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DESCRIPTION JP2012192865

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DESCRIPTION JP2012192865
An object of the present invention is to reduce the cost of a vehicle presence notification device
that generates a notification sound using a parametric speaker. SOLUTION: An ultrasonic speaker
2 for generating an ultrasonic wave in a parametric speaker is not provided for generating an
ultrasonic wave, and a piezoelectric speaker 3 for generating an audible sound (a primary
resonance portion exists in an audible band) The modulation frequency at which the notification
sound is ultrasonically modulated is a sound pressure increasing portion by a high-order
resonance portion existing in the ultrasonic band of the reproducible frequency of the
piezoelectric speaker 3 for generating an audible sound. Set to X As a result, ultrasonic waves to
be used for parametric speakers can be generated from the piezoelectric speaker 3 for audible
sound generation that has high versatility and low cost, and the cost of the vehicle presence
notification device using the parametric speakers can be suppressed. [Selected figure] Figure 1
Vehicle presence notification device
[0001]
The present invention relates to a vehicle presence notification device that generates a
notification sound outside a vehicle to notify the presence of a vehicle, and is particularly suitable
for use in quiet vehicles such as electric vehicles, fuel cell vehicles, and hybrid vehicles. About.
[0002]
(Prior Art) There has been proposed a vehicle presence notification device for notifying of the
presence of a vehicle by a notification sound (see, for example, Patent Document 1).
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The vehicle presence notification device of Patent Document 1 generates a notification sound
using a dynamic speaker. On the other hand, it is conceivable to use, as a vehicle presence
notification device, a parametric speaker that has strong directivity and generates a notification
sound at a location away from the vehicle. The parametric speaker ultrasonically modulates
"waveform signal of audible sound (reporting sound)" and emits it from the ultrasonic speaker,
and is included in the ultrasonic wave (sound wave that can not be heard by the ear) emitted
from the ultrasonic speaker The modulation component is self-demodulated in the air on the way
of propagation to generate an audible sound (a notification sound) at a location away from the
vehicle.
[0003]
(Problem) The ultrasonic speaker used for the parametric speaker needs to generate compression
wave of ultrasonic wavelength in the air. Therefore, as shown in FIG. 8A, in the ultrasonic
speaker 2, a plurality of ultrasonic wave generating elements SS (ultrasonic transducers)
provided for generating ultrasonic waves are collectively arranged to form a plurality of
ultrasonic waves. The generating element SS is provided to generate an ultrasonic wave. FIG. 8A
is a reference example shown to aid understanding, and is not a known technique.
[0004]
Here, due to the necessity of generating compression waves of ultrasonic wavelength in air, it is
required that the vibration system (diaphragm + drive element etc.) of the ultrasonic wave
generation element SS be super lightweight and vibrate at high speed. Specifically, as shown in
FIG. 8B, in the ultrasonic wave generation element SS, the primary resonance portion (primary
resonance frequency: first order component) of the vibration system is in the ultrasonic wave
band (about 40 kHz in this example) Provided to be present. As described above, the ultrasonic
wave generating element SS whose vibration system is ultra-light weight is low in versatility, and
the cost is high. For this reason, it becomes a factor of the cost increase of the vehicle presence
notification apparatus using a parametric speaker.
[0005]
JP, 2005-289175, A
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[0006]
The present invention has been made in view of the above problems, and an object thereof is to
suppress the cost of a vehicle presence notification device that generates a notification sound
using a parametric speaker.
[0007]
The ultrasonic speaker of the vehicle presence notifying apparatus according to claim 1 is a
piezoelectric speaker for generating audible sound (provided to generate a sound wave in the
audible band) in which the primary resonance unit is present in the audible band. The
modulation frequency for ultrasonically modulating the notification sound in the parametric
speaker is the sound pressure raising portion in the high-order resonance portion existing in the
ultrasonic band of the reproducible frequency of the piezoelectric speaker for audible sound
generation. It is set (within the rise range of sound pressure).
By providing in this way, an ultrasonic wave used for a parametric speaker can be generated
from the audible sound generating piezoelectric speaker.
On the other hand, a piezoelectric speaker for producing audible sound is versatile and massproduced, so that the cost is low. As a result, the cost of the ultrasonic speaker can be
suppressed, and the cost of the vehicle presence notification device using the parametric speaker
can be suppressed.
[0008]
[Means of Claim 2] The control circuit of Claim 2 generates a "sound wave in the audible range"
from the piezoelectric speaker for generating audible sound. By generating a sound wave in the
audible band from the audible sound generating piezoelectric speaker, it becomes possible to
generate a notification sound outside the range of the directivity of the parametric speaker.
[0009]
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According to the third aspect of the present invention, the control circuit of the third aspect
simultaneously generates “sound waves of plural frequencies” at least in the audible band
from the piezoelectric speaker for generating audible sound, and “sound waves of plural
frequencies” is a chord. The relationship between By providing in this way, even if the
resonance sound is generated in the audible band when the piezoelectric speaker for audible
sound generation generates an ultrasonic wave, "the resonance sound can be made part of a
chord", and the resonance sound can be generated. Can ease the discomfort caused by
[0010]
(A) An explanatory view showing an arrangement example of an audible sound generating
piezoelectric speaker, and (b) a frequency characteristic diagram of the audible sound generating
piezoelectric speaker (Example). It is the schematic of a vehicle presence notification apparatus.
It is a vehicle mounting view of an ultrasonic speaker and the horn for vehicles. (A) A schematic
sectional view for explaining the structure of an ultrasonic speaker and a horn for a vehicle, (b) A
perspective view of the horn for a vehicle provided with the ultrasonic speaker. It is a graph
which shows the frequency characteristic at the time of operating the horn for vehicles by selfexcitation, and operating it by other encouragement. It is explanatory drawing which shows the
arrival range of a notification sound. It is principle explanatory drawing of a parametric speaker.
(A) Explanatory drawing which shows the example of arrangement | positioning of an ultrasonic
wave generation element, (b) It is a frequency characteristic figure of an ultrasonic wave
generation element (reference example).
[0011]
Embodiments will be described with reference to the drawings. The vehicle presence notification
device notifies presence of a vehicle by a notification sound, and includes a parametric speaker 1
that emits ultrasonic waves formed by ultrasonically modulating a frequency signal forming the
notification sound toward the outside of the vehicle. The ultrasonic speaker 2 for generating an
ultrasonic wave in the parametric speaker 1 is provided for generating an audible sound
generating piezoelectric speaker 3 (sound wave in the audible band) in which the primary
resonance portion (primary component) is present in the audible band. Piezoelectric speaker) is
used. Then, the modulation frequency at which the notification sound is ultrasonically modulated
in the parametric speaker 1 is the sound pressure increasing portion X (the sound pressure rising
by the high-order resonance portion existing in the ultrasonic band of the reproducible frequency
of the audible sound generating piezoelectric speaker 3 Within the range).
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[0012]
A specific example (embodiment) to which the present invention is applied will be described
below 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 above-mentioned "embodiment
of the invention" indicate the same functional objects.
[0013]
[Example 1] A vehicle presence notification device notifies presence of a vehicle by a notification
sound (a single sound, a chord, music, a voice, a pseudo engine sound, etc.). For example, a
vehicle without electricity (internal combustion engine) Automobiles, fuel-cell vehicles etc.),
vehicles with the possibility of stopping the engine while driving and stopping (hybrid vehicles
etc.), vehicles with the possibility of stopping the engine while stopping (eg idle stop vehicles), or
engines Even if it is a vehicle, it is mounted in a conve car etc. whose running noise is quiet.
[0014]
This vehicle presence notification device:-A parametric speaker 1 emitting ultrasonic waves
formed by ultrasonically modulating a frequency signal forming a notification sound, and
emitting it;-Dynamic delivering a notification sound in the audible band directly to the outside of
the vehicle A vehicle horn 4 used as a speaker, and a control circuit 5 for performing operation
control of the ultrasonic speaker 2 and the vehicle horn 4 in the parametric speaker 1 are
configured.
[0015]
(Description of the Parametric Speaker 1) The ultrasonic speaker 2 used for the parametric
speaker 1 generates air vibration of a frequency (20 kHz or higher) higher than the human
audible range, and emits ultrasonic waves toward the front of the vehicle To be installed in the
vehicle.
Specifically, the ultrasonic speaker 2 of this embodiment is provided on the front surface of the
horn 4 for a vehicle (a surface facing the front of the vehicle when the vehicle is mounted: for
example, a spiral horn 28 described later) as shown in FIG. The vehicle horn 4 is attached
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between the front grille 6 and the heat exchanger 7 (radiator or air conditioning heat exchanger,
etc.) so that the ultrasonic radiation direction is directed to the front of the vehicle. The speaker 2
is mounted on a vehicle.
[0016]
As described above, the ultrasonic speaker 2 of this embodiment is provided on the front surface
of the vehicle horn 4 and includes a plurality of piezoelectric speakers 3 for generating ultrasonic
waves, and the plurality of piezoelectric speakers 3 inside. And an ultrasonic speaker housing 11
to be accommodated.
The plurality of piezoelectric speakers 3 are mounted on a support plate 12 fixedly disposed
inside the ultrasonic speaker housing 11, and are collectively arranged as a speaker array as
shown in FIG. 1 (a). Each piezoelectric speaker 3 uses a piezoelectric element (piezoelectric
element) that is expanded and contracted according to an applied voltage (charge and discharge),
and a diaphragm that is driven by the expansion and contraction of the piezoelectric element to
generate compression waves in air. Configured
[0017]
Each piezoelectric speaker 3 mounted on the ultrasonic speaker 2 in this embodiment generates
an acoustic wave in the audible band, not the ultrasonic wave generating element SS {see
reference numeral (a) in FIG. 8} manufactured for ultrasonic wave generation. To generate an
audible sound, and the primary resonance unit (primary resonance frequency: primary
component) is present in the audible band. As a specific example, each piezoelectric speaker 3 in
this embodiment is one that is provided to provide vehicle information to the vehicle occupant by
hearing (voice, warning sound, etc.), The outer diameter size of the piezoelectric speaker 3 used
in this embodiment is compared with the ultrasonic wave generating element SS {see reference
numeral (a) in FIG. 8} manufactured for ultrasonic wave generation so as to be suitable for
generation of audio frequency. Is about twice as large.
[0018]
The piezoelectric speaker 3 of this embodiment is provided to generate an acoustic wave in the
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audible band as described above, and is a sweep signal of sine waves of a predetermined V (volt)
(variable signal from low frequency to high frequency) The frequency characteristic
(reproducible frequency) in the case of giving) is shown in FIG. As shown in FIG. 1 (b), the
primary resonance part (primary component) of the piezoelectric speaker 3 of this embodiment
is present in the audible band (about 2 kHz in this example). This also indicates that the
piezoelectric speaker 3 of this embodiment is provided for generating audible sound.
[0019]
On the other hand, although the piezoelectric speaker 3 of this embodiment is provided for
generating an audible sound as described above, as can be understood from FIG. 1 (b), the highorder resonance portion at about 23 kHz of the ultrasonic band There is a sound pressure rising
portion X by (high-order resonance frequency: specifically, seventh-order resonance portion:
seventh-order component).
[0020]
The ultrasonic speaker housing 11 is provided with ultrasonic radiation ports (openings) for
emitting ultrasonic waves emitted from the respective piezoelectric speakers 3 toward the front
of the vehicle.
The ultrasonic radiation port is provided with a waterproof means for preventing rainwater from
intruding into the mounting portion of each piezoelectric speaker 3. As an example of this
waterproofing means, in this embodiment, an ultrasonic-permeable waterproof sheet 13 covering
the ultrasonic radiation port and a louver 14 disposed on the front surface of the waterproof
sheet 13 are provided {FIG. In the figure, the waterproof sheet 13 and the louver 14 are omitted.
[0021]
(Description of Vehicle Horn 4) As described above, the vehicle horn 4 is fixedly disposed
between the front grille 6 and the heat exchanger 7, and a passenger horn switch (for example, a
steering horn button) Is an electromagnetic horn that generates an audible alarm when it is
operated.
[0022]
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A specific example of the vehicle horn 4 will be described with reference to FIG. 4 (a).
The horn 4 for a vehicle includes: a coil 21 generating a magnetic force when energized; a fixed
iron core 22 (magnetic attraction core) generating a magnetic attraction force by the magnetic
force of the coil 21; and a central portion of a diaphragm 23 (diaphragm) Movable iron core 24
(movable core) supported and supported movably toward fixed iron core 22; · Fixed by moving
movable iron core 24 toward fixed iron core 22 in conjunction with the movement of movable
iron core 24 A movable contact 26 which is separated from the contact 25 and de-energizes the
coil 21;
[0023]
Then, a self-excitation voltage (voltage of 8 V or more) equal to or higher than a threshold value
is applied as a direct current to the conduction terminal (terminal connected to both ends of the
coil 21) of the vehicle horn 4 (i) The movable core 24 is magnetically attracted to the fixed core
22, and the movable contact 26 moves away from the fixed contact 25 to stop the energization
of the coil 21. (ii) The diaphragm 23 moves the action of the return spring by the energization
stop. The movable core 24 is returned to the initial position by being applied to the iron core 24,
and the fixed contact 25 and the movable contact 26 come into contact, and the restoring
operation in which the energization of the coil 21 is resumed is continuously repeated.
[0024]
That is, the fixed contact 25 and the movable contact 26 constitute a current interrupter 27 for
interrupting the conduction circuit of the coil 21.
As described above, the intermittent operation of the coil 21 (intermittent generation of the
magnetic attraction force of the fixed iron core 22) occurs, so that the diaphragm 23 vibrates
together with the movable iron core 24 and the vehicle horn 4 generates an alarm sound.
Concretely, when the self-excitation voltage is continuously given to the horn 4 for vehicles, the
frequency characteristic of the alarm sound which the horn 4 for vehicles generate | occur |
produces is shown to the continuous line A of FIG.
[0025]
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On the other hand, the vehicle horn 4 can be used as a dynamic speaker by providing the coil 21
with a drive signal of a separately excited voltage (for example, a voltage of less than 8 V) lower
than the self-excitation voltage. Alternatively, even if it is a self-excitation voltage, the vehicular
horn 4 is used as a dynamic speaker by quickly controlling the energization of the coil 21 (PWM
control etc.) within a short period of time in which no interruption occurs in the current
interrupter 27. be able to. The frequency characteristic of the vehicle horn 4 when the vehicle
horn 4 is used as a dynamic speaker is shown by a broken line B in FIG. The broken line B is a
frequency characteristic when the sweep signal of a sine wave of 1 V is given to the horn 4 for a
vehicle.
[0026]
In addition, as shown in FIG. 4, the horn 4 for vehicles in this Example reinforces the alarm sound
by the vibration of the diaphragm 23, and radiates | emits it to the vehicle exterior 28 (coil-like
trumpet member: spiral-shaped acoustic pipe However, the present invention is not limited to
this, and other disk-shaped horns or the like which do not use the spiral horn 28 may be used.
[0027]
Here, FIG. 6A shows the arrival range α of the notification sound by the parametric speaker 1
and FIG. 6B shows the arrival range β of the notification sound by the vehicle horn 4.
FIG. 6 shows the reach of the sound pressure of the notification sound of 50 dB. Thus, the
ultrasonic speaker 2 of this embodiment is provided to emit ultrasonic waves toward the front of
the vehicle.
[0028]
Moreover, the horn 4 for vehicles is provided so that a notification sound may reach the
circumference | surroundings of the horn 4 for vehicles substantially equally, seeing a vehicle
from the top. As a specific example, the opening of the spiral horn 28 in the vehicle horn 4 is
mounted toward the lower side of the vehicle (the direction toward the road surface). The
direction of the opening of the spiral horn 28 is not limited to the lower side, and when the
direction is different from the lower side of the vehicle, the radiation direction of the sound wave
is arbitrary (for example, the lower side of the vehicle) You may turn to
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[0029]
(Description of Control Circuit 5) The control circuit 5 mounts the microcomputer chip 5a on the
control board as shown in FIG. 3. For example, as shown in FIG. 4A, the control circuit 5 is a horn
for a vehicle. It is disposed (not limited to) inside 4 (specifically, inside of the horn housing).
[0030]
The control circuit 5 will be specifically described with reference to FIG.
The control circuit 5 determines (a) "whether or not the operating condition of the vehicle
conforms to the condition for generating the notification sound", and (b) the determining unit 31
indicates that the operating condition of the vehicle is notified The notification sound generation
means 32 for generating a “frequency signal forming a notification sound” when it is
determined that the “sound generation condition is met”, and (c) “notification sound output
from the notification sound generation means 32 (D) an ultrasonic drive amplifier 34 for driving
the ultrasonic speaker 2 (a plurality of piezoelectric speakers 3), and (e) a horn 4 for a vehicle.
And a horn drive amplifier 35 for driving the drive. Hereinafter, each means of the above (a) to
(e) mounted on the control circuit 5 will be described.
[0031]
(Description of Determination Means 31) The determination means 31 determines that the
driving state of the vehicle conforms to the generation condition of the notification sound, for
example, when the vehicle travels at a vehicle speed equal to or lower than a predetermined
speed (for example, 20 km / h). , And the notification sound generation means 32 (this is a
specific example and not a limitation).
[0032]
(Description of Notification Sound Generation Means 32) The notification sound generation
means 32 is provided by a notification sound generation program (sound software), and when
the operation instruction is given from the determination means 31, the digital signal Audio
signal)).
[0033]
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(Description of Ultrasonic Modulating Unit 33) The ultrasonic modulating unit 33 is configured
to ultrasonically modulate the "frequency signal forming the notification sound" output from the
notification sound generating unit 32.
As a specific example of the ultrasonic modulation means 33, in this embodiment, the output
signal of the notification sound generation means 32 has a predetermined "ultrasonic frequency
(high-order resonance existing in the ultrasonic band of the reproducible frequency of the
piezoelectric speaker 3) For example, AM modulation (amplitude modulation) is used which
modulates the amplitude change (increase or decrease change of voltage) in the frequency of the
sound pressure increasing portion X by the unit: for example, around 23 kHz).
That is, the "frequency signal forming the notification sound" is modulated to the "ultrasonic
frequency of the sound pressure raising portion X". The ultrasonic modulation unit 33 is not
limited to AM modulation, and PWM modulation is performed to modulate the output signal of
the notification sound generation unit 32 to a predetermined "pulse width change at ultrasonic
frequency (pulse generation time width)". Other ultrasound modulation techniques may be used,
such as (pulse width modulation).
[0034]
A specific example of the ultrasonic wave modulation by the ultrasonic wave modulation means
33 will be described with reference to FIG. For example, it is assumed that the "frequency signal
forming a notification sound" input to the ultrasonic modulation means 33 is the voltage change
shown in FIG. 7A (note that in the figure, a waveform of a single frequency to aid understanding).
Show). On the other hand, the ultrasonic modulation unit 33 includes an oscillation unit that
oscillates at the ultrasonic frequency (the ultrasonic frequency of the sound pressure increasing
portion X) shown in FIG. 7B. The oscillation means may form a predetermined ultrasonic
frequency from the clock signal mounted on the microcomputer chip 5a, or use an oscillator for
ultrasonic modulation independent of the microcomputer chip 5a. Also good.
[0035]
Then, as shown in FIG. 7C, (i) the ultrasonic modulation means 33 increases the amplitude of the
voltage due to the ultrasonic vibration as the signal voltage of the frequency forming “the
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frequency signal forming the notification sound” increases. (Ii) As the signal voltage of the
frequency forming “the frequency signal forming the notification sound” becomes smaller, the
amplitude of the voltage due to the ultrasonic vibration is reduced. In this manner, the ultrasonic
modulation means 33 modulates the "frequency signal forming the notification sound" output
from the notification sound generation means 32 into "amplitude change of oscillation voltage"
of the ultrasonic frequency.
[0036]
(Description of Ultrasonic Drive Amplifier 34) The ultrasonic drive amplifier 34 drives the
ultrasonic speaker 2 based on the ultrasonic signal modulated by the ultrasonic modulation unit
33 (for example, a push-pull power amplifier). By controlling the applied voltage (charging /
discharging state) of each piezoelectric speaker 3, an ultrasonic wave is generated by modulating
“a frequency signal forming a notification sound” from each piezoelectric speaker 3.
[0037]
(Description of Horn Drive Amplifier 35) The horn drive amplifier 35 operates (i) the vehicle
horn 4 as a dynamic speaker while the notification sound generation means 32 generates a
"frequency signal that forms a notification sound". A power amplifier function that amplifies the
frequency signal that forms the notification sound and generates an audible notification sound
from the vehicle horn 4; (ii) applies battery voltage to the vehicle horn 4 while the horn switch is
on And a continuous ON function that generates an alarm sound from the vehicle horn 4.
Note that "horn switch ON" has priority over "report sound generation instruction", and it is
provided so that an alarm sound is always generated from the vehicle horn 4 when the horn
switch is turned on.
[0038]
(Operation of Vehicle Existence Notification Device) When the driving state of the vehicle
conforms to the condition for generating the notification sound, the notification sound
generation means 32 outputs “a frequency signal that forms a notification sound”, and the
ultrasonic speaker 2 outputs the signal shown in FIG. As shown in 2.), an ultrasonic wave (a
sound wave that can not be heard) that is a modulation of the "frequency signal that forms a
notification sound" is emitted toward the front of the vehicle. Then, as shown in FIG. 7D, as the
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ultrasonic wave propagates in the air, the ultrasonic wave having a short wavelength is distorted
and blunted due to the viscosity of the air or the like. As a result, as shown in FIG. 7E, the
amplitude component contained in the ultrasonic wave is self-demodulated in the air on the way
of propagation, and as a result, the "report sound" is reproduced in front of the vehicle. On the
other hand, when the notification sound generation means 32 outputs the "frequency signal
forming the notification sound", the "information notification sound" of the audible sound is
directly emitted from the vehicle horn 4 around the vehicle.
[0039]
(Effects of First Embodiment) As described above, the ultrasonic speaker 2 of this embodiment
uses the piezoelectric speaker 3 provided to generate an acoustic wave in the audible range, and
the piezoelectric for generating an audible sound is used. The ultrasonic wave used for the
parametric speaker 1 can be generated from the speaker 3. The piezoelectric speaker 3 for
generating audible sound is versatile and mass-produced, so that the cost is low. For this reason,
the manufacturing cost of the ultrasonic speaker 2 can be suppressed low, and the cost of the
vehicle presence notification device using the parametric speaker 1 can be suppressed.
[0040]
Second Embodiment Since each piezoelectric speaker 3 mounted on the ultrasonic speaker 2 is
provided for generating an audible sound as described above, it directly emits an acoustic wave
(audio sound) of an audio frequency. Can. Therefore, the control circuit 5 of the second
embodiment generates the "sound wave in the audible band" simultaneously with the
"ultrasound". As a specific example, an ultrasonic signal modulated by the ultrasonic modulation
means 33 and a frequency signal forming a notification sound bypassing the ultrasonic
modulation means 33 may be used. The voltage is given to the drive amplifier 34 to drive each
piezoelectric speaker 3.
[0041]
Thereby, (i) in the directivity range of the parametric speaker 1, it is possible to generate
synthetic sound of "report sound reproduced by the parametric speaker 1" and "report sound
directly emitted as an audible sound from the piezoelectric speaker 3", (Ii) Outside the directivity
range of the parametric speaker 1, only "the notification sound directly emitted as an audible
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sound from the piezoelectric speaker 3" can be generated. As described above, by generating
sound waves in the audible band from each piezoelectric speaker 3, a notification sound can be
generated outside the range of the directivity of the parametric speaker 1.
[0042]
(Another Embodiment 1 of Embodiment 2) Although an example in which “sound waves in the
audible range” are simultaneously released with “ultrasonic waves” has been described
above, “sound waves in the audible range from each piezoelectric speaker 3 according to the
driving state of the vehicle It may be provided to generate (only notification sound). That is,
according to the driving state of the vehicle, (i) generating an ultrasonic wave from each
piezoelectric speaker 3 and generating a notification sound from the parametric speaker 1; (ii)
notifying an audible band from each piezoelectric speaker 3 It is also possible to switch between
an operation state in which sound is directly generated and
[0043]
Third Embodiment Each piezoelectric speaker 3 is not provided to generate an ultrasonic wave as
described above. For this reason, when an ultrasonic wave is generated from the piezoelectric
speaker 3, a resonance sound may be generated in the audible band. Therefore, the vehicle
presence notification device according to the third embodiment simultaneously generates sound
waves of a plurality of frequencies in the audible band from each piezoelectric speaker 3, and the
sound waves of a plurality of frequencies are chords (a plurality of people feel comfortable. It is
provided so as to form a relationship of synthetic waves of sound waves of frequency.
[0044]
If a specific example is disclosed for aiding understanding, when the piezoelectric speaker 3
generates an “AHz resonance sound” in the audible band when generating an ultrasonic wave
from the piezoelectric speaker 3, the vehicle according to the third embodiment exists. The
notification device simultaneously generates “the first auxiliary frequency of BHz” and the
“second auxiliary frequency of CHz” from the piezoelectric speaker 3, and the frequency ratio
of AHz, BHz, and CHz is a chord (Domiso, farad, soshire, etc. ) Is set to the relationship of 4: 5: 6.
[0045]
As described above, even when the piezoelectric speaker 3 generates resonance sound in the
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audible band, the resonance sound is a part of a chord by generating the first auxiliary frequency
and the second auxiliary frequency from the piezoelectric speaker 3. It is possible to alleviate the
discomfort caused by the generation of resonance noise.
[0046]
In the above embodiment, an example is shown in which the piezoelectric speaker 3 for
generating audible sound is used without being touched, but a weight may be added to a part of
the diaphragm, a part of the diaphragm may be cut, etc. The resonance frequency of the
piezoelectric speaker 3 for generating audible sound may be intentionally changed, and the highorder resonance portion (sound pressure increase portion X) existing in the ultrasonic band may
be set to a desired frequency.
[0047]
In the above embodiment, the vehicle presence notification device for generating the notification
sound from the dynamic speaker (the vehicle horn 4 in the embodiment) is shown, but the
notification sound may be generated using only the ultrasonic speaker 2.
[0048]
DESCRIPTION OF SYMBOLS 1 Parametric speaker 2 Ultrasonic speaker 3 Piezoelectric speaker
(piezoelectric speaker for audible sound generation) 5 Control circuit 33 Ultrasonic modulation
means X Sound pressure increasing portion by high-order resonance portion
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