving means 8 (class D amplifier).
The capacitive speaker driving means 8 (class D amplifier) performs charge / discharge control of each piezoelectric speaker 3 using the secondary voltage C ′ smoothed by the smoothing circuit 10.

The microcomputer 41 has a function of continuously turning on the switching means 9 while the horn switch 12 is ON, and applying a battery voltage to the vehicle horn 2 to generate an alarm sound from the vehicle horn 2. Is provided.
In addition, the microcomputer 41 has a function of giving priority to “ON of the horn switch 12” over “the condition for generating the notification sound” and always generating an alarm sound from the vehicle horn 2 when the horn switch 12 is turned ON. It has been.

(Operation of the vehicle presence notification device 1)
When the driving state of the vehicle matches the generation condition of the notification sound, the “waveform signal forming the notification sound (pseudo engine sound etc.)” corresponding to the vehicle speed is extracted from the voice memory 53,
(I) The inductive speaker PWM sound signal A obtained by PWM modulating the “waveform signal forming the notification sound” is supplied from the inductive speaker PWM modulation unit 54 to the switching means 9;
(Ii) The capacitive speaker PWM audio signal E obtained by ultrasonically modulating the “waveform signal forming the notification sound” by PWM modulation is supplied from the capacitive speaker PWM modulator 55 to the capacitive speaker driving means 8.

By switching the switching means 9 by the inductive speaker PWM sound signal A, an audible “notification sound” is directly emitted from the vehicle horn 2 to the surroundings of the vehicle.
On the other hand, when the capacitive speaker driving means 8 drives each piezoelectric speaker 3 of the ultrasonic speaker 31 by the PWM audio signal E for capacitive speaker, ultrasonic waves obtained by DSB modulating the notification sound are emitted to the front of the vehicle. . As the ultrasonic wave emitted forward of the vehicle propagates through the air, the ultrasonic wave having a short wavelength is distorted and blunted by the viscosity of the air and the like. As a result, the modulation component contained in the ultrasonic wave in the air that is being propagated is self-demodulated, and as a result, “notification sound” is reproduced in front of the vehicle.

(Effect 1 of Example 1)
The vehicle presence notification device 1 according to this embodiment, when generating a notification sound from the vehicle horn 2, drives a capacitive speaker without throwing away the surge energy generated when the vehicle horn 2 is intermittently switched by the switching means 9. It is used for driving each piezoelectric speaker 3 in the ultrasonic speaker 31 by using it as a power source for the means 8 (class D amplifier). As a result, power consumption used for driving the ultrasonic speaker 31 can be suppressed, and as a result, battery consumption associated with the operation of the vehicle presence notification device 1 can be suppressed.

(Effect 2 of Example 1)
Since the vehicle presence notification device 1 of this embodiment consumes by driving the ultrasonic speaker 31 without throwing away the surge energy, it avoids the increase in size and cost of parts required when throwing away the surge energy. Therefore, the control circuit 5 can be reduced in size and cost, and the mounting property on the vehicle can be improved.

(Effect 3 of Example 1)
Since the secondary voltage C ′ smoothed by the smoothing circuit 10 is a voltage obtained by adding the smoothed surge voltage to the battery voltage, the driving voltage of the ultrasonic speaker 31 is increased.
Thereby, the sound pressure (ultrasonic sound pressure) generated by the ultrasonic speaker 31 can be increased. Alternatively, the number of piezoelectric speakers 3 used for the ultrasonic speaker 31 can be reduced, and the cost of the ultrasonic speaker 31 can be reduced.

  Since the secondary voltage C ′ is boosted by using a surge voltage, the microcomputer 41 has a function of adjusting the secondary voltage C ′ by performing an offset operation on the pulse width of the PWM audio signal A for inductive speakers. It may be provided.

(Effect 4 of Example 1)
In this embodiment, the vehicle horn 2 that generates an alarm sound (horn sound) when the horn switch 12 is pressed is used as an “inductive speaker that generates a notification sound”.
For this reason, it is not necessary to separately mount the “inductive speaker that generates the notification sound” on the vehicle, and it is possible to reduce the cost and secure the vehicle mounting property.

[Example 2]
Embodiment 2 will be described with reference to FIG.
As described above, the secondary voltage C ′ used for the power source of the capacitive speaker driving unit 8 uses a surge voltage generated by the switching unit 9 being intermittently generated by the PWM audio signal A for the inductive speaker. For this reason, the secondary voltage C ′ fluctuates (fluctuates) in accordance with the change of the “waveform signal forming the notification sound (pseudo engine sound etc.)”.
When the secondary voltage C ′ fluctuates (fluctuates), the sound pressure generated by the ultrasonic speaker 31 fluctuates. As a result, the parametric reproduction sound generated by the parametric speaker 11 fluctuates.

This defect will be specifically described.
When the booster circuit shown in FIG. 2B of “Embodiment 2” is used, the boosted secondary voltage C ′ is fed back to the switching signal generator X2, and the switching means 9 is intermittently connected. The boost voltage can be controlled to be constant by changing the duty ratio.
However, in the vehicle presence notification device 1, the PWM signal that interrupts the switching means 9 is the inductive speaker PWM sound signal A for generating the notification sound from the vehicle horn 2, and therefore the secondary voltage C ′. In order to make the frequency constant, the duty ratio of the inductive speaker PWM audio signal A cannot be changed by feedback control.

With respect to the above-described problems, the second embodiment and the vehicle presence notification device 1 of the third and fourth embodiments to be described later have a problem that the parametric reproduction sound generated by the parametric speaker 11 fluctuates due to the fluctuation of the secondary voltage C ′. Is to avoid.
Specifically, the control circuit 5 directly or indirectly corrects the capacitive speaker PWM audio signal E in accordance with the change in the secondary voltage C ′ caused by the change of the inductive speaker PWM audio signal A. Secondary voltage increase / decrease correction means 61 is used.

The secondary voltage increase / decrease correction means 61 of the second embodiment will be described.
The secondary voltage increase / decrease correction means 61 according to the second embodiment generates a “waveform signal forming a notification sound” output from the audio memory 53 to the capacitive speaker PWM modulation unit 55 in real time in accordance with a change in the secondary voltage C ′. Feedback correction is performed.

Specifically, the secondary voltage increase / decrease correction means 61 of the second embodiment monitors the secondary voltage C ′ smoothed by the smoothing circuit 10 with the microcomputer 41,
(I) When the monitored secondary voltage C ′ rises, the sound pressure component (voltage) of the “waveform signal forming the notification sound” applied from the audio memory 53 to the capacitive speaker PWM modulator 55 is reduced. Correct,
(Ii) On the contrary, when the monitored secondary voltage C ′ decreases, the sound pressure component (voltage) of the “waveform signal forming the notification sound” given from the audio memory 53 to the capacitive speaker PWM modulator 55 )
This cancels the fluctuation of the parametric reproduction sound caused by the fluctuation of the secondary voltage C ′.

In order to perform this correction, the microcomputer 41 of this embodiment 2
(A) an AD converter 62 (abbreviation of analog-digital converter) for reading the secondary voltage C ′ smoothed by the smoothing circuit 10 by the microcomputer 41;
(B) A correction value for canceling the fluctuation of the secondary voltage C ′ read by the AD converter 62 is calculated, and this correction value is added to the sound pressure component of the “waveform signal forming the notification sound” output from the sound memory 53. Part 63;
Is provided.

  In the second embodiment, the secondary voltage C ′ is monitored and the “waveform signal forming the notification sound” applied to the capacitive speaker PWM modulator 55 is corrected in real time. The output signal of the speaker driving means 8 (drive signal given to the ultrasonic speaker 31) may be monitored to correct the “waveform signal forming the notification sound” given to the capacitive speaker PWM modulator 55 in real time. .

[Example 3]
Embodiment 3 will be described with reference to FIG.
The secondary voltage increase / decrease correction means 61 of the second embodiment needs to calculate the correction value in real time according to the fluctuation of the secondary voltage C ′. For this reason, the microcomputer 41 is required to have a high processing capacity.
On the other hand, the secondary voltage increase / decrease correction means 61 of the third embodiment does not calculate the correction value in real time according to the fluctuation of the secondary voltage C ′, but instead of “the waveform signal forming the notification sound” in the voice memory 53. "Is overwritten on the" waveform signal forming the corrected notification sound "in anticipation of the increase or decrease of the secondary voltage C ', and real-time correction is abolished and an inexpensive microcomputer 41 with low processing capability can be adopted. It is a thing.

An example of the procedure for overwriting the “waveform signal forming the corrected notification sound” in the audio memory 53 will be described with reference to FIG.
When an instruction to start correction is given to the microcomputer 41 by an arbitrarily operable mixing switch 64, the control circuit 5 sequentially generates a notification sound (pseudo engine sound or the like) corresponding to the vehicle speed stored in the voice memory 53. And it reproduces from the ultrasonic speaker 31.

At this time, as in the second embodiment, the secondary voltage C ′ smoothed by the smoothing circuit 10 using the AD converter 62 is monitored.
Then, the “waveform signal forming the notification sound (pre-correction signal)” and “increase / decrease change in the monitored secondary voltage C ′” given from the audio memory 53 to the capacitive speaker PWM modulator 55 using the mixing unit 63. Compare
(I) When the monitored secondary voltage C ′ increases, the sound pressure component (voltage) of the “waveform signal forming the notification sound” in the sound memory 53 is corrected to be small;
(Ii) Conversely, when the monitored secondary voltage C ′ decreases, the sound pressure component (voltage) of the “waveform signal forming the notification sound” in the sound memory 53 is greatly corrected,
A “waveform signal forming a corrected notification sound” is created that cancels the fluctuation of the parametric reproduction sound caused by the fluctuation of the secondary voltage C ′.
Then, the “waveform signal forming the corrected notification sound” corresponding to the vehicle speed obtained by this work is overwritten and saved in the voice memory 53.

  As a result, during operation of the vehicle presence notification device 1, a “waveform signal that forms a corrected notification sound” corresponding to the vehicle speed is provided from the voice memory 53 to the capacitive speaker PWM modulation unit 55. For this reason, the microcomputer 41 does not need to calculate a correction value in real time according to the fluctuation of the secondary voltage C ′, and can employ an inexpensive microcomputer 41 having a low processing capability.

  In the third embodiment, the example in which the secondary voltage C ′ is used when the “waveform signal forming the corrected notification sound” is overwritten has been described. However, the output signal (super signal) of the capacitive speaker driving means 8 is shown. The “waveform signal forming the corrected notification sound” may be calculated using the driving signal of the sound wave speaker 31 and overwritten.

[Example 4]
A fourth embodiment will be described with reference to FIG.
In the third embodiment, the AD converter 62 and the mixing unit 63 are provided in the microcomputer 41, and the “waveform signal forming the notification sound” is changed to the “waveform signal forming the corrected notification sound” based on the fluctuation of the secondary voltage C ′. An example of overwriting is shown. For this reason, the use of the AD converter 62 and the mixing switch 64 increases the cost.
On the other hand, the secondary voltage increase / decrease correction means 61 of the fourth embodiment stores a “waveform signal forming a corrected notification sound” in anticipation of increase / decrease in the secondary voltage C ′ from the beginning in the audio memory 53. Yes, the AD converter 62 and the mixing switch 64 are unnecessary.

A procedure for obtaining the “waveform signal forming the corrected notification sound” to be stored in the voice memory 53 will be described with reference to FIG.
First, a notification sound (pseudo engine sound or the like) corresponding to the vehicle speed is sequentially generated from the vehicle horn 2 and the ultrasonic speaker 31.
At this time, the parametric reproduced sound from the ultrasonic speaker 31 is converted into an electric signal by the microphone 65 and is taken into the personal computer 66 (abbreviation of personal computer).

In the personal computer 66, the “waveform signal forming the notification sound (pre-correction signal)” is compared with the “waveform signal of the parametric reproduction sound” captured by the microphone 65;
(I) When the sound pressure of the parametric reproduction sound increases due to the increase of the secondary voltage C ′, the sound pressure component (voltage) of the “waveform signal forming the notification sound” in the sound memory 53 is corrected to be small;
(Ii) On the contrary, when the sound pressure of the parametric reproduction sound decreases due to the decrease of the secondary voltage C ′, the sound pressure component (voltage) of the “waveform signal forming the notification sound” in the sound memory 53 is greatly corrected. ,
A “waveform signal forming a corrected notification sound” that cancels the variation of the parametric reproduction sound caused by the variation of the secondary voltage C ′ is calculated.

The “waveform signal forming the corrected notification sound” thus obtained is set as master data.
Then, the master data (the waveform signal forming the corrected notification sound) is written into the audio memory 53 of each microcomputer 41 using the programmer 67.

As a result, during operation of the vehicle presence notification device 1, a “waveform signal that forms a corrected notification sound” corresponding to the vehicle speed is provided from the voice memory 53 to the capacitive speaker PWM modulation unit 55. For this reason, as in the third embodiment, the microcomputer 41 does not need to calculate a correction value in real time according to the fluctuation of the secondary voltage C ′, and can employ an inexpensive microcomputer 41 having a low processing capability.
Further, unlike the second and third embodiments, the AD converter 62 and the mixing switch 64 are not required, and thus the cost of the control circuit 5 can be suppressed.

  In the fourth embodiment, an example in which the “waveform signal forming the corrected notification sound” is obtained based on the parametric reproduction sound captured by the microphone 65 is shown. However, the secondary voltage C smoothed by the smoothing circuit 10 is shown. Alternatively, the output signal of the capacitive speaker driving means 8 (the driving signal of the ultrasonic speaker 31) may be taken into the personal computer 66 to obtain a “waveform signal that forms a corrected notification sound” and be used as master data.

  In the above embodiment, the example in which the present invention is applied to the vehicle presence notification device 1 has been described. However, the present invention may be applied to another acoustic device different from the vehicle presence notification device 1.

  In the above-described embodiment, an example in which the electromagnetic vehicle horn 2 is used as an example of the inductive speaker has been described. However, another dynamic speaker that generates a magnetomotive force in a magnetic pole generated by a magnet and drives a diaphragm ( A cone speaker or the like may be used.

  In the above-described embodiment, an example in which the piezoelectric speaker 3 is used as an example of the capacitive speaker has been described. However, other capacitive speakers that generate sound waves by changes in other accumulated charges, such as a capacitor-type speaker, may be used. Further, an inductive speaker with low power consumption such as a ribbon speaker may be used without being bound by the capacitive speaker.

  In the above embodiment, an example in which ultrasonic waves are generated from the capacitive speaker 3 has been shown. However, the capacitive speaker 3 is not limited to the use of the parametric speaker 11, and high-frequency sound from the capacitive speaker 3 can be obtained. It may be generated. Specifically, the capacitive speaker 3 may be used as a tweeter, and a medium / low sound may be generated from the inductive speaker 2, and a high sound may be generated by the capacitive speaker 3. That is, the present invention may be applied to other uses such as an audio device for vehicles.

1 Vehicle presence notification device (acoustic device)
2 Vehicle horn (inductive speaker: dynamic speaker)
3. Piezoelectric speaker (capacitive speaker)
4 Battery (Main power)
7 Inductive speaker driving means 8 Capacitive speaker driving means 9 Switching means 10 Smoothing circuit 11 Parametric speaker 12 Horn switch 21 Coil 31 for generating magnetic force in inductive speaker 61 Ultrasonic speaker 61 Secondary voltage increase / decrease correction means

Claims (7)

An inductive speaker (2) that generates sound waves by a change in the generated magnetic force;
A capacitive speaker (3) that generates sound waves by changes in accumulated charge;
Inductive speaker driving means (7) for driving the inductive speaker (2);
Capacitive speaker driving means (8) for driving the capacitive speaker (3);
Comprising
The inductive speaker driving means (7) is a switching means (9) for switching the inductive state of the inductive speaker (2) by an inductive speaker PWM audio signal (A) obtained by PWM modulating an audible sound signal. And
The capacitive speaker driving means (8) drives the capacitive speaker (3) using a DC secondary voltage (C ') obtained by smoothing a surge voltage generated by the switching means (9) being intermittent. An acoustic device characterized by that. The acoustic device (1) according to claim 1,
The switching means (9) is a low-side type that intermittently connects between the inductive speaker (2) connected to the positive potential of the main power supply (4) that supplies a DC voltage and the ground potential, The acoustic device according to (9), wherein a surge voltage due to the intermittent operation is generated on a positive potential side of an amplifier circuit in the capacitive speaker driving means (8). The acoustic device (1) according to claim 1,
The switching means (9) is a high-side type that intermittently connects between the positive potential of the main power supply (4) that supplies a DC voltage and the inductive speaker (2), and the switching means (9) is intermittently connected. The acoustic device is characterized in that a surge voltage due to the above occurs on the negative potential side of the amplifier circuit in the capacitive speaker driving means (8). In the acoustic device (1) according to any one of claims 1 to 3,
The capacitive speaker driving means (8) drives the capacitive speaker (3) using a PWM audio signal (E) for capacitive speaker obtained by PWM modulating an audible sound signal,
The acoustic device (1) includes the capacitive speaker PWM audio signal (E) according to the fluctuation of the secondary voltage (C ′) caused by the change of the inductive speaker PWM audio signal (A). ) Is used, or a secondary voltage increase / decrease correction means (61) for directly or indirectly correcting is used. In the acoustic device (1) according to any one of claims 1 to 4,
The capacitive speaker (3) is a piezoelectric speaker using a piezoelectric element that is displaced by a change in accumulated charge,
The piezoelectric speaker is used for an ultrasonic speaker (31) that generates ultrasonic waves in a parametric speaker (11). In the acoustic device (1) according to any one of claims 1 to 5,
The inductive speaker (2) is a dynamic speaker using a coil (21) whose generated magnetic force changes due to a change in applied voltage,
The dynamic speaker is an electromagnetic vehicle horn that generates an alarm sound when a horn switch (12) is operated by an occupant. In the acoustic device (1) according to any one of claims 1 to 6,
This acoustic device (1) is used for a vehicle presence notification device that generates a notification sound outside the vehicle to notify the presence of the vehicle.

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