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DESCRIPTION JP2006003405

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DESCRIPTION JP2006003405
PROBLEM TO BE SOLVED: To dispose an ultrasonic speaker in a cooling duct of a projector,
output an acoustic signal from an exhaust port of the cooling duct, and eliminate noise generated
from an exhaust port of the cooling duct. SOLUTION: An environmental sound around an exhaust
port 31 on the front of a main body of a projector 10 is collected by a microphone 33, a noise
signal is extracted from the collected environmental sound signal, and an erasing signal for
erasing the noise signal Generate Further, a carrier wave signal source 11 for generating a
carrier wave signal in an ultrasonic frequency band and an audio frequency band signal
oscillation source 12 for generating an audio frequency band signal are provided. Also, the
cancellation signal and the audio frequency band signal output from the audio frequency band
signal oscillation source 12 are synthesized to generate a synthesized acoustic signal. Then, the
carrier wave signal is modulated by this synthesized acoustic signal, the ultrasonic speaker 15 is
driven by this modulated signal, and the synthesized acoustic signal is converted into an
ultrasonic wave and output. [Selected figure] Figure 2
Projector and mute control method in projector
[0001]
The present invention relates to a projector that outputs an acoustic signal using an ultrasonic
speaker, and a mute control method in the projector, and in particular, the ultrasonic speaker is
disposed in a cooling duct, and the sound radiated from the ultrasonic speaker is The present
invention relates to a projector capable of outputting from an exhaust port and eliminating (or
reducing) noise generated around an exhaust port of a cooling duct, and a mute control method
in the projector.
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[0002]
Conventionally, it is known that an ultrasonic speaker that utilizes the non-linearity of the
medium (air) for ultrasonic waves can reproduce signals in the audio frequency band with a
much sharper directivity than that of a normal speaker.
[0003]
As a configuration, a carrier signal in the ultrasonic frequency band is modulated by a signal
from a signal source in the audio frequency band, amplified by a power amplifier or the like,
converted to a sound wave of finite amplitude level from an ultrasonic transducer, and ), And
reproduce the signal sound of the original audio frequency band by the non-linear effect of the
medium (air).
In this case, the reproduction range of the reproduction signal in the audio frequency band is a
beam-like range in the direction of the emission axis from the ultrasonic transducer (see, for
example, Patent Document 1).
[0004]
By the way, the noise level of the noise generated in the cooling duct by the cooling fan of the
electronic device, especially the liquid crystal projector etc. and the cooling fan is about 40 dB,
and has been improved to 30 several dB as the home application spreads recently. 30 dB or less
is desirable for home theater applications.
However, with the increase in brightness, large-sized, high-power cooling fans are used to cool
the lamps, liquid crystal panels, power supplies, and optical elements, and the noise from the
cooling fan and cooling ducts becomes even greater. It has become.
[0005]
In addition, some inventions are already disclosed as a prior art about the noise removal
technology which generate | occur | produces from an electronic device. For example, the
invention is disclosed for the purpose of providing an acoustic device that can easily remove
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2
noise emitted from a noise source such as a built-in CR-ROM. The present invention relates to a
microphone unit disposed in the vicinity of a noise generation source, and a non-linear circuit for
removing signal components other than noise components from the output of the microphone
unit, in an acoustic device including a speaker for sound reproduction and a noise generation
source. An applied filter that generates a signal in antiphase with noise based on an output of the
non-linear circuit; a speaker unit that converts an output signal of the applied filter into an
acoustic signal; a microphone unit disposed in the vicinity of the speaker unit; And a control unit
that controls the filter parameter of the applied filter so that the same signal component as the
output signal of the non-linear circuit among the signal components of the output of the
microphone unit is minimized (for example, see Patent Document 2).
[0006]
However, although the noise in the duct can be reduced by the prior art invention, the noise
generated at the time of output depending on the duct output shape can not be dealt with. JP-A58-119293 JP-A-2000-39887
[0007]
The present invention has been made to solve such a problem, and an object of the present
invention is to arrange an ultrasonic speaker inside a cooling duct of a projector and to utilize the
self-demodulation characteristic of the ultrasonic speaker to achieve a cooling duct. It is an object
of the present invention to provide a projector and a mute control method in the projector that
can eliminate (or reduce) the noise generated from the output section (exhaust port) of the
projector.
[0008]
The present invention has been made to solve the above problems, and a projector according to
the present invention is provided with an exhaust port of a cooling duct at the front of the
projector, and an ultrasonic speaker is disposed in the cooling duct. A projector for outputting an
acoustic output of a speaker from an exhaust port of the cooling duct, the microphone provided
in the vicinity of the exhaust port on the front of the main body for collecting environmental
sound around the exhaust port, and an environment collected by the microphone A cancellation
signal generator for extracting a noise signal from a sound signal and generating an cancellation
signal for erasing the noise signal component, a carrier wave signal source for generating a
carrier wave signal in an ultrasonic frequency band, and an audio frequency band An audio
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frequency band signal oscillation source for generating a signal, an erasing signal generated by
the cancellation signal generation unit, and an audio signal output from the audio frequency
band signal oscillation source A signal synthesis processing unit that synthesizes a signal of a
wave number band and generates a synthetic acoustic signal; and a modulation signal which is
driven by a modulation signal obtained by modulating the carrier wave signal with the synthetic
acoustic signal; And a sound wave transducer.
According to such a configuration, the exhaust port of the cooling duct is provided on the front of
the projector, and the ultrasonic speaker is disposed in the cooling duct, and the acoustic output
of the ultrasonic speaker is output from the exhaust port of the cooling duct. Also, a microphone
is installed at the exhaust port of the cooling duct to collect environmental sound around the
exhaust port. Then, the erasing signal generation unit extracts a noise signal from the
environmental sound, and generates an erasing signal for erasing the noise signal component
based on the noise signal. Further, the signal synthesis processing unit synthesizes the
cancellation signal generated by the cancellation signal generation unit and the signal of the
audio frequency band output from the audio frequency band signal oscillation source to generate
a synthesized acoustic signal. Then, the carrier wave in the ultrasonic frequency band output
from the carrier wave signal source is modulated by the synthetic acoustic signal, and the
modulation signal is converted into a sound wave by the ultrasonic transducer and output.
Accordingly, a microphone is installed at the exhaust port of the cooling duct of the projector to
collect environmental sound, and an erasing signal for erasing noise (exhaust sound) generated
from the exhaust port is added to the reproduction sound signal of the ultrasonic speaker.
Exhaust noise cancellation can be realized. In addition, although it is difficult to completely
eliminate exhaust noise (noise) in practice, continuous exhaust noise etc. can be eliminated (or
reduced), and an exhaust port utilizing the feature of specific location reproduction with an
ultrasonic speaker Can provide a noise cancellation method. As a secondary effect, the radiation
direction of the self-demodulated sound of the ultrasonic speaker is the same as that of the
cooling air, and the sound emission from the windward is enhanced, so the propagation
efficiency of the acoustic output of the ultrasonic speaker is improved.
[0009]
In the projector according to the present invention, the exhaust port of the cooling duct is
provided on the front of the projector, and the ultrasonic speaker is disposed in the cooling duct,
and the acoustic output of the ultrasonic speaker is output from the exhaust port of the cooling
duct A projector, provided in the vicinity of an exhaust port on the front of the main body, for
collecting environmental sound around the exhaust port, a carrier wave signal source for
generating a carrier wave signal in an ultrasonic frequency band, and a signal in an audible
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frequency band An audio frequency band signal generating source generating an audio
frequency band, an audio frequency band signal buffer storing an audio frequency band signal
output from the audio frequency band signal generating source for a preset time, and sound
collected by the microphone Component of the audio frequency band signal stored in the audio
frequency band signal buffer from the ambient sound signal, and Noise signal, and an erasing
signal generation unit that generates an erasing signal for erasing the noise signal, an erasing
signal generated by the erasing signal generating unit, and the audio frequency band signal
oscillation source. A signal synthesis processing unit that synthesizes an audio frequency band
signal and generates a synthesized acoustic signal; and a modulation signal generated by
modulating the carrier wave signal with the synthesized acoustic signal; And a sound wave
transducer. With such a configuration, the audio frequency band signal buffer (sound signal such
as audio signal) output from the audio frequency band signal oscillation source is saved by the
audio frequency band signal buffer for a preset time. Then, the component of the audio
frequency band signal (acoustic signal such as audio signal) stored in the audio frequency band
signal buffer is removed from the environmental sound signal in the vicinity of the exhaust port
collected by the microphone, and pure at the exhaust port of the cooling duct An environmental
sound signal (noise signal) is acquired, and based on this noise signal, an erasure signal is
generated to eliminate noise at the exhaust port. And this cancellation | release signal and the
signal of the audio frequency band output from an audio frequency band signal oscillation source
are synthesize | combined, a synthetic | combination acoustic signal is produced | generated, and
it outputs from an ultrasonic transducer. Thus, a microphone is installed near the exhaust port of
the cooling duct of the projector to collect environmental sound, and an audible frequency band
signal can be removed from the environmental sound signal to extract a noise signal. Then, an
erasing signal for erasing noise (exhaust sound) is generated from the noise signal, and the
erasing signal can be added to the reproduction sound signal of the ultrasonic speaker to realize
exhaust noise cancellation. In addition, although it is difficult to completely eliminate exhaust
noise, it is possible to eliminate (or reduce) continuous exhaust noise etc., and to eliminate noise
at the exhaust port utilizing the feature of specific location reproduction with an ultrasonic
speaker We can provide a way.
As a secondary effect, the radiation direction of the self-demodulated sound of the ultrasonic
speaker is the same as that of the cooling air, and the sound emission from the windward is the
sound radiation, so the propagation efficiency of the acoustic output of the ultrasonic speaker is
improved.
[0010]
Further, in the projector according to the present invention, the cancellation signal generation
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unit performs FFT processing on the noise signal extracted from the environmental sound signal
to decompose the noise signal into frequency components, and the FFT It is characterized by
including a phase / amplitude adjustment unit that generates a cancellation signal by performing
phase adjustment and amplitude adjustment of desired frequency components based on the
frequency analysis result by the processing unit. With such a configuration, an FFT (Fast Fourier
Transform) processing unit performs FFT processing on the noise signal to decompose it into
frequency components. Then, the phase / amplitude adjustment unit performs phase adjustment
(for example, phase inversion) and amplitude adjustment on the components to be erased among
the components of the noise signal and adds them together to generate an erasure signal. As a
result, it is possible to effectively eliminate (or reduce) the noise signal generated regularly
(periodically) of the environmental sound signal (noise signal). For example, wind noise of a
cooling fan, motor noise, wind noise generated from a louver provided at an exhaust port can be
effectively eliminated (or reduced).
[0011]
In the projector according to the present invention, the cooling duct has a plurality of exhaust
ports, and the microphone, the ultrasonic transducer, the cancellation signal generation unit, and
the signal synthesis processing unit are provided according to each exhaust port. It is
characterized by providing. With such a configuration, when there are a plurality of exhaust
ports of the cooling duct, the noise of the exhaust port is eliminated corresponding to each
exhaust port. For this purpose, a microphone, an ultrasonic transducer, a cancellation signal
generation unit, and a signal synthesis processing unit are provided corresponding to each
exhaust port. As a result, even when the projector has a stereo reproduction function and
acoustic signals are output from a plurality of exhaust ports, noise at each exhaust port can be
eliminated (or reduced).
[0012]
Further, according to the noise reduction control method of the present invention, the exhaust
port of the cooling duct is provided on the front of the projector, and the ultrasonic speaker is
disposed in the cooling duct, and the acoustic output of the ultrasonic speaker is output from the
exhaust port of the cooling duct A sound reduction control method for a projector, comprising: a
microphone provided near an exhaust port on the front of the main body, and an environmental
sound collection procedure for collecting environmental sound around the exhaust port by the
microphone, and an environment collected by the microphone An erasing signal generating
procedure for extracting a noise signal from a sound signal and generating an erasing signal for
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erasing the noise signal component, and a carrier wave signal generating procedure for
generating a carrier wave signal of an ultrasonic frequency band by a carrier wave signal source
An audio frequency band signal generating procedure for generating an audio frequency band
signal by an audio frequency band signal oscillation source; Signal synthesis processing
procedure for synthesizing a cancellation signal generated by the control unit and a signal of an
audio frequency band output from the audio frequency band signal oscillation source to generate
a synthesized sound signal; and combining the carrier wave signal with the synthesized sound
signal And an acoustic signal output procedure of converting the modulated signal into a sound
wave and outputting the sound wave. According to such a procedure, the exhaust port of the
cooling duct is provided on the front of the projector, the ultrasonic speaker is disposed in the
cooling duct, and the acoustic output of the ultrasonic speaker is output from the exhaust port of
the cooling duct. Also, a microphone is installed at the exhaust port of the cooling duct to collect
environmental sound around the exhaust port. Then, according to the cancellation signal
generation procedure, a noise signal is extracted from the environmental sound, and based on
the noise signal, an cancellation signal for deleting the noise signal component is generated.
Further, according to the signal synthesis processing procedure, the cancellation signal generated
by the cancellation signal generation unit and the signal of the audio frequency band outputted
from the audio frequency band signal oscillation source are synthesized to generate a
synthesized acoustic signal. Then, the carrier wave in the ultrasonic frequency band output from
the carrier wave signal source is modulated by the synthetic acoustic signal, and the modulation
signal is converted into a sound wave by the ultrasonic transducer and output. Accordingly, a
microphone is installed at the exhaust port of the cooling duct of the projector to collect
environmental sound, and an erasing signal for erasing noise (exhaust sound) generated from the
exhaust port is added to the reproduction sound signal of the ultrasonic speaker. Exhaust noise
cancellation can be realized. In addition, although it is difficult to completely eliminate exhaust
noise, it is possible to eliminate (or reduce) continuous exhaust noise etc., and to eliminate noise
at the exhaust port utilizing the feature of specific location reproduction with an ultrasonic
speaker We can provide a way.
As a secondary effect, the radiation direction of the self-demodulated sound of the ultrasonic
speaker is the same as that of the cooling air, and the sound emission from the windward is
enhanced, so the propagation efficiency of the acoustic output of the ultrasonic speaker is
improved.
[0013]
Further, according to the noise reduction control method of the present invention, the exhaust
port of the cooling duct is provided on the front of the projector, and the ultrasonic speaker is
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disposed in the cooling duct, and the acoustic output of the ultrasonic speaker is output from the
exhaust port of the cooling duct A sound reduction control method for a projector, which
comprises a microphone in the vicinity of an exhaust port on the front of the main body and an
environmental sound collection procedure for collecting environmental sound around the
exhaust port by the microphone, and a carrier wave signal of an ultrasonic frequency band. A
carrier wave signal generating procedure generated by a carrier wave signal source, an audio
frequency band signal generating procedure generating an audio frequency band signal by an
audio frequency band signal oscillation source, and the audio frequency band signal for a
predetermined time An audio frequency band signal buffer procedure for storing an audio
frequency band signal output from an oscillation source in an audio frequency band signal
buffer; A component of the audio frequency band signal stored in the audio frequency band
signal buffer is removed from the environmental sound signal collected by the microphone, a
noise signal at the position of the microphone is acquired, and an erasing signal for erasing the
noise signal A signal combining process of combining an erasure signal generation procedure to
be generated, an erasure signal generated by the erasure signal generation procedure, and an
audio frequency band signal output from the audio frequency band signal oscillation source to
generate a synthesized acoustic signal A procedure and an acoustic signal output procedure of
driving an ultrasonic transducer by a modulation signal obtained by modulating the carrier wave
signal with the synthetic acoustic signal, converting the modulation signal into a sound wave and
outputting the sound wave. According to such a procedure, the audio frequency band signal
(sound signal such as audio signal) output from the audio frequency band signal oscillation
source is stored by the audio frequency band signal buffer for a preset time. Then, the
component of the audio frequency band signal (acoustic signal such as audio signal) stored in the
audio frequency band signal buffer is removed from the environmental sound signal in the
vicinity of the exhaust port collected by the microphone, and pure at the exhaust port of the
cooling duct An environmental sound signal (noise signal) is acquired, and based on this noise
signal, an erasure signal is generated to eliminate noise at the exhaust port. And this cancellation
| release signal and the signal of the audio frequency band output from an audio frequency band
signal oscillation source are synthesize | combined, a synthetic | combination acoustic signal is
produced | generated, and it outputs from an ultrasonic transducer. Thus, a microphone is
installed near the exhaust port of the cooling duct of the projector to collect environmental
sound, and an audible frequency band signal can be removed from the environmental sound
signal to extract a noise signal. Then, an erasing signal for erasing noise (exhaust sound) is
generated from the noise signal, and the erasing signal can be added to the reproduction sound
signal of the ultrasonic speaker to realize exhaust noise cancellation.
In addition, although it is difficult to completely eliminate exhaust noise, it is possible to
eliminate (or reduce) continuous exhaust noise etc., and to eliminate noise at the exhaust port
utilizing the feature of specific location reproduction with an ultrasonic speaker We can provide
a way. As a secondary effect, the radiation direction of the self-demodulated sound of the
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ultrasonic speaker is the same as that of the cooling air, and the sound emission from the
windward is the sound radiation, so the propagation efficiency of the acoustic output of the
ultrasonic speaker is improved.
[0014]
Further, in the noise cancellation control method of the present invention, in the cancellation
signal generation procedure, FFT processing is performed on the noise signal extracted from the
environmental sound signal, and the noise signal is decomposed into frequency components; It is
characterized in that it includes a phase / amplitude adjustment procedure which generates a
cancellation signal by performing phase adjustment and amplitude adjustment of desired
frequency components based on the frequency analysis result by the FFT processing procedure.
According to such a procedure, FFT processing is performed on the noise signal by FFT (Fast
Fourier Transform) processing to decompose each frequency component. Then, according to the
phase / amplitude adjustment procedure, phase adjustment (for example, phase inversion) and
amplitude adjustment are performed on the components to be erased among the components of
the noise signal, and they are added together to generate an erasure signal. As a result, it is
possible to effectively eliminate (or reduce) the noise signal generated regularly (periodically) of
the environmental sound signal (noise signal). For example, wind noise of a cooling fan, motor
noise, wind noise generated from a louver provided at an exhaust port can be effectively
eliminated (or reduced).
[0015]
Further, in the noise reduction control method of the present invention, there are a plurality of
exhaust ports of the cooling duct, and according to each exhaust port, an environmental sound
collection procedure by the microphone, the cancellation signal generation procedure, and the
signal synthesis processing procedure And an acoustic signal output procedure by the ultrasonic
transducer. According to such a procedure, when there are a plurality of exhaust ports of the
cooling duct, noises of the exhaust ports are eliminated corresponding to the respective exhaust
ports. For this purpose, environmental sound collection procedures by microphones, cancellation
signal generation procedures, signal synthesis procedures, and acoustic signal output procedures
by ultrasonic transducers are performed corresponding to each exhaust port. As a result, even
when the projector has a stereo reproduction function and acoustic signals are output from a
plurality of exhaust ports, noise at each exhaust port can be eliminated (or reduced).
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[0016]
Next, the best mode for carrying out the present invention will be described with reference to the
drawings.
[0017]
A feature of the projector and the mute control method in the projector according to the present
invention is that an ultrasonic speaker is disposed in a cooling duct of the projector to utilize a
cooling duct area such as a light valve.
Thereby, noise elimination such as exhaust noise and directivity improvement of the ultrasonic
speaker are realized.
[0018]
FIG. 1 is a view for explaining the basic configuration of a projector according to the present
invention. As shown in FIG. 1, in the projector 10 according to the present invention, an exhaust
port 31 of a cooling duct 30 is provided on the front of the projector 10 The ultrasonic speaker
15 is disposed closer to the exhaust port 31 of the cooling duct 30 with respect to the fan 32,
and the area of the cooling duct 30 for cooling the light valve and the power supply device is
utilized for the acoustic signal output of the ultrasonic speaker 15. Further, a straight duct shape
is formed from the front surface of the ultrasonic speaker 15 to the exhaust port 31 of the
cooling duct 30.
[0019]
Further, the microphone 33 is installed in the vicinity of the exhaust port 31 of the cooling duct
30 to collect the sound, and a signal for erasing the exhaust sound is added to the reproduction
sound signal on the ultrasonic speaker 15 side to realize the exhaust sound cancellation. In the
ultrasonic speaker 15, the self-demodulation is reproduced at a certain distance from the output
unit, so it is optimal for exhaust noise cancellation.
[0020]
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In addition, since the microphone 33 for sound collection naturally picks up reproduction sound,
it becomes a feedback control type muffling control system with exhaust sound from which an
original sound signal is removed.
[0021]
Further, the cooling duct 30 can be used like a waveguide (the output sound wave travels
through the cooling duct 30 as a waveguide), and the directivity of the ultrasonic speaker can be
improved.
In addition, since the radiation direction of the self-demodulated sound is the same as the cooling
air, and the sound is emitted from the windward, the propagation efficiency of the acoustic signal
is also improved.
[0022]
FIG. 2 is a block diagram showing an example of the configuration of the projector shown in FIG.
1, and shows parts directly related to the present invention.
[0023]
In the projector 10 shown in FIG. 2, the carrier wave signal source 11 generates a carrier wave
signal (for example, a 40 kHz sine (Sin) wave or the like) in the ultrasonic frequency band.
The audio frequency band signal generator 12 generates an audio frequency band signal (for
example, an audio signal). The modulation unit 13 modulates the carrier wave signal output from
the carrier wave signal source 11 with the synthetic acoustic signal received from the signal
synthesis processing unit 19 to generate a modulation signal. The power amplifier 14 amplifies
the modulation signal received from the modulation unit 13.
[0024]
The ultrasonic transducer (ultrasonic speaker) 15 converts the modulation signal by the
synthetic acoustic signal amplified by the power amplifier 14 into a sound wave (ultrasound) of a
finite amplitude level and emits it into the medium (in the air).
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[0025]
The audio frequency band signal buffer 16 stores an audio frequency band signal (for example,
an audio signal) output from the audio frequency band signal oscillation source 12 for a preset
time.
The audio frequency band signal stored in the audio frequency band signal buffer 16 is used for
signal separation processing in the cancellation signal generation unit 18. The signal storage
time in the audio frequency band signal buffer 16 is calculated by calculating the propagation
time of the sound wave from the distance between the ultrasonic transducer (ultrasonic speaker)
15 and the exhaust port 31 of the cooling duct. It becomes the time which considered processing
time.
[0026]
The signal synthesis processing unit 19 synthesizes the cancellation signal output from the
cancellation signal generation unit 18 and the signal of the audio frequency band output from
the audio frequency band signal oscillation source 12 to generate a synthesized acoustic signal.
Also, the generated synthetic sound signal is passed to the modulation unit 13.
[0027]
The microphone sound collection unit 17 receives the microphone sound collection signal
(environmental sound signal) from the microphone 33 and passes the microphone sound
collection signal to the cancellation signal generation unit 18.
[0028]
FIG. 3 is a diagram showing a configuration example of the cancellation signal generation unit
18, and the noise signal extraction unit 181 in the cancellation signal generation unit 18
generates the microphone sound collection signal (environment sound signal) received from the
microphone sound collection unit 17. Then, the component (scale consideration) of the audio
frequency band signal stored in the audio frequency band signal buffer 16 is removed, and a
noise signal at the position of the microphone 33 of the exhaust port 31 is obtained.
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[0029]
Further, the FFT processing unit 182 extracts periodic signal components by frequency analysis
of the noise signal extracted by the noise signal extraction unit 181.
The phase adjustment unit 183 performs phase adjustment (for example, phase inversion of 180
degrees, etc.) on the frequency component to be erased among the frequency components of the
noise signal.
Further, the amplitude adjustment unit 184 adjusts the amplitude of the phase-adjusted signal to
generate a signal for noise cancellation. In addition, the amplitude adjustment unit 184
superposes the frequency components of the phase-amplitude-adjusted noise signal to generate a
cancellation signal.
[0030]
As mentioned above, although the structural example of the projector by this invention was
demonstrated by FIG. 1 and FIG. 2, as an electronic device to which this invention is applied, not
only a projector but an ultrasonic speaker (ultrasonic transducer) and a cooling duct are used.
Any electronic device may be used. For example, the present invention is also applicable to an
audio device, a TV receiver, a DVD device, and the like.
[0031]
Further, FIG. 4 is a diagram showing a flow of processing of an acoustic signal output by an
ultrasonic speaker (ultrasonic transducer), and a flowchart of a basic processing procedure for
outputting an acoustic signal by the ultrasonic speaker (ultrasonic transducer) 15 FIG.
[0032]
Referring to FIG. 4, first, audio frequency band signal generation (sound signal generation) is
performed by audio frequency band signal oscillation source 12 (step S1).
Further, the carrier wave signal source 11 generates a carrier wave signal in the ultrasonic
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13
frequency band (step S2).
For example, a 40 kHz sine (Sin) wave is generated.
[0033]
Next, the carrier wave signal of the ultrasonic frequency is AM-modulated by the audio frequency
band signal by the modulation unit 13 (step S3), and the modulation signal is amplified by the
power amplifier 14 (step S4). Then, the modulation signal is converted into a sound wave
(ultrasound) by the ultrasonic transducer 15 and emitted into the air (step S5). A parametric
effect occurs during air propagation of the emitted sound wave (ultrasound), and the audio
frequency sound is self-demodulated (step S6).
[0034]
Further, FIG. 5 is a diagram showing a flow of processing procedures of environmental sound
collection and noise elimination by the microphone, in which environmental sound around the
exhaust port of the cooling duct is collected by the microphone and noise elimination
accompanying it. It is the figure which showed the processing procedure with the flowchart.
Hereinafter, the processing procedure will be described with reference to FIG.
[0035]
First, environmental sound in the outside (near the exhaust port) of the cooling duct 30 is
recorded by the microphone 33 and the microphone sound collecting unit 17, and an
environmental sound signal is generated (step S11).
[0036]
Next, the cancellation signal generation unit 18 removes an acoustic signal (a signal generated by
the audio frequency band signal oscillation source 12) from the environmental sound signal, and
finally generates an cancellation signal (step S12).
[0037]
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14
In this case, with regard to the acoustic signal (the signal generated by the audio frequency band
signal oscillation source 12) included in the environmental sound obtained through the
microphone sound collecting unit 17, the time and each process involved in the propagation of
the acoustic signal in the air It is necessary to handle in consideration of the processing time in
the department.
For that purpose, as described above, the audio frequency band signal buffer 16 is provided, and
the acoustic signal (audio frequency band signal output from the audio frequency band signal
oscillation source 12) is stored for a preset time, thereby It is possible to refer back to the sound
signal.
In addition, as the signal storage time in the audio frequency band signal buffer 16, for example,
the propagation time of the sound wave is calculated from the distance between the ultrasonic
speaker 15 and the exhaust port 31 of the cooling duct. Can be considered time.
[0038]
Then, using the acoustic signal (signal of the audible frequency band) stored in the audible
frequency band signal buffer 16, the acoustic signal (signal generated by the audible frequency
band signal oscillation source 12) is removed from the environmental sound signal, Obtain a
pure environmental sound signal (noise signal) at the exhaust. Then, the phase adjustment unit
183 and the amplitude adjustment unit 184 (see FIG. 3) perform phase adjustment (for example,
180 degree phase inversion) and amplitude adjustment of the noise signal to generate a signal
for erasing.
[0039]
In this case, an FFT (Fast Fourier Transform) process is performed on a pure environmental
sound signal (noise signal) by the FFT processing unit 182 (see FIG. 3), and the phase of each
component is decomposed after being decomposed for each frequency component. The inverted
signals are added together to generate an erase signal. For example, for the phase adjustment
unit 183 (see FIG. 3), one whose circuit characteristic inverts each frequency component is used.
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[0040]
Next, the signal synthesis processing unit 19 synthesizes the cancellation signal generated by the
cancellation signal generation unit 18 and an audio frequency band signal (such as an audio
signal) output from the audio frequency band signal oscillation source 12 to generate
synthesized sound. A signal is generated (step S13). Further, the carrier wave signal is AMmodulated by the synthetic acoustic signal by the modulator 13 (step S14).
[0041]
Thereafter, the processing of step S4, step S5, step S6 (FIG. 4), and step S11, step S12, step S13,
step S14 (FIG. 5) is repeated. The processing need not always be performed, and may be
performed at intervals. In that case, a mechanism for buffering the generated erase signal is
provided.
[0042]
FIG. 6 is a view for explaining another basic configuration of the projector of the present
invention, for stereo sound reproduction using two combinations of an exhaust port of a cooling
duct and an ultrasonic speaker (ultrasonic transducer). Shows an example of the projector 10a.
[0043]
The projector 10a shown in FIG. 6 newly comprises a portion for outputting an L (left side)
acoustic signal as compared with the projector 10 shown in FIG. 1, a cooling duct 30a, a cooling
fan 32a, and an ultrasonic speaker 15a is provided, and a microphone 33a is provided at the
exhaust port 31a.
The cooling duct 30, the cooling fan 32, the ultrasonic speaker 15, and the microphone 33
constitute a portion that outputs an R (left side) acoustic signal. Further, the operation of each
part is the same as the operation described in FIG. 1, and the description thereof will be omitted.
[0044]
FIG. 7 is a block diagram showing an example of the configuration of the projector shown in FIG.
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16
6, and shows parts directly related to the present invention.
[0045]
In the projector 10 a shown in FIG. 7, the modulation unit 13, the power amplifier 14, the
ultrasonic speaker (ultrasound transducer) 15, the audio frequency band signal buffer 16, the
microphone sound collection unit 17, the cancellation signal generation unit 18, and the signal
combination processing unit 19. , The cooling duct 30, and the microphone 33 constitute a
portion that outputs an R (right side) acoustic signal.
[0046]
The modulation unit 13a, the power amplifier 14a, the ultrasonic speaker (ultrasound
transducer) 15a, the audio frequency band signal buffer 16a, the microphone sound collection
unit 17a, the cancellation signal generation unit 18a, the signal synthesis processing unit 19a,
the cooling duct 30a, and The microphone 33a constitutes a portion that outputs an L (left side)
acoustic signal.
[0047]
The operation of each part is basically the same as that described with reference to FIG. 2, but
audio frequency band signals on the L side and R side are generated from the audio frequency
band signal oscillation source 12, and the ultrasonic speaker 15 The difference is that the sound
signal on the R (right) side is output, and the sound signal on the L (left) side is output from the
ultrasonic speaker 15a.
[0048]
Further, in the example shown in FIG. 7, the carrier wave signal source 11 and the audio
frequency band signal oscillation source 12 are shared for generating the L side and R side
acoustic signals, but each of the L side and the R side May be provided separately.
Further, in the example shown in FIG. 7, the combination of the cooling duct and the ultrasonic
speaker (ultrasonic transducer) shows two examples, but of course, the combination of the
cooling duct and the ultrasonic speaker is three or more. It does not matter.
[0049]
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17
Further, in the configuration example of the projector shown in FIGS. 2 and 7, the carrier wave
signal generated by the carrier wave signal source 11 is shared for noise cancellation and for an
acoustic signal (audio frequency band signal such as an audio signal). Although an example is
shown, the frequency of the carrier wave signal may be used for noise cancellation and acoustic
signal (audio frequency band signal such as audio signal).
For example, the frequency of the carrier wave signal for noise cancellation may be 80 kHz, and
the frequency for the acoustic signal may be 40 kHz.
[0050]
The embodiment of the present invention has been described above, but the projector according
to the present invention is not limited to the illustrated example described above, and it goes
without saying that various modifications can be made without departing from the scope of the
present invention. It is.
[0051]
In the present invention, when the ultrasonic speaker is disposed in the cooling duct and the
sound of the ultrasonic speaker is output from the exhaust port of the cooling duct, an effect of
eliminating noise generated around the exhaust port of the cooling duct is exhibited. Thus, the
present invention is useful for a projector, a mute control method for the projector, and the like.
[0052]
The figure for demonstrating the basic composition of the projector of this invention.
FIG. 2 is a block diagram showing a configuration example of a projector shown in FIG. 1.
FIG. 7 is a diagram showing an example of the configuration of an erasure signal generation unit.
The figure which shows the flow of a process of the acoustic signal output by an ultrasonic
speaker.
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18
The figure which shows the flow of the processing procedure of environmental sound collection
and noise cancellation. The figure for demonstrating the other basic composition of the projector
of this invention. FIG. 7 is a block diagram showing a configuration example of a projector shown
in FIG. 6.
Explanation of sign
[0053]
DESCRIPTION OF SYMBOLS 10, 10a ... Projector, 11 ... Carrier wave signal source, 12 ... Audio
frequency band signal oscillation source, 13, 13a ... Modulating part 14, 14a ... Power amplifier,
15, 15a ... Ultrasonic transducer (Ultrasonic speaker) 16, 16a ... Audio frequency band signal
buffer 17, 17a ... Microphone sound collection unit 18, 18a ... Erasing signal generation unit, 181
... Noise signal extraction unit, 182 ... FFT processing unit 183 ... Phase adjustment unit, 184 ...
Amplitude adjustment unit, 19, 19a: Signal synthesis processing unit 30, 30a: Cooling duct, 31,
31a: Exhaust port, 32, 32a: Cooling fan 33, 33a: Microphone
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19
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