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JPH11262084

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DESCRIPTION JPH11262084
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker apparatus for reproducing sound using an ultrasonic wave generating element and an
audio signal transmitting apparatus using the ultrasonic wave generating element.
[0002]
2. Description of the Related Art Conventionally, as a speaker device, one configured to vibrate a
diaphragm and to listen to sound emitted from the diaphragm into the air has been widely used.
This type of speaker device vibrates a diaphragm by an audio signal of an audible frequency
range of about 20 Hz to 20 KHz, and emits sound directly from the diaphragm into air.
[0003]
By the way, in a speaker device in which the diaphragm is driven by an audio signal in the
audible band, sound is emitted with a spread in the air centering on the diaphragm. This type of
speaker device is useful for emitting sound to a wide space.
[0004]
However, with this type of speaker device, it is not possible to emit sound only to a specific
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1
listener.
[0005]
Also, in order to make it possible for only an individual to listen to the reproduced sound,
headphones and earphones worn on the head and pinna are used.
This type of headphones and earphones also drive the diaphragm with audio signals in the
audible band, and the sound is emitted with a spread in the air centered on the diaphragm.
Headphones and earphones need to be attached to the head and pinnacle while the speaker unit
is sealed in order to ensure secrecy.
[0006]
Therefore, an object of the present invention is to provide a speaker device capable of emitting
sound with superdirectivity by using a novel driving method.
[0007]
Another object of the present invention is to provide a speaker device capable of emitting sound
with a secret speech function.
[0008]
Still another object of the present invention is to provide a speaker device capable of
simultaneously listening to different sounds at a plurality of positions.
[0009]
Still another object of the present invention is to provide a speaker device capable of setting
sound image localization at a free position.
[0010]
A speaker device according to the present invention proposed to achieve the above-mentioned
object is a signal of a frequency band higher than at least an audible band by an audio signal
output from a sound source by modulation means. The ultrasonic wave generation element is
driven by the frequency-modulated signal from the modulation means.
08-05-2019
2
[0011]
Here, the modulation means converts the audio signal output from the sound source into a signal
modulated to a first frequency and a signal modulated to a second frequency different from the
first frequency.
At this time, a frequency component corresponding to the difference between the ultrasonic
wave of the first frequency and the ultrasonic wave of the second frequency emitted from the
ultrasonic wave generation element is heard as an audible sound.
[0012]
A speaker device according to the present invention includes, for example, a first element group
in which an ultrasonic wave generating element is arranged in a ring shape and a second element
group in which a ultrasonic element is arranged in a ring shape on the outer peripheral side of
the first element group. The signal frequency-modulated to the first frequency is input to the first
element group, and the signal frequency-modulated to the second frequency is input to the
second element group.
[0013]
In the speaker device according to the present invention, the signal frequency-modulated to the
first frequency and the signal frequency-modulated to the second frequency from the modulation
means are mixed by the mixing means and input to the ultrasonic wave generation element.
[0014]
Further, the speaker device according to the present invention is provided with differentiating
means for differentiating the audio signal output from the sound source before the frequency
modulation to the signal in the frequency band higher than the audible band by the modulation
means.
Furthermore, the speaker device is provided with a DC offset means for level shifting the audio
signal differentiated by the differentiating means.
08-05-2019
3
[0015]
Furthermore, the speaker device according to the present invention performs inverse cosine
function processing on the audio signal output from the sound source.
[0016]
Furthermore, the speaker apparatus according to the present invention comprises amplitude
modulation means for amplitude modulating an audio signal output from a sound source to a
signal frequency-modulated to a signal in a frequency band higher than at least an audible band
and amplitude modulating an audio signal. .
At this time, the audio signal output from the sound source is subjected to inverse cosine
function processing.
[0017]
And, means is provided for correcting the frequency characteristics of the ultrasonic wave
emitted from the ultrasonic wave generation element.
[0018]
In addition, a correction unit is provided to correct in advance the frequency characteristics of
the audio signal output from the sound source.
[0019]
Furthermore, according to the present invention, the audio signal output from the sound source
is modulated by the modulation means into a signal of a frequency band higher than the audible
band, and the ultrasonic wave generation element is driven by the frequency-modulated signal
from the modulation means It is an audio signal transmission device that collects sounds in the
audible band due to the difference frequency distortion of ultrasonic waves emitted from the
generating element with a microphone, and performs inverse cosine function processing on the
collected audible band signals.
[0020]
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4
BEST MODE FOR CARRYING OUT THE INVENTION A loudspeaker apparatus according to the
present invention and an audio signal transmission apparatus using the loudspeaker apparatus
will be described below.
[0021]
The basic configuration of the speaker device according to the present invention will be
described with reference to FIG.
This speaker apparatus, as shown in FIG. 1, comprises a carrier wave oscillator 1 outputting a
carrier wave of a constant frequency, an audio signal source 2 outputting an audio signal, and an
audio signal from the audio signal source 2 And a frequency modulated carrier wave output from
the frequency modulator 3 (hereinafter referred to as a frequency modulated signal).
The ultrasonic wave generator 5 driven by.
[0022]
The carrier oscillator 1 supplies a carrier of a constant frequency, for example, a carrier of 40
KHz to the frequency modulator 3.
The audio signal source 2 includes, for example, an optical disk player and a tape recorder, and
supplies an audio signal as a modulation signal to the frequency modulator 3.
The frequency modulator 3 frequency modulates the carrier wave input from the carrier wave
oscillator 1 with the modulation signal from the audio signal source 2.
The frequency modulation signal is input to the ultrasonic generator 5 via the amplifier 4.
The ultrasonic wave generator 5 comprises, for example, at least one ultrasonic wave generating
element, and has a very high directivity (hereinafter referred to as superdirectivity).
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5
And is driven by the frequency modulation signal amplified by the amplifier 4 to emit ultrasonic
waves based on the frequency modulation signal with superdirectivity in the direction in which
the ultrasonic wave generator 5 is directed.
Then, the user can hear the sound corresponding to the audio signal from the audio signal source
2 when the ultrasonic wave generator 5 is directed.
In addition, the user can feel that, for example, when the ultrasonic wave generator 5 is directed
to the wall, a noise is being emitted from the wall.
[0023]
Here, when ultrasonic waves are emitted based on a frequency modulation signal frequencymodulated with an audio signal from the audio signal source 2, a basic principle in which a sound
corresponding to the original audio signal can be heard will be briefly described.
[0024]
As shown in the first equation, if there is even-order non-linearity in the system, and a signal
including two frequency (w1 / 2?, w2 / 2?) components as shown in the second equation is
input to the system, As shown in Equation 3, differential frequency distortion, which is a type of
intermodulation distortion, occurs.
[0025]
y = Ax + Bx2 Formula 1 Here, x is an input signal of a system, y is an output signal of a system.
[0026]
x = f 1 cos ? 1 t + f 2 cos ? 2 t When the second equation is input to the first equation, the third
equation is obtained.
[0027]
y = A (f 1 cos ? 1 t + f 2 cos ? 2 t) + B / 2 (f 12 + f 22) + B / 2 (f 12 cos 2 ? 1 t + f 22 cos 2 ?
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2 t) + B (f 1 f 2 cos (w 1-w 2) t) + B (f 1 f 2 cos (w 1 + w 2) t) The second term is a direct current
component, the third term is a second harmonic component, the fourth term is a difference
frequency component, and the fifth term is a sum frequency component.
The difference frequency component of the fourth term is a difference frequency distortion, and
a frequency component (difference sound) corresponding to the frequency difference (w1?w2)
appears at the output of the system.
Specifically, for example, when 40 kHz and 41 kHz sine wave signals output from two carrier
wave oscillators are mixed to drive the ultrasonic wave generator, a 1 kHz difference tone
corresponding to the difference frequency distortion is heard.
[0028]
By the way, as widely known, in frequency modulation, a frequency modulation signal includes
an infinite number of sidebands centered on a carrier.
Thus, if the air has even-order non-linearities as described above for ultrasound, the original
audio signal is reproduced and the user can hear the corresponding sound.
[0029]
Next, a specific configuration of the speaker device according to the present invention having the
above-described basic configuration will be described with reference to FIG.
[0030]
In addition, the same code | symbol is attached | subjected to the circuit which has the same
function as the circuit which comprises the speaker apparatus shown in FIG. 1, and description
about those details is abbreviate | omitted.
[0031]
As shown in FIG. 2, this speaker device includes first and second carrier oscillators 1a and 1b for
outputting carrier waves of a constant frequency, an audio signal source 2 for outputting an
audio signal, and first and second First and second frequency modulators 3a and 3b for
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respectively frequency-modulating the carrier waves from the carrier wave oscillators 1a and 1b
with the audio signal from the sound source 1 and the inverted audio signal, and the first and
second frequency modulations The first and second ultrasonic generators 5a and 5b are
respectively driven by the frequency modulation signals output from the units 3a and 3b.
[0032]
The first and second carrier oscillators 1a and 1b respectively supply, for example, a 40 KHz
carrier to the first and second frequency modulators 3a and 3b.
The audio signal source 2 uses the audio signal as a modulation signal and supplies it to the
frequency modulator 3a via the first amplifier 12a and also to the inverting circuit 11.
The inverting circuit 11 inverts the amplitude of the audio signal from the audio signal source 2
and supplies the inverted signal to the second frequency modulator 3b via the second amplifier
12b.
The first and second frequency modulators 3a and 3b are the modulated signals amplified by the
first and second amplifiers 3a and 3b, respectively, and the frequencies of the carriers input from
the first and second carrier oscillators 1a and 1b, respectively. Modulate.
The obtained frequency modulation signal is input to the first and second high pass filters 13a
and 13b having a cutoff frequency of 20 KHz, for example, where components of 20 KHz or less
are removed, and the first and second amplifiers 4a and 4b are used. The first and second
ultrasonic wave generators 5a and 5b are input. The first and second ultrasonic wave generators
5a and 5b are composed of, for example, at least one ultrasonic wave generating element, and
are driven by frequency modulation signals amplified by the first and second amplifiers 4a and
4b, respectively. As a result, ultrasonic waves based on the frequency modulation signal are
emitted with superdirectivity in the direction in which the first and second ultrasonic wave
generators 5a and 5b are directed.
[0033]
Here, the specific structure of the first and second ultrasonic wave generators 5a and 5b will be
described.
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[0034]
Each of the first and second ultrasonic wave generators 5a and 5b is composed of a plurality of,
for example, 37 piezoelectric elements 50, which are ultrasonic wave generating elements, and,
for example, as shown in FIG. The piezoelectric elements 50 of the ultrasonic wave generator 5a
are disposed in a ring shape on the inner circumferential side, and the second ultrasonic wave
generator is formed in a ring shape so as to surround the piezoelectric elements 50 of the first
ultrasonic wave generator 5a. The piezoelectric element 50 of 5b is disposed.
At this time, the piezoelectric elements 50 of the first ultrasonic wave generator 5a disposed in
the ring shape on the inner peripheral side and the piezoelectric elements 50 of the second
ultrasonic wave generator 5b disposed in the ring shape on the outer peripheral side. The groups
are arranged coaxially.
[0035]
The user can hear the sound corresponding to the audio signal from the audio signal source 2
when the supersonic 1st and 2nd ultrasonic wave generators 5a and 5b are directed in this way. .
By the way, in this speaker device, since the first and second ultrasonic wave generators 5a and
5b are driven by two frequency modulation signals respectively frequency-modulated by an
audio signal and an audio signal whose polarity is inverted, That is, since the ultrasonic waves
are emitted differentially, the user can hear a louder sound than the speaker device shown in FIG.
Furthermore, the sound pressure level can be increased by using a plurality of piezoelectric
element 50 groups.
[0036]
In the above-described speaker device, two groups of piezoelectric elements 50 are used,
respectively, but after mixing frequency modulation signals using a mixer, the mixed signals
drive one group of piezoelectric elements 50. You may
[0037]
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9
In this case, a plurality of, for example, 73 cylindrical piezoelectric elements 50 are used, and the
piezoelectric elements 50 are concentrated so as to be in close contact with each other as shown
in FIG. 4, for example.
In the speaker apparatus using the ultrasonic wave generator 5 having a configuration in which
the plurality of piezoelectric elements 50 are arranged in a concentrated manner, the directivity
characteristic at a position 0.5 m away from the speaker apparatus is, for example, as shown by
A in FIG. The directivity characteristics at a distance of 1 m show the characteristics as shown by
B in FIG. 5, and the directivity characteristics at a distance of 2 m show characteristics as shown
by C in FIG. It has extremely high directivity in the front direction of the device.
[0038]
The ultrasonic wave generator 5 shown in FIG. 4 combines a plurality of ultrasonic wave
generating elements (piezoelectric elements 50) into several groups, and inputs and drives a
frequency modulation signal for each ultrasonic wave generating element of each group. You
may do so. In this case, by combining a plurality of ultrasonic wave generating elements into two
groups, it can be used as the ultrasonic wave generator 5a, 5b of the speaker apparatus shown in
FIG. 2 described above.
[0039]
Next, another specific example of the speaker device to which the present invention is applied
will be described with reference to FIG. The circuits having the same functions as those of the
circuit shown in FIG. 2 described above are denoted by the same reference numerals, and the
description thereof will be omitted.
[0040]
As shown in FIG. 6, this speaker device is provided with first and second carrier oscillators 1a
and 1b for outputting carrier waves of constant frequency, an audio signal source 2 for
outputting an audio signal, and an output from the audio signal source 2 And an amplifier 23a
for adding an offset voltage to the differentiated signal output from the differentiator 22, and
inverting the polarity of the differentiated signal output from the differentiator 22 and adding an
offset voltage First and second frequency modulators 3a for frequency-modulating the carrier
waves from the inverting amplifier 23b and the first and second carrier oscillators 1a and 1b
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10
respectively with the differential signal from the amplifier 23a and the differential signal from
the inverting amplifier 23b , 3b, and a mixer 24 for mixing the frequency modulation signals
output from the first and second frequency modulators 3a, 3b. Comprises a correction filter 26
for suppressing a predetermined frequency component of the mixed frequency-modulated signal
from the mixer 24, the ultrasonic generator 5 driven by the frequency modulated signal output
from the correction filter 26.
[0041]
The first and second carrier oscillators 1a and 1b respectively supply, for example, a 40 KHz
carrier to the first and second frequency modulators 3a and 3b.
The audio signal source 2 supplies the audio signal to the differentiator 22 through the amplifier
21. The differentiator 22 differentiates the audio signal amplified by the amplifier 21 and
supplies the obtained differentiated signal to the amplifier 23a and the inverting amplifier 23b.
The amplifier 23a adds an offset voltage to shift the DC level of the differential signal from the
differentiator 22, and supplies it as a modulation signal to the first frequency modulator 3a.
Meanwhile, the inverting amplifier 23b inverts the polarity of the differential signal from the
differentiator 22, adds an offset voltage to shift the DC level, and supplies it as a modulation
signal to the second frequency modulator 3b. The first and second frequency modulators 3a and
3b respectively modulate the frequency of the carrier wave input from the first and second
carrier oscillators 1a and 1b with modulation signals whose direct current level is shifted by the
amplifier 23a and the inverting amplifier 23b. Do. The obtained frequency modulation signal is
input to the mixer 24. The mixer 24 mixes these two frequency modulation signals and supplies
them to a high pass filter 25 having a cutoff frequency of 20 KHz, for example. The high pass
filter 25 removes the component of 20 KHz or less of the mixed signal output from the mixer 24
and supplies it to the correction filter 26.
[0042]
By the way, the ultrasonic generator 5 has a frequency of mechanical resonance, for example,
around 40 KHz, and its frequency characteristic is not flat. Therefore, the correction filter 26
suppresses a predetermined frequency component of the frequency modulation signal from the
high pass filter 25, that is, a component around 40 KHz, and the frequency modulation signal
whose resonance frequency component is suppressed is transmitted through the amplifier 27 to
the ultrasonic wave generator. Supply to 5. The ultrasonic wave generator 5 comprises, for
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11
example, at least one ultrasonic wave generation element, and is driven by the frequency
modulation signal amplified by the amplifier 27 to generate an ultrasonic wave based on the
frequency modulation signal, the ultrasonic wave generator 5 It emits with super directivity in
the direction to which
[0043]
Here, the principle of hearing the sound with this speaker device will be briefly described.
[0044]
A signal O (t) obtained by mixing two frequency modulation signals is represented by the fourth
equation shown below.
[0045]
O (t) = Accos (?ct + ?c + kch (t) dt) + Bc cos (?c?t + ?c ? + k??h (t) dt) Equation 4 The
second-order distortion of this signal O (t) is given by It is expressed by equation 5.
[0046]
O (t) 2 = Ac2 cos2 (.omega.ct + .theta.c + k?h (t) dt) + Bc2 cos2 (.omega.c't + .theta.c '+ k'?h (t)
dt) + AcBc cos ((. Omega.c + .omega.c') t + (. Theta.c + .theta.c ') + (k + k') @ h (h) t) d + Ac B c cos
((? c ?? c ?) t + (? c ?? c ?) + (k k ?) ?h (t) d The first to third terms of the fifth equation
are direct currents, 2? c, It is a sideband wave centered on 2?c ? and (?c + ?c ?).
The fourth term is a sideband centered at (.omega.c -.omega.c '), which is in the audible band, i.e.
a signal that humans hear.
Therefore, when the fourth term is equal to the original audio signal s (t), that is, when the sixth
equation holds, the audio signal can be heard.
[0047]
AcB c cos (??ct + ??c + ?k?h (t) dt) = s (t) Equation 6, where | s (t) | ? 1, ??c = ?c??c
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?, ??c = ?c??c ?, ?k = k?k ? is there.
In order to simplify Equation 6, hereinafter, s (t) normalized with AcBc is newly defined as s (t).
[0048]
The seventh equation is obtained by solving the sixth equation for h (t).
[0049]
h (t) = [d / dt {cos-1s (t)}-??c] / ?k Equation 7 The carrier wave may be frequency-modulated
by the signal h (t) obtained according to this equation 7, ie, an audio signal Listening to the
sound corresponding to the original audio signal by subjecting the audio signal from source 2 to
inverse cosine function processing, giving a DC offset, differentiating the obtained signal, and
frequency-modulating the carrier with this differentiated signal Can.
[0050]
By the way, when s (t) is sufficiently small, cos-1s (t) in the seventh equation can be
approximated to ? / 2-s (t) by series expansion, and the signal h (t) is It can be expressed by the
eighth equation.
[0051]
h (t) ? [d / dt {-s (t)}-??c] / ?k Eq. 8 And, with this speaker device, the signal processing
corresponding to Eq. It is done in 23b.
[0052]
Next, still another specific example of the speaker device to which the present invention is
applied will be described with reference to FIG.
[0053]
As shown in FIG. 7, this speaker apparatus has one carrier oscillator 1a, 1b of the speaker
apparatus shown in FIG. 6 described above, and also has amplitude modulators 28a, 28b at the
subsequent stage of the frequency modulators 3a, 3b, A preprocessing circuit 30 is added to the
front stage.
08-05-2019
13
Therefore, circuits having the same functions as those of the circuit shown in FIG. 6 are denoted
by the same reference numerals, and the description thereof will be omitted.
[0054]
These added amplitude modulators 28a and 28b use an audio signal subjected to signal
processing to be described later by the pre-processing circuit 30 as a modulation signal, and a
frequency modulation signal from the frequency modulators 3a and 3b as a carrier as their
carrier waves. Are modulated with the modulation signal, and the obtained amplitude modulation
signal is supplied to the mixer 24.
[0055]
Here, the principle of hearing the sound with this speaker device will be briefly described.
[0056]
If the condition that Ac = Bc = Ac ? / 2, ??c = ?c??c ? = 0, ??c = ?c??c ? = 0, k ? = 0
is added to the above-described fourth equation, the fourth equation described above Can be
transformed into the following ninth equation.
[0057]
O (t) = [Ac ? + Ac ? {? 1 + cos ((k / 2) ?h (t) dt)] О cos (?ct + ?c + (k / 2) ?h (t) dt) The
amplitude modulation in which (t) is a modulation signal is expressed by the following equation
10.
[0058]
[y (t)] AM = (Ac + ? (t)) cos (?ct + ?c) In the equation 10, when the equation 11 is satisfied, the
same signal as the equation 9 is obtained.
[0059]
? (t) = Ac ? {? 1 + cos ((k / 2) ?h (t) dt)} = Ac ? {? 1 + cos ((1/2) cos?1s (t))} Equation 11
Therefore, In the speaker device, the preprocessing circuit 30 comprises, for example, a digital
signal processor (DSP) and a memory storing instructions and data for operating the DSP. The
08-05-2019
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DSP is, for example, as shown in FIG. An inverse cosine function operation unit 31 for obtaining a
value, a multiplication unit 32 which halves the output of the inverse cosine function operation
unit 31, and a cosine function operation unit 33 for obtaining a cosine value of the output of the
multiplication unit 32, Execute signal processing corresponding to the equation.
That is, the inverse cosine function operation unit 31 performs inverse cosine function
processing on the audio signal from the audio signal source 2, the multiplication unit 32 halves
the obtained result, and the cosine function operation unit 33 Find the cosine value of 32
outputs.
[0060]
By the way, the second term of Formula 11 can be modified as shown in Formula 12.
[0061]
cos ((1/2) cos-1s (t)) = ((1 + s (t)) / 2) 1/2 equation 12 Therefore, as shown in FIG. 10, for
example, the pre-processing circuit 30 generates an audio signal. A direct current offset adding
unit 34 for giving a direct current offset, a multiplying unit 35 which halves the output of the
direct current offset adding unit 34, and a square root operation unit 36 for obtaining a square
root of the output of the multiplying unit 35 Can.
By configuring the pre-processing circuit 30 in this way, the DSP does not need to perform
arithmetic processing for obtaining a cosine function and an inverse cosine function, and
processing for computing one square root may be performed. Memory capacity can be reduced.
In addition, when the arithmetic processing is performed by hardware, the circuit scale can be
reduced.
[0062]
Further, the operation of halving only has the effect of changing the amplitude of the modulation
output, and thus can be omitted. That is, the pre-processing circuit 30 gives a direct current
offset to the audio signal as shown in FIG. A direct current offset adding unit 34 and a square
08-05-2019
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root operation unit 36 for obtaining a square root of the output of the direct current offset
adding unit 34 can be configured.
By configuring the pre-processing circuit 30 in this way, the DSP does not need to perform
arithmetic processing for obtaining a cosine function and an inverse cosine function, and
processing for computing one square root may be performed. Memory capacity can be reduced.
In addition, when the arithmetic processing is performed by hardware, the circuit scale can be
reduced.
[0063]
Also, in the above-described specific speaker device, the ultrasonic wave generator 5 is driven by
the frequency modulation signal obtained by frequency-modulating the carrier wave with the
audio signal. However, the ultrasonic wave generator 5 As described above, for example, it
comprises a plurality of piezoelectric elements.
Therefore, the correction filter 26 may be provided in the front stage of each piezoelectric
element so that desired frequency characteristics and directivity can be obtained as the entire
ultrasonic wave generator.
Furthermore, the amplifier 4 shown in FIGS. 1 and 2 and the amplifier 27 shown in FIGS. 6 and 7
may be included to obtain desired frequency characteristics and directivity.
Furthermore, correction processing for obtaining this desired frequency characteristic may be
performed at the stage of the audio signal.
[0064]
Furthermore, two of the above-described speaker devices may be provided, and separate audio
signals may be input to the respective speaker devices, and filters having different frequency
characteristics and phase characteristics may be provided in front of the piezoelectric elements
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of the respective speaker devices.
In this case, for example, sounds can be emitted from the same position with directivity different
from each other, and sounds that are heard can be differentiated depending on the position of
the listener.
[0065]
Since the speaker device according to the present invention has extremely high directivity, it can
provide audio information to a specific position.
[0066]
Therefore, it is possible to configure an audio signal transmission apparatus provided with a
confidential function without using a transmission connection line or the like of an audio signal.
[0067]
For example, as shown in FIG. 8, the audio signal transmitting apparatus includes an audio signal
source 41 for outputting an audio signal, a pre-processor 42 for frequency modulating a carrier
wave with a signal obtained by differentiating the audio signal, and a frequency from the preprocessor 42. The system includes an ultrasonic wave generator 44 driven by a modulation
signal, a microphone 45 in the audible range, and a post processor 46 that performs inverse
cosine function processing on the signal from the microphone 45.
[0068]
The pre-processor 42 comprises, for example, the amplifier 21 to the correction filter 26
constituting the speaker apparatus shown in FIG. 6 described above, and is a frequency
modulation signal obtained by frequency-modulating a carrier wave with an audio signal. The
generator 44 is driven.
Therefore, among the sound waves emitted from the ultrasonic wave generator 44, the sound
that can be heard by humans due to the difference frequency distortion is represented by the
fourth term of the fifth formula described above, ie, the twelfth formula shown below.
08-05-2019
17
[0069]
y (t) = cos (.DELTA..omega.ct + .DELTA..theta.c + .DELTA.k.noteq.h (t) dt) Since the equation 12
microphone 45 detects sound in the audible range, it outputs the signal y (t) represented by this
equation 12. .
The post processor 46 performs signal processing corresponding to equation 13 to restore the
original audio signal h (t).
[0070]
kh (t) = [d / dt {cos-1y (t)}-?? c Equation 13 And, when the user reproduces the signal output
from the post processor 46 using, for example, headphones, the original audio You can hear the
sound corresponding to the signal.
By the way, a third party located between the ultrasonic wave generator 44 and the microphone
45 has a large distortion and can not understand the content of the sound.
Also, third parties who are not pointed at the ultrasound generator 44, ie outside the directivity
range, can not hear the sound. Therefore, in this audio signal transmission device, the content of
the audio signal is not intercepted by a third party.
[0071]
Here, a specific example of the correction process for obtaining the above-described desired
frequency characteristic will be described.
[0072]
For example, in the speaker apparatus shown in FIG. 7, after frequency modulation with an audio
signal, the signal is amplitude-modulated with the output of the pre-processing circuit 30, so
assuming that the modulation degree is the same, the frequency modulators 3a and 3b Output
(hereinafter, simply referred to as modulator output.
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H) (t) can be expressed by equation 14, and the outputs g (t) of the amplitude modulators 28a
and 28b can be expressed by equation 15.
[0073]
h (t) = cos ((1/2) cos-1s (t)) equation 14 g (t) = h (t) cos (?ct + ?) equation 15 In equation 14,
the modulation degree is the same. Then, since the sum of the modulation degrees is 0, the
frequency modulation term in the cosine function disappears, and only the amplitude modulation
is performed as a whole of the fifteenth equation.
[0074]
Assuming that the Fourier transform of h (t) which is the output of the pre-processing circuit 30
is H (?) as shown in equation 16, the modulation output g (t) expressed by equation 15 is H (?)
It becomes like a 17th type using.
[0076]
G (?) = (H (? + ?c) + H (?-?c)) Equation 17 Further, the square distortion g 2 (t) of the signal
g (t) and its Fourier transform are expressed by Equations 18 and 19 Be done.
[0077]
g2 (t) = (g (t)) 2 equation 18
[0079]
Here, H (?) is band-limited at the angular frequency ?s and is mainly distributed in the audio
band as shown in Eqs. 20 and 21, and the center frequency of modulation is ?s H (?) = 0 Eq. 20
?c> 2?s Equation 21 Hc иии H (и) ? 0 Equation 22 The conditions for the equation (22) are as
follows.
[0080]
H (k + .omega.c) H (.omega.-k + .omega.c) -2.omega.c-2.omega.s.ltoreq..omega..ltoreq.-2.omega.c +
2.omega.sH (k-.omega.c) H (.omega.-k-.omega.c) + 2.omega.c2.omega.s.ltoreq..omega..ltoreq.2.omega.c + 2.omega.s H (k + .omega.c) H (.omega.-k-.omega.c)
?2?s ? ? ? + 2?s H (k??c) H (??k + ?c) ?2?s ? ? ? + 2?s And, since the object to
be dealt with here is the audio band component (difference frequency) of square distortion,
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Ignoring the first two terms whose components are distributed in the ultrasonic band (▒
2?c?2?s ? ? ? ▒ 2?c + 2?s), the last of which the components are distributed in the
audible band (?2?s ? ? ? + 2?s) Focusing on only the second term, Equation 23 is obtained.
[0082]
The outputs g (t) of the amplitude modulators 28a and 28b are emitted from the ultrasonic
generator 5 with the same characteristics, and an audio signal based on the difference frequency
component of the square distortion generated in the air Although it is ideal to match, in reality,
the sound corresponding to the signal g (t) is not generated due to the characteristics of the
ultrasonic wave generator 5 and the amplifier 27 in the previous stage.
Here, a characteristic that changes the characteristic of the signal g (t) is referred to as a speaker
characteristic a (t).
[0083]
The speaker output, that is, the output x (t) of the ultrasonic wave generator 5 is expressed by
the convolution of the signal g (t) and the speaker characteristic a (t) as shown in Equations 24
and 25.
[0084]
x (t) = a (t) * g (t) Equation 24 X (?) = A (?) G (?) Equation 25 Note that * indicates a
convolution operation.
[0085]
In order to eliminate the influence of the speaker characteristic a (t) in the speaker output X (?)
of Expression 25, the characteristic is opposite to that of the speaker characteristic a (t) at least
in the band in which the modulator output G (?) is distributed. A filter may be added to the front
stage of the speaker.
Specifically, for example, as shown in FIG. 12, a correction filter 26 having a characteristic
08-05-2019
20
reverse to the characteristic of the ultrasonic wave generator 5 is inserted into the output of the
amplitude modulator 28, and the ultrasonic wave generator 5 is Input the signal shown in
equation 26.
[0086]
Ga (?) = A?1 (?) G (?) Formula 26 Here, a specific example will be described in which the
correction processing for obtaining a desired frequency characteristic is performed at the stage
of the audio signal.
[0087]
If the component of the audio band of the square distortion x 2 (t) is obtained using the condition
such as | ? | ? 2?s, as in the case of the expansion of G 2 (?) shown in the 19th equation, the
28th equation is obtained .
[0088]
x 2 (t) = (x 2 (t)) 2 equation 27
[0090]
The flow of the expansion of the equation 27 can be simply described as follows: ?The effect of
modulating the signal H (k) centering on ?c is moved to the equation of the speaker
characteristic A (k)?.
The speaker characteristics A (k??c) and A (k + ?c) in Expression 28 correspond to the
speaker characteristics having a modulation effect.
[0091]
As shown in FIG. 14 (C), the speaker characteristics have non-flat power characteristics with a
peak at the modulation angular frequency ▒ ?c.
Moreover, the characteristics have different curves on either side of the peak.
08-05-2019
21
The characteristics shown in FIG. 14C simply simulate the characteristics of a general ultrasonic
piezoelectric element, but when the power is displayed in decibels, the characteristics have an
approximately linear slope.
[0092]
In order to correct such asymmetrical speaker characteristics in the audio band, ie, the output of
the pre-processing circuit 30 as shown in FIG. 13, for example, as shown in FIG. It needs to be
corrected.
To realize this simply: Select a piezoelectric element with symmetrical power curves on both
sides of the modulation frequency (carrier frequency).
? Modulation processing or subsequent correction to ensure symmetry.
The method such as
[0093]
The correction for securing the symmetry in the modulation process or the latter stage is to
satisfy the equation 29, and the equation 30 is established.
[0094]
A (k-.omega.c) = A (k + .omega.c) Equation 29 A (k-.omega.c) A (.omega.-k + .omega.c) + A (k +
.omega.c) A (.omega.-k-.omega.c) = 2A (k + .omega.c) A (.omega.-k + .omega.c) Expression 30 and
Expression 28 showing the square distortion of the speaker output can be transformed into
Expression 31, and the speaker characteristic A (k) is processed together with the input signal H
(k) of the amplitude modulator 28. be able to.
[0096]
08-05-2019
22
Accordingly, H (?) is multiplied by the inverse characteristic A-1 (k + ?c) in the band of | k | ?
?s of the speaker characteristic A (k + ?c) converted to be distributed in the audio band, and
The new Ha (?) obtained in the above is the input of the amplitude modulator 28.
Specifically, for example, as shown in FIG. 13, the correction filter 29 having the abovementioned inverse characteristic A-1 (k + ?c) is provided between the pre-processing circuit 30
and the amplitude modulator.
[0097]
Next, some examples to which the above-described speaker apparatus according to the present
invention is applied will be described.
[0098]
FIG. 15 shows an ultrasonic wave generator 61 in which a plurality of piezoelectric elements 50
of the speaker device according to the present invention are combined with a rearview mirror 60
mounted in a car.
At this time, the ultrasonic wave generator 61 has a plurality of piezoelectric elements 50
arranged in two rows along the lower side edge of the rearview mirror 60.
[0099]
Since the rearview mirror 60 of a car is generally directed in the direction of the driver 62, the
ultrasonic generator 61 can be directed to the driver 62 to drive the ultrasonic waves emitted
from the ultrasonic generator 61. It is possible to concentrate on the person 62 and allow only
the driver 62 to listen to the sound.
Therefore, it can be set as the speaker apparatus which makes only the driver 62 listen to the
required audio information.
[0100]
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23
In addition, since the ultrasonic wave emitted from the ultrasonic wave generator 61 has high
directivity, by providing the microphone 63 in a part of the room mirror 60, the voice input /
output device of the handsfree communication device may be configured. it can.
At this time, since the ultrasonic wave emitted from the ultrasonic wave generator 61 has
extremely high directivity, even if the microphone 63 is disposed in the vicinity of the ultrasonic
wave wave generator 61, the ultrasonic wave emitted from the ultrasonic wave generator 61 Is
not input to the microphone 63 and does not cause howling.
Further, since the ultrasonic waves emitted from the ultrasonic wave generator 61 are
concentrated on the driver 62, it is possible to prevent the audio information from being listened
to by the passenger 64, and at least the secrecy of the audio information on the receiving side.
Can be secured.
[0101]
Moreover, while combining each piezoelectric element 50 which comprises the ultrasonic wave
generator 61 so that several sets may be comprised, a filter is provided in the front stage of the
piezoelectric element 50 which comprises each set, The frequency of the piezoelectric element
50 of each set By making the characteristics and the phase characteristics different, it is possible
to align the wave fronts of the ultrasonic waves emitted from the piezoelectric elements 50 of
each set in a specific direction, and the driver 62 and the passenger 64 hear different voices and
tones. It can be done.
[0102]
Further, FIG. 16 shows an example in which the speaker device according to the present
invention is applied to a conference system.
In this conference system, a plurality of ultrasonic wave generators 72 and microphones 73 in
which a plurality of piezoelectric elements 50 are combined are arranged on a conference table
71 as a pair at regular intervals.
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24
By arranging the plurality of ultrasonic wave generators 72 in this manner, the audio information
emitted from each ultrasonic wave generator 72 can be concentrated on the listener 74 opposed
to each ultrasonic wave generator 72. In the case where the listener 74 has different information,
for example, the mother language of the listener is different, information of different languages
may be provided to the listeners 74 who are adjacent to each other.
[0103]
Furthermore, FIG. 17 shows an example in which the speaker device according to the present
invention is applied to a television type telephone device. In this television type telephone
apparatus, an ultrasonic wave generator 82 in which a plurality of piezoelectric elements 50 are
combined and a microphone 83 are disposed on the top of a receiver 81. Since the ultrasonic
waves emitted from the ultrasonic wave generator 82 have extremely high directivity, the
ultrasonic wave generator 82 is directed to the user 84, and even if the microphone 83 is
disposed in the vicinity of the ultrasonic wave generator 82, the ultrasonic wave is generated.
The ultrasonic sound emitted from the generator 82 is not input to the microphone 83 and does
not cause howling, and a hands-free voice input / output device can be configured.
[0104]
Furthermore, FIG. 18 shows an example in which the speaker device according to the present
invention is applied to an acoustic device incorporated in a vehicle such as an airplane or a bus.
An ultrasonic wave generator 91 in which a plurality of piezoelectric elements 50 of the speaker
device constituting the acoustic device are combined is disposed to be directed to a listener 93
who sits on each seat 92. By arranging the ultrasonic wave generator 91 in this manner, audio
information can be provided only to the desired listener 93 without using a secrecy type
headphone or the like.
[0105]
Next, FIG. 19 shows an example in which the speaker device according to the present invention is
applied to a projection type video projector. In this video projector, a plurality of sets of
ultrasonic wave generators 102 in which a plurality of piezoelectric elements 50 are combined
are disposed in a projector body 101. At this time, the respective ultrasonic wave generators 102
disposed in the projector main body 101 are directed to the screen surface 103 which is a
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25
projection surface of the video projector and other wall surfaces. When an ultrasonic wave is
emitted from each ultrasonic wave generator 102 toward the screen surface 103 or the wall
surface, the sound image of the audible sound can be localized at a place where the ultrasonic
wave emitted from the ultrasonic wave generator 102 is reflected.
[0106]
Therefore, ultrasonic waves corresponding to the audio signals for the right channel, left channel,
center channel, surround right channel and surround left channel of the multi-channel sound
source are emitted from each ultrasonic wave generator 102 By doing this, the viewer 104 can
be provided with reproduction sound of a multi-channel sound source.
[0107]
Furthermore, next, FIG. 20 shows an example in which the speaker apparatus according to the
present invention is applied to a video and audio apparatus using a thin video display apparatus
110 such as a liquid crystal display apparatus or a plasma display.
The speaker apparatus which comprises this audio-video apparatus attaches the ultrasonic wave
generator 114 which combined the several piezoelectric element 50 to the illumination reflective
plate 113 of the illuminating device 112 which is equipped with the illuminating tool 11 and is
suspended from a ceiling. The respective piezoelectric elements 50 constituting the ultrasonic
wave generator 114 are attached to the illumination reflection plate 113 with a predetermined
direction. At this time, the piezoelectric elements 50 constituting the ultrasonic wave generator
114 are combined to form, for example, a plurality of sets, and a filter is provided in front of the
piezoelectric elements 50 constituting each set. By making the frequency characteristic and the
phase characteristic different, the directivity of each set of piezoelectric elements 50 can be
directed to a direction other than the front.
[0108]
As described above, by changing the directivity direction of the ultrasonic wave emitted from
each piezoelectric element 50, the ultrasonic wave generator 114 combining the plurality of
piezoelectric elements 50 can be used for the right and left channels of the multichannel sound
source. By emitting ultrasonic waves corresponding to audio signals for the center channel, the
right channel for surround, and the left channel for surround, it is possible to provide the viewer
115 with reproduction sound of a multi-channel sound source.
08-05-2019
26
[0109]
And FIG. 21 shows the example which applied the speaker apparatus based on this invention to
the index apparatus 121 of an overhead projector.
The index device 121 emits a laser beam 122 and indexes a predetermined position of the
display surface 123 by the laser beam 122. A plurality of piezoelectric elements 50 are combined
on the emission surface side of the laser beam of the index device 121. The ultrasonic wave
generator 124 is disposed. In this manner, by incorporating the ultrasonic wave generator 124
into the index device 121, the explainer 125 emits an ultrasonic wave to the position 122a
indicated by the laser beam 122 and reflects it at the index position, whereby a sound image is
displayed at the index position 122a. Localization can be performed, sound can be combined
with an index of laser light, and effective information can be provided.
[0110]
Next, FIG. 22 shows an application of the speaker device according to the present invention to a
player 131 for reproducing an information recording medium in which information of multiple
languages is recorded. The regenerator 131 has an ultrasonic wave generator 134 in which a
plurality of piezoelectric elements 50 are combined along the upper edge of an apparatus body
133 including an image receiving unit 132. The ultrasonic wave generator 134 includes a
plurality of piezoelectric elements 50 as two ultrasonic wave generator groups 134a and 134b,
and the ultrasonic wave generator groups 134a and 134b are modulated by, for example, audio
signals corresponding to different languages. Was it? Driving by the modulation signal allows the
plurality of viewers 135 to independently listen to the voice of the desired language.
[0111]
Further, FIG. 23 shows an application of the speaker device according to the present invention to
a two-screen television receiver 141. The television receiver 141 has an ultrasonic wave
generator 144 in which a plurality of piezoelectric elements 50 are combined along the upper
edge of the receiver body 142. The plurality of piezoelectric elements 50 constituting the
ultrasonic wave generator 144 are combined as two ultrasonic wave generator groups 144a and
144b corresponding to the respective image receiving screens 141a and 141b. And are each
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27
modulated by the audio signal corresponding to each image receiving screen 141a, 141b from
each ultrasonic wave generator group 144a, 144b? By driving with the modulation signal, it is
possible to provide the audio corresponding to the video displayed on each of the image
reception screens 141a and 141b to the respective viewers 145 without affecting each other.
[0112]
Furthermore, FIG. 24 shows an application of the speaker device according to the present
invention to a television receiver 151. The television receiver 151 has an ultrasonic wave
generator 154 in which a plurality of piezoelectric elements 50 are combined along the upper
edge of the receiver main body 152. Here, the directivity of each piezoelectric element 50 of the
ultrasonic wave generator 154 is directed to the left and right ears of the listener 155
respectively, and is the frequency modulation of the binaurally recorded audio signal as
described above? By driving each piezoelectric element 50 by the modulation signal, it becomes
possible to listen to stereophonic sound without using headphones.
[0113]
Also in the speaker apparatus applied to the player 131 or the television receiver 141 shown in
FIG. 22 and FIG. 23 described above, similarly, the directivity of each piezoelectric element 50 is
directed to the left and right ears of the listener, respectively. By driving each of the piezoelectric
elements 50 with the modulation signal obtained by frequency-modulating the audio signal
recorded in the above as described above, it becomes possible to listen to three-dimensional
sound without using a headphone.
[0114]
25 shows an application of the speaker device according to the present invention to an exhibition
room of a museum or museum, and an ultrasonic wave generator 162 in which a plurality of
piezoelectric elements 50 are combined with a ceiling at a position where an exhibit 161 is
displayed. Is placed.
At this time, by directing the directivity of the ultrasonic wave generator 162 to the front of the
exhibit, only the viewer 163 who appreciates the exhibit 161 can listen to the reproduced sound,
and makes other places quiet and exhibits The acoustic environment of the room can be
improved.
08-05-2019
28
[0115]
Next, the speaker device shown in FIG. 26 emits ultrasonic waves from an ultrasonic wave
generator 171 combining a plurality of piezoelectric elements 50 toward the diaphragms 172
and 173 disposed at separated positions, and these diaphragms 172 , 173 in order to obtain
reproduced sound in the audible range. The diaphragms 172 and 173 are formed by stretching a
film or the like on the frame bodies 172a and 173a with a predetermined tension.
[0116]
With this configuration, it is not necessary to provide a power source or a drive unit on the
diaphragm 172, 173 side, and the selection of the installation place can be expanded.
[0117]
By designing the diaphragms 172 and 173, the diaphragms 172 and 173 can be used as indoor
fixtures and the like.
[0118]
Furthermore, FIG. 27 applies the speaker apparatus according to the present invention to a
television receiver 181, tracks the viewer 182, and changes the directivity by matching the
position of the viewer 182.
In the television receiver 181, an ultrasonic wave generator 184 in which a plurality of
piezoelectric elements 50 are combined is arranged along the upper edge of the receiver body
183, and a viewer 182 is further arranged along the upper edge of the ultrasonic wave generator
184. Position detection means 185 for detecting the position of
By changing the directivity of the ultrasonic wave generator 184 in accordance with the
detection output of the position detection means 185, ultrasonic waves are emitted in accordance
with the position of the viewer 182. At this time, the plurality of piezoelectric elements 50 are
arranged in two rows along the upper edge of the receiver main body 183.
08-05-2019
29
[0119]
Furthermore, FIG. 28 shows another example in which the speaker apparatus according to the
present invention is applied to a television receiver 191, which has means for rotating or moving,
and recognizes a specific one by image processing. An imaging and tracking mechanism 192
adapted to follow the specific one is installed on the upper surface of the receiver main body
193, and an ultrasonic wave generator 194 combining a plurality of piezoelectric elements 50 is
attached to a part of the imaging and tracking mechanism 192. It is
[0120]
The plurality of piezoelectric elements 50 constituting the ultrasonic wave generator 194 are
arranged on both sides of the imaging and tracking mechanism 192 one by one.
[0121]
It is possible to provide audio information only to the viewer 195 by attaching the ultrasonic
wave generator 194 so as to rotate or move integrally with the imaging and tracking mechanism
192 adapted to follow a specific one in this manner. Become.
[0122]
The loudspeaker apparatus according to the present invention frequency-modulates the audio
signal output from the sound source into a signal of a frequency band higher than at least the
audible band by the modulation means, and uses the frequency-modulated signal from the
modulation means for ultrasonic waves. Since the generating element is driven and the ultrasonic
wave from the ultrasonic generating element is reflected to the space or vibration plane to obtain
an audible sound, extremely high directivity can be obtained, and sound image localization can
be performed at any desired position. It can be set to
08-05-2019
30
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