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DESCRIPTION JP2015201671

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DESCRIPTION JP2015201671
An object of the present invention is to output a vibration that can be felt by a listener while
realizing level reduction of signal output and power saving when transmitting an acoustic signal
output from a sound source to the listener as vibration. According to one embodiment, an
oscillatory sound device detects an absolute value of an amplitude of an acoustic signal output
from a sound source and then performs an integration process to output an acoustic signal and
an envelope detection unit that detects an envelope signal. And a low-frequency output speaker
provided on the vibration-transmitting member, the vibration-transmitting member being capable
of causing the listener to feel the vibration of low-frequency sound output from the lowfrequency output speaker. And a frequency conversion means for generating an acoustic signal
subjected to frequency conversion processing based on the resonance frequency by multiplying
the envelope signal by a sine wave having the same frequency as the resonance frequency
obtained by the impulse response. The acoustic signal subjected to frequency conversion
processing in the frequency conversion means is output from the low frequency output speaker.
[Selected figure] Figure 3
Vibration sound device, vibration sound output method and vibration sound program
[0001]
The present invention relates to a vibro-acoustic apparatus, a vibro-acoustic output method, and
a vibro-acoustic program, and more specifically, a vibro-acoustic apparatus capable of causing a
listener to feel as a vibration an output sound output from a sound source. It relates to a
vibration sound program.
[0002]
11-04-2019
1
Many seat audio systems have been proposed in which speakers are installed on the seat of a
vehicle for the purpose of enhancing the acoustic effect in the vehicle interior.
(For example, refer to Patent Document 1 and Patent Document 2). A typical seat audio system is
installed near the headrest of the seat, and a full-range speaker capable of reproducing a wide
range of sound from low to high, and installed in the middle or bottom of the seat It is comprised
by the subwoofer which can reproduce area sound intensively.
[0003]
By embedding the subwoofer inside the seat, the seat vibrates according to the low-level signal
level of the music, and the vibration is transmitted to the listener. It is possible to give listeners
high sense of reality. In addition, as the subwoofer embedded in the inside of the sheet, for
example, a dynamic speaker using cone paper or the like, an exciter that outputs a sound by
vibrating the contact surface, and the like are often used.
[0004]
In addition, by outputting various warning sounds from the sound source, not only auditory
warning can be performed simply as sound (warning sound), but also bodily sensational warning
by vibration can be performed, so that a warning such as a warning to listeners can be
recognized. It is possible to improve the degree.
[0005]
JP 2007-65038 A JP 2008-72165 A
[0006]
However, in a sheet audio system in which the listener feels the sound output and the vibration
by embedding the subwoofer inside the sheet, the output sound output from the subwoofer is
greatly reduced in the process of being output from the inside of the sheet to the surface, In
addition, vibrational components also tended to decrease greatly.
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2
For this reason, in order to have a listener sitting on a seat experience sufficient vibration, a large
level of acoustic output is required in the subwoofer.
In order to realize a large level of acoustic output, a power amplifier with a large amplification
factor and a large output is required, resulting in an increase in power consumption and cost.
[0007]
In particular, when a warning is given by vibration, a larger vibration tends to be required to
ensure that the seat occupant of the seat notices the warning, and the above-mentioned problems
of increase in power consumption and cost increase are more noticeable. It was a thing.
[0008]
Also, even when the subwoofer is installed on a member capable of transmitting vibrations other
than the seat, the output of the output sound is greatly reduced in the process until the listener is
made to feel the vibration. Had a problem of
[0009]
The present invention has been made in view of the above problems, and in the case where an
acoustic signal output from a sound source is transmitted to a listener as a vibration, the listener
can reduce the level of the signal output and save power. It is an object of the present invention
to provide a vibro-acoustic apparatus, a vibro-acoustic output method, and a vibro-acoustic
program capable of outputting a sensible vibration.
[0010]
In order to solve the above problems, the vibration acoustic apparatus according to the present
invention comprises an envelope detection unit that detects an envelope signal by performing
integration processing after obtaining an absolute value of the amplitude of an acoustic signal
output from a sound source. And a low-frequency output speaker for outputting the acoustic
signal, the vibration transmission member being capable of causing the listener to feel the
vibration of low-frequency sound outputted from the low-frequency output speaker, and the
vibration transmission An acoustic wave on which a frequency conversion process based on a
resonance frequency is performed by multiplying the envelope signal by a sine wave having the
same frequency as the resonance frequency obtained by the impulse response of the lowfrequency output speaker provided in a member And a frequency conversion means for
generating a signal, wherein the acoustic signal subjected to the frequency conversion processing
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3
in the frequency conversion means is output from the low-frequency output speaker And
butterflies.
[0011]
Further, in the vibration / acoustic output method according to the present invention, an
envelope detection step detects an envelope signal by performing integration processing after
obtaining an absolute value of the amplitude of the sound signal output from the sound source.
And the envelope signal having the same frequency as the resonance frequency determined by
the impulse response of the low frequency output speaker provided on the vibration
transmission member capable of causing the listener to experience the vibration of low
frequency sound, A frequency conversion step of generating an acoustic signal subjected to
frequency conversion processing based on a resonance frequency by multiplying the frequency
conversion step by the frequency conversion step; and the low frequency output speaker is a row
of the frequency conversion processing in the frequency conversion step. And an acoustic signal
output step of outputting the acoustic signal.
[0012]
Furthermore, the vibration acoustic program for the vibration acoustic apparatus according to
the present invention outputs the low frequency sound from the low frequency output speaker
provided in the vibration transmission member, thereby allowing the listener to receive the low
frequency through the vibration transmission member. A vibration sound program for a vibration
sound apparatus for experiencing vibration of sound, wherein an integral processing is
performed after obtaining an absolute value of an amplitude of a sound signal output from a
sound source, whereby an envelope is detected in an envelope detection means. The envelope
signal is multiplied by an envelope detection function for detecting a signal, and a sine wave
having the same frequency as the resonance frequency determined by the impulse response of
the low-frequency output speaker, thereby multiplying the envelope signal by the frequency
conversion means. A frequency conversion function of generating an acoustic signal subjected to
frequency conversion processing based on the frequency conversion function, the frequency
conversion function in the frequency conversion function, and Characterized in that it is a
vibroacoustic program for vibration acoustic device for realizing an acoustic signal output
function to output the sound signal subjected to the processing.
[0013]
In the vibration acoustic apparatus, the vibration acoustic output method, and the vibration
acoustic program for the vibration acoustic apparatus according to the present invention, the low
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4
frequency sound output from the low frequency output speaker is the resonance frequency of
the low frequency output speaker provided in the vibration transmission member Since the
frequency conversion processing is performed based on the above, it becomes possible to
effectively increase the signal level of the low frequency range sound.
For this reason, the vibration transmitted to the listener via the vibration transmission member
can be increased by the frequency conversion process of the resonance frequency, so that the
low frequency output can be obtained when the listener feels the same vibration as the
conventional one. The signal level of the low frequency range sound to be output from the
speaker can be made smaller than before, and the amount of power of the amplifier etc. can be
significantly reduced.
[0014]
Furthermore, the low frequency sound output from the low frequency output speaker can be felt
as a vibration to the listener, and this vibration can be increased by frequency conversion
processing based on the resonance frequency.
For this reason, for example, in the case of giving a notification such as a warning, it is possible
to give the listener a sensation by physically feeling as vibration as well as hearing.
[0015]
Further, the above-described vibration acoustic apparatus changes the signal level of a sine wave
having the same frequency as the resonance frequency while outputting the sine wave from the
low frequency output speaker based on the low frequency sound collected. The signal component
of the resonance frequency is extracted from the signal components of the entire band in the low
frequency sound to obtain the distortion component, and the ratio of the signal component of the
resonance frequency to the distortion component is calculated according to the variable signal
level. By the distortion factor measuring means for measuring the distortion factor in the low
band output speaker, and the signal level of the low band sound outputted from the low band
output speaker is below the upper limit of the signal level reproducible by the low band output
speaker Dynamic range compression means for suppressing the signal level of the envelope
signal for each resonance frequency based on the distortion rate measured by the distortion rate
measurement means. It has the frequency conversion means may perform the frequency
conversion processing on the envelope signal the signal level is suppressed by the dynamic range
compression means.
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5
[0016]
Furthermore, the above-described vibration sound output method is based on the low frequency
sound collected by outputting the sine wave from the low frequency output speaker while
varying the signal level of the sine wave having the same frequency as the resonant frequency.
The distortion component is determined by extracting the signal component of the resonance
frequency from the signal components of all bands in the low frequency sound, and the ratio of
the signal component of the resonance frequency to the distortion component is calculated
according to the variable signal level. Thus, the distortion factor measurement step measures
distortion factor in the low frequency output speaker, and the low frequency signal output from
the low frequency output speaker can be reproduced by the low frequency output speaker.
Dynamic range compression means for generating the envelope signal of the envelope signal
based on the distortion factor measured in the distortion factor measurement step so as to fall
below the upper limit of the signal level. The frequency conversion means for the envelope signal
whose signal level has been suppressed in the dynamic range compression step in the frequency
conversion step. The frequency conversion process may be performed.
[0017]
Further, the vibration sound program for the vibration sound apparatus described above is a low
sound collected by outputting the sine wave from the low frequency output speaker while
varying the signal level of the sine wave having the same frequency as the resonance frequency.
The signal level at which the ratio of the signal component of the resonance frequency to the
distortion component is varied by extracting the signal component of the resonance frequency
from the signal components of the entire band in the low band sound based on the range sound
The distortion factor measurement function causes the distortion factor measurement means to
measure the distortion factor in the low band output speaker, and the low band sound signal
output from the low band output speaker is the low band Based on the distortion factor
measured by the distortion factor measurement function, the dynamic range compression means
is configured to be equal to or less than the upper limit of the signal level reproducible by the
output speaker. A dynamic range compression function for suppressing the signal level of the
envelope signal for each of the resonance frequencies, and in the frequency conversion function,
the envelope signal whose signal level is suppressed by the dynamic range compression function;
The vibration sound program for a vibration sound apparatus may be characterized in that the
frequency conversion means performs the frequency conversion processing.
[0018]
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6
In the vibration acoustic apparatus, the vibration acoustic output method, and the vibration
acoustic program for the vibration acoustic apparatus according to the present invention, the
distortion factor in the low frequency output speaker is measured based on the signal component
of the resonance frequency, and output from the low frequency output speaker Based on the
distortion factor, the signal level of the envelope signal is suppressed for each resonant
frequency so that the signal level of the low-range sound is below the upper limit of the
reproducible signal level of the low-range output speaker, and then the frequency conversion
processing is performed. Do.
For this reason, it becomes possible to prevent the low range sound from being output beyond
the reproduction capability of the low range output speaker, distortion of the low range sound
output from the low range output speaker, It is possible to effectively prevent the burnout of the
range output speaker.
[0019]
Further, in the above-described vibration acoustic apparatus, vibration acoustic output method,
and vibration acoustic program for a vibration acoustic apparatus, the vibration transmission
member may be a chair on which the listener is seated.
[0020]
By using the chair on which the listener sits down as the vibration transmitting member, the
listener always contacts the vibration transmitting member for transmitting low-range sound as
vibration, so that the vibration can be reliably transmitted to the listener. It becomes possible.
Furthermore, a listener who sits on a chair can experience vibration on a wider surface by means
of a seat portion or a backrest portion, so that vibration can be felt more reliably.
[0021]
In the vibration acoustic apparatus, the vibration acoustic output method, and the vibration
acoustic program for the vibration acoustic apparatus according to the present invention, the low
frequency sound output from the low frequency output speaker is the resonance frequency of
the low frequency output speaker provided in the vibration transmission member Since the
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7
frequency conversion processing is performed based on the above, it becomes possible to
effectively increase the signal level of the low frequency range sound.
For this reason, the vibration transmitted to the listener via the vibration transmission member
can be increased by the frequency conversion process of the resonance frequency, so that the
low frequency output can be obtained when the listener feels the same vibration as the
conventional one. The signal level of the low frequency range sound to be output from the
speaker can be made smaller than before, and the amount of power of the amplifier etc. can be
significantly reduced.
[0022]
Furthermore, the low frequency sound output from the low frequency output speaker can be felt
as a vibration to the listener, and this vibration can be increased by frequency conversion
processing based on the resonance frequency.
For this reason, for example, in the case of giving a notification such as a warning, it is possible
to give the listener a sensation by physically feeling as vibration as well as hearing.
[0023]
FIG. 1 is a block diagram showing a schematic configuration of a seat audio system according to
an embodiment.
It is the figure which showed the state in which the 1st speaker which concerns on embodiment,
the 2nd speaker, and the subwoofer were installed in the sheet | seat.
It is the block diagram which showed schematic structure of the 2nd sound processing part
which concerns on embodiment.
(A) is the figure which showed the frequency characteristic of the low pass filter used as an
example in embodiment.
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8
(B) is a figure showing an example of a frequency characteristic of a low pass filter used in an
envelope detection part, when music is reproduced from a sound source part concerning an
embodiment as an acoustic signal. (A) shows the signal waveform of the downsampling signal
input to the envelope detection unit according to the embodiment, and (b) shows an absolute
value detection signal after the absolute value detection is performed in the envelope detection
unit And the signal waveform of the low pass filter output signal filtered by the low pass filter. It
is the figure which showed the frequency characteristic of the down sampling signal which
concerns on embodiment, an absolute value detection signal, and a low pass filter output signal.
It is the figure which showed the frequency characteristic of the impulse response calculated |
required by the subwoofer which concerns on embodiment. (A) shows the signal level change of
the acoustic signal inputted to the second power amplifier, (b) shows the same frequency
characteristic of the acoustic signal as (a), (c) shows the position near the surface of the sheet
FIG. 6 shows a signal level change of the signal sound collected by the microphone in FIG. 4, and
FIG. 4 (d) is a diagram showing frequency characteristics of the collected signal sound. (A) shows
the signal level change of the other acoustic signal inputted to the second power amplifier, (b)
shows the same frequency characteristic of the acoustic signal as (a), (c) shows the surface of the
sheet The signal level change of the signal sound collected with the microphone in the vicinity
position is shown, and (d) is the figure which showed the frequency characteristic of the signal
sound collected. In contrast to the configuration of the second acoustic processing unit shown in
FIG. 3, n dynamic range compression units corresponding to the number n of installed frequency
conversion units are provided between the envelope detection unit and the frequency conversion
unit. It is a block diagram showing a schematic configuration of another second sound processing
unit. It is the graph which showed an example of the measurement result of the signal
component of all the components which concern on embodiment, the signal component of a
primary component, the signal component of a distortion component, and a distortion factor. (A)
and (b) are diagrams showing the relationship between the amplitude state (upper diagram) of
the input acoustic signal and the first-order component and the distortion component with
respect to the signal components in the entire band, and (a) is The case where the signal level of
the input acoustic signal is small is shown, and (b) is the case where the signal level of the input
acoustic signal is large. It is the figure which showed the conversion characteristic of the signal
level suppressed by the 1st dynamic range compression part based on the look-up table set up by
the 1st level conversion part concerning an embodiment. When the signal level of the acoustic
signal output from the sound source unit according to the embodiment is large, signal level
changes when compression processing is performed by the dynamic range compression unit and
when it is not performed are converted to the second power amplifier. It is the figure shown
based on the value of the signal level of the acoustic signal input.
[0024]
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9
Hereinafter, the vibration sound apparatus according to the present invention will be described
in detail using a sheet audio system as an example thereof. FIG. 1 is a block diagram showing a
schematic configuration of a seat audio system.
[0025]
The seat audio system 100 includes a sound source unit (sound source) 110, a first sound
processing unit 120, a first power amplifier 130, a first speaker 140L, a second speaker 140R, a
second sound processing unit 200, and a second sound processing unit 200. A two-power
amplifier 150 and a subwoofer (low frequency output speaker) 160 are provided. Furthermore,
in the seat audio system 100, a microphone 310, an impulse response measurement unit 320,
and a distortion factor measurement unit (distortion factor measurement unit) 330 are provided.
[0026]
The sound source unit 110 can output sound signals for the L channel and the R channel to the
first sound processing unit 120 and the second sound processing unit 200. The sound signal
output from the sound source unit 110 is not limited to general music, and may be, for example,
a ringtone of a mobile phone or various warning sounds. For example, when the seat audio
system 100 is used as an on-vehicle audio system, an obstacle is detected by a warning sound
output interlocked with a warning display in the meter panel, a detection device for an obstacle
outside the vehicle, or the like. It is possible to use as a sound signal outputted from the sound
source unit 110 a detection alarm sound or the like which is activated in the case of Therefore,
the sound source unit 110 is not limited to a device having a function for reproducing an audio
signal such as a CD or a DVD, but the audio signal output (reproduced) by another device may be,
for example, an external input terminal It is sufficient if it has a function of acquiring via at least
and outputting to at least the second sound processing unit 200 or the like.
[0027]
The first sound processing unit 120 has a role of adjusting the volume of the sound signal
acquired from the sound source unit 110. For example, as the first sound processing unit 120, a
volume for adjusting the volume of the input sound signal, an equalizer for performing sound
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10
field correction or the like according to the preference of the listener, and the like are used. The
acoustic signal subjected to acoustic processing such as volume adjustment in the first acoustic
processing unit 120 is output to the first power amplifier 130.
[0028]
The first power amplifier 130 has a function of performing signal amplification of the acoustic
signal input from the first acoustic processing unit 120 and outputting the signal to the first
speaker 140L and the second speaker 140R. The first speaker 140L and the second speaker
140R are configured by full-range speakers capable of performing wide band signal output from
low to high frequencies.
[0029]
FIGS. 2A and 2B show an example of a state in which the first speaker 140L, the second speaker
140R, and the subwoofer 160 are installed on the seat (vibration transmission member, chair)
170. The seat 170 is intended to aurally provide music and the like to a seated listener, and to
sense vibration based on low-frequency components such as music, and includes a headrest 171
and a backrest. A vibration transmitting member 172 and a seat portion 173 are provided.
[0030]
As shown in FIGS. 2A and 2B, the first speaker 140L and the second speaker 140R are provided
with respect to the headrest portion 171 of the seat 170 so as to be located near the left and
right ears of the listener. By installing the first speaker 140L and the second speaker 140R at
this position, it is possible to listen to the acoustic signals for the L channel and the R channel
respectively from the left and right direction of the listener.
[0031]
The seat portion 173 is structured to support the seated listener from below, and a backrest
portion 172 is attached to the seat portion 173 so as to be able to be raised and lowered.
[0032]
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11
The backrest portion 172 is provided with a subwoofer 160 so that the listener seated on the
seat 170 can feel the vibration of the sound output.
For example, as shown in FIG. 2, by installing the subwoofer 160 around the waist position of the
listener, it becomes possible to transmit vibration from the waist to the back. In the present
embodiment, an exciter is used as an example of the subwoofer 160.
[0033]
The listener can adjust the inclination angle of the backrest 172 according to preference, and the
backrest 172 supports the back of the listener and a headrest 171 attached to the top of the
backrest 172. So, it has a structure to support the listener's head. For this reason, when the
listener is seated on the seat 170 and the acoustic output is made from the first speaker 140L,
the second speaker 140R and the subwoofer 160, the listener seated on the seat 170 is in the
vicinity of the left ear position. Not only does it listen to the L channel sound signal from the first
speaker 140L installed, it not only listens to the R channel sound signal from the second speaker
140R located near the right ear position, but also outputs the bass from the subwoofer 160 Thus,
it is possible to listen to the low-range acoustic signal as sound and to sense the acoustic signal
transmitted through the backrest 172 as vibration.
[0034]
The second acoustic processing unit 200 has a role of extracting only the low frequency
component from the acoustic signal input from the sound source unit 110 and performing
frequency conversion processing on the low frequency acoustic signal. The detailed configuration
of the second sound processing unit 200 and the processing content thereof will be described
below. The low frequency acoustic signal subjected to frequency conversion processing in the
second acoustic processing unit 200 is output to the second power amplifier 150.
[0035]
The second power amplifier 150 has a role of performing signal amplification of the acoustic
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12
signal input from the second acoustic processing unit 200. The acoustic signal amplified by the
second power amplifier 150 is output to the subwoofer 160.
[0036]
FIG. 3 is a block diagram showing a schematic configuration of the second sound processing unit
200. As shown in FIG. The second sound processing unit 200 includes a monaural unit 201, a
downsampling unit 202, a volume control unit 203, an envelope detection unit (envelope
detection unit) 204, and n frequency conversion units 205 (hereinafter, one unit). The eye
frequency converter 205, the first frequency converter 205-1, the second frequency converter
205, the second frequency converter 205-2, ..., the n-th frequency converter 205, It is referred to
as the nth frequency converter 205-n. Frequency conversion means), a synthesis unit 206, and
an upsampling unit 207.
[0037]
The monaural unit 201 has a role of combining the acoustic signal for the L channel input by the
sound source unit 110 and the acoustic signal for the R channel into monaural. The acoustic
signal (monaural acoustic signal) converted into monaural in the monaural unit 201 is output to
the down sampling unit 202.
[0038]
[Down-sampling processing] The down-sampling unit 202 applies a low-pass filter to reduce the
amount of calculation of signal processing in the volume adjustment unit 203, the envelope
detection unit 204, the frequency conversion unit 205, and the synthesis unit 206. , Has a role of
thinning the sampling frequency. By performing the thinning process in the downsampling unit
202 in this manner, it is possible to reduce the data amount of the acoustic signal used for signal
processing. Here, the cutoff frequency of the low pass filter in the downsampling unit 202 is set
based on the frequency band in the sound source of the acoustic signal output from the
subwoofer 160.
[0039]
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13
FIG. 4A is a diagram showing the frequency characteristics of the low pass filter used as an
example in the downsampling unit 202 according to the present embodiment. As shown in FIG.
4A, the downsampling unit 202 according to the present embodiment applies a 1,024-tap FIR
filter as the low-pass filter and sets the cutoff frequency to 150 Hz. After performing the filtering
process using the low-pass filter shown in FIG. 4A, the sampling frequency is reduced to 32 and
the sampling frequency is reduced to reduce the acoustic signal having the sampling frequency
of 44.1 kHz. After sampling, it becomes possible to downsample to 1.38 kHz.
[0040]
[Volume Adjustment Processing] The volume adjustment unit 203 has a role of adjusting the
volume of the down-sampled sound signal. By performing the volume control in the volume
control unit 203, it is possible to adjust the signal level of the low frequency signal output from
the subwoofer 160 to the level desired by the listener.
[0041]
[Envelope detection process] The envelope detection unit 204 performs an integration process
(filter process) using a low-pass filter after performing absolute value detection on the sound
signal subjected to volume adjustment by the volume adjustment unit 203. Plays a role in
detecting the envelope of the acoustic signal.
[0042]
FIG. 4B shows an example of the frequency characteristic of a filter used as a low-pass filter of
the envelope detection unit 204 when music is reproduced from the sound source unit 110 as an
acoustic signal.
In the low pass filter shown in FIG. 4B, the case where a 256-tap FIR filter is applied and the
cutoff frequency is set to 20 Hz is shown.
[0043]
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14
Further, in FIG. 5A, a signal of a signal input to the envelope detection unit 204 (a downsampling signal subjected to volume adjustment by the volume adjustment unit 203 after being
down-sampled by the down sampling unit 202) FIG. 5 (b) shows a signal (absolute value
detection signal) after detection of an absolute value in the envelope detection unit 204 and a
signal (low frequency) integrated (filtered) by a low pass filter. 7 shows a signal waveform of a
pass filter output signal). Furthermore, FIG. 6 shows the frequency characteristics of the down
sampling signal, the absolute value detection signal, and the low pass filter output signal.
[0044]
As shown in FIGS. 5 (a), (b) and FIG. 6, the downsampling signal input to the envelope detection
unit 204 is subjected to signal processing to detect an absolute value detection signal, and the
low pass filter output signal By generating the envelope signal, the envelope detector 204 can
detect the envelope signal. In the envelope signal (low-pass filter output signal) shown in FIG. 6,
it can be confirmed that an acoustic signal of 20 Hz or less is detected as a baseband signal.
[0045]
[Frequency Conversion Processing] The frequency conversion unit 205 has a role of performing
frequency conversion on an envelope signal to be a baseband signal based on a resonance
frequency. The resonance frequency used in the frequency converter 205 is determined based on
the frequency state (more specifically, the peak frequency) of the impulse response measured by
the impulse response measuring unit 320 shown in FIG.
[0046]
FIG. 7 shows an example of a frequency characteristic of an impulse response obtained by
measuring an acoustic signal (impulse signal) output from the subwoofer 160 with the
microphone 310 when an exciter is used as the subwoofer 160. . By using the microphone 310
to measure the impulse response of the acoustic signal output from the subwoofer 160, it is
possible to measure the acoustic characteristic of the reproduction system between the
subwoofer 160 and the surface of the backrest 172. . FIG. 7 shows one obtained by Fouriertransforming the measured impulse response as a frequency characteristic.
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[0047]
As apparent from FIG. 7, in the acoustic characteristics of the reproduction system, two peak
frequencies with large signal levels are detected as resonance frequencies. In the present
embodiment, 28 Hz, which is the first peak frequency, is taken as the first resonance frequency
(the resonance frequency where n = 1), and 56 Hz, which is the second peak frequency, is taken
as the second resonance frequency (n = 2). (Resonance frequency) to be detected.
[0048]
The first detected resonance frequency of 28 Hz is set as the resonance frequency in the first
frequency conversion unit 205-1, and the second resonance frequency of 56 Hz is the resonance
frequency in the second frequency conversion unit 205-2. It is set.
[0049]
Then, in the first frequency conversion unit 205-1, with respect to the baseband signal (envelope
signal) detected by the envelope detection unit 204, the 28 Hz sine wave (28 Hz same as the
resonance frequency) set as the resonance frequency The low frequency signal in which the
resonance frequency of 28 Hz is emphasized is generated by multiplying the sine wave
Further, in the second frequency conversion unit, a 56 Hz sine wave (sine wave consisting of the
same 56 Hz as the resonance frequency) set as the resonance frequency with respect to the
baseband signal (envelope signal) detected by the envelope detection unit 204 The low frequency
signal in which the resonant frequency of 56 Hz is emphasized is generated by multiplying
(multiplying).
[0050]
In the present embodiment, since two frequencies of 28 Hz and 56 Hz are extracted as resonance
frequencies as shown in FIG. 7, the first frequency converter 205-1 and the second frequency
converter 205 as the frequency converter 205. Although the case where two (n = 2) frequency
conversion parts of -2 are provided is shown as an example, when a plurality of (for example, n)
peaks serving as resonance frequencies are detected, n resonance frequencies are provided. ,
Frequency conversion is performed in each of n frequency conversion units 205-1 to 205-n from
1 to n.
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[0051]
[Composition processing] The combining unit 206 has a role of combining the baseband signals
frequency-converted by the n frequency conversion units 205 based on the respective resonance
frequencies.
The combining unit 206 combines the signals subjected to frequency conversion in the
respective frequency conversion units 205 (the respective frequency conversion units 205 from
the first frequency conversion unit 205-1 to the nth frequency conversion unit 205-n) to perform
synthesis. Do. By this combining process, it is possible to combine the signals subjected to the
frequency conversion into one so as to correspond to the respective resonant frequencies. The
?frequency conversion process? according to the present invention means a process including
two processes of frequency conversion in the frequency conversion unit 205 and combining
processing in the combining unit 206. The low-pass signal synthesized by the synthesis unit 206
is output to the up-sampling unit 207.
[0052]
[Up-sampling processing] The up-sampling unit 207 inserts a zero corresponding to the number
of up-samples into the signal input from the synthesis unit 206, and then uses the same low-pass
filter as the down-sampling unit to fold the signal. Remove the ingredients. For example, when
the number of up samples is 32, the sampling frequency is converted from 1.38 kHz to 44.1 kHz
and converted to the same sampling frequency as the acoustic signal output from the sound
source unit 110.
[0053]
FIG. 8 (a) shows the signal level change of the acoustic signal (acoustic signal up-sampled by the
up-sampling unit 207) input to the second power amplifier 150, and FIG. 8 (b) shows the same
acoustic signal. It shows frequency characteristics. 8C shows the signal level change of the signal
sound collected by the microphone 310 at a position near the surface of the sheet 170, and FIG.
8D shows the frequency characteristic of the collected signal sound. ing. 8A to 8D do not
undergo frequency conversion processing by the frequency conversion unit 205, and the lowpass signal is output as it is to the second power amplifier 150. A signal is shown, and a signal of
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?with control? indicates a signal when frequency conversion processing is performed by the
frequency conversion unit 205 using a resonance frequency of 28 Hz.
[0054]
As shown in FIGS. 8 (a) and 8 (b), the signal levels of the acoustic signal input to the second
power amplifier 150 are substantially the same signal level with and without control. However,
comparing the signal levels of the signal sounds (Fig. 8 (c) and (d)) collected near the surface of
the sheet 170 after being output from the subwoofer 160, no control is better than control. It can
be confirmed that the level is smaller than 20 dB. That is, when the vibration state of the surface
of the sheet 170 is compared, it can be determined that the vibration level of the signal subjected
to the frequency conversion processing using the resonance frequency is larger than 20 dB.
[0055]
Therefore, in order to make listeners who are seated on the seat 170 feel the same vibration state
as compared to the non-control state and the control-on state, 20 dB is obtained in the case of
the non-control state. The above also requires the signal output at a large signal level. From the
same point of view, when making the listener feel the same vibration state, with control, it is
possible to feel the vibration sufficiently by performing signal output with a smaller signal level
compared to the case without control. Therefore, it is possible to realize a reduction in the output
of the second power amplifier 150 and a significant power saving.
[0056]
9 (a) to 9 (d) show signal level changes (FIG. 9 (a)) and frequency characteristics (a) of the
acoustic signal input to the second power amplifier 150, as in FIGS. 8 (a) to 8 (d). FIG. 9B shows
the signal level change (FIG. 9C) and the frequency characteristic (FIG. 9D) of the signal sound
collected by the microphone 310. However, the signals with control shown in FIGS. 9A to 9D
differ from those in FIGS. 8A to 8D in that frequency conversion processing is performed using
not only 28 Hz but also the resonance frequency of 56 Hz. There is. 9A and 9B reduce the signal
levels of 28 Hz and 56 Hz by 6 dB as compared with FIGS. 8A and 8B. In this reduction
processing, if frequency conversion is performed using two resonance frequencies, then the
synthesis processing is performed by the synthesis unit 206, and the signal level increases
compared to the case where frequency conversion is performed with only one resonance
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frequency at the time of synthesis. In consideration of the problem.
[0057]
As shown in FIGS. 9C and 9D, when the vibration state in the vicinity of the surface of the sheet
170 is detected using an acoustic signal subjected to frequency conversion processing using two
resonance frequencies, the signal level without control is detected. The signal level of 17 dB or
more is detected higher in the signal level with control than in the case of FIG. For this reason,
even when frequency conversion is performed using a plurality of resonance frequencies, in
order to make the listener feel the same vibration state, signal output with a small signal level is
sufficient compared with control without control. The second power amplifier 150 can realize a
reduction in output power and a significant power saving.
[0058]
As described above, the resonance frequency of the subwoofer 160 is detected in advance, and
the frequency conversion processing of the sound signal output from the subwoofer 160 is
performed using the detected resonance frequency, thereby utilizing the resonance of the sound
signal at the resonance frequency. As a result, it is possible to make the listener experience the
increased low frequency vibration. For this reason, it is possible to realize the reduction of the
signal output and the significant power saving as compared with the case where the frequency
conversion processing based on the resonance frequency is not performed.
[0059]
On the other hand, when music or the like is used as the acoustic signal output from the sound
source unit 110, the frequency characteristic tends to change in various ways. For example, as
shown in FIG. 7, in the case of obtaining the frequency characteristic by the impulse response,
the frequency with a high signal level can be obtained as the resonance frequency. However,
when music or the like is output from the subwoofer 160, the frequency characteristics greatly
change, so signal levels of frequencies other than the resonance frequency are output as peaks,
dips occur, and the signal levels change. Do.
[0060]
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19
Therefore, when the frequency conversion processing based on the resonance frequency is not
performed, the vibration level output from the subwoofer 160 tends to largely change depending
on the characteristics of the music (music signal) output from the sound source unit 110. is
there. Therefore, the volume of the low range reproduced from the full range speakers (the first
speaker 140L and the second speaker 140R) provided in the headrest portion 171 does not
correspond to the amount of vibration in the low range output from the subwoofer 160. There is
a risk that the listener feels uncomfortable with the sound and the perceived vibration.
[0061]
In order to eliminate such a sense of discomfort between the sound to be heard and the
perceived vibration, frequency conversion processing is performed on the low-range sound signal
using the resonance frequency in the subwoofer 160 to control the vibration. By this, it becomes
possible to make the listener experience the vibration according to the vibration characteristic of
the signal without depending on the frequency characteristic change of the music signal
outputted from the sound source. For this reason, by controlling the low band signal by the
frequency conversion process using the resonance frequency, it becomes possible to make the
listener feel the vibration (vibration amount) corresponding to the volume reproduced from the
full range speaker.
[0062]
[Signal level suppression processing (dynamic range compression processing)] As described
above, by performing frequency conversion processing based on the resonance frequency, the
subwoofer 160 can reproduce a high level signal, If a signal with a level exceeding the playback
capacity of the subwoofer 160 is output from the subwoofer 160, the signal may be clipped and
distortion may occur, and the signal level becomes higher than the upper limit of the playback
capacity. There is also a risk of burning the voice coil. As described above, in order to prevent the
signal from being reproduced at a signal level exceeding the reproduction capability of the
subwoofer 160, the case where a process of compressing the dynamic range according to the
signal level is added to the second acoustic processing unit will be described. Do.
[0063]
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20
10 is the same as the configuration of the second acoustic processing unit 200 shown in FIG. 3
except for n units corresponding to the number n of installed frequency conversion units 205
between the envelope detection unit 204 and the frequency conversion unit 205. Dynamic range
compression unit (dynamic range compression means) 208 (hereinafter, the first dynamic range
compression unit 208 is a first dynamic range compression unit 208-1, the second dynamic
range compression unit 208 is a second dynamic range compression unit 208-2..., A block
diagram showing a schematic configuration of the second sound processing unit 200a in which
the nth dynamic range compression unit 208 is the nth dynamic range compression unit 208-n).
. The monaural unit 201, the downsampling unit 202, the volume adjustment unit 203, the
envelope detection unit 204, the frequency conversion unit 205, the synthesis unit 206, and the
upsampling unit 207 shown in FIG. The same reference numerals are given to the same
components as those already described above and also in FIG. 10, and the description here is
omitted.
[0064]
The acoustic signal output from the envelope detection unit 204 is input to each of the first
dynamic range compression unit 208-1 to the nth dynamic range compression unit 208-n. The
dynamic range compression unit 208 sets the level conversion unit corresponding to the level
conversion unit 209 (hereinafter, the n-th dynamic range compression unit 208-n) as the n-th
level conversion unit 209-n. And multipliers 210 (n multipliers 210 provided in the dynamic
range compressor 208 have the same configuration, and are provided one for each dynamic
range compressor 208, as shown in FIG. 10). There is. And.
[0065]
Each of the level conversion units 209-1 to 209-n uses a lookup table for the resonance
frequency of the frequency conversion units 205-1 to 205-n corresponding to each of the level
conversion units 209-1 to 209-n. Have a role in performing level conversion. The multiplication
unit 210 performs signal processing of the output acoustic signal (reduction / compression) by
multiplying the signal converted in level by the level conversion unit 209 by the acoustic signal
output from the envelope detection unit 204. Do. As such, by providing the level conversion unit
209 (209-1 to 209-n) and performing signal level adjustment (reduction and compression) on
the resonance frequency, an acoustic signal that exceeds the reproduction capability of the
subwoofer 160 Can be suppressed in advance, so that distortion of the output sound, burning of
the subwoofer 160, and the like can be prevented.
11-04-2019
21
[0066]
The look-up table of level converter 209 is determined based on the reproduction capability of
subwoofer 160 at each resonance frequency. The signal level serving as the upper limit of the
reproduction capability is output to the second power amplifier 150 while varying the signal
level of a sine wave having the same frequency as the resonance frequency using the distortion
factor measurement unit 330 shown in FIG. The low-frequency sound output from the subwoofer
160 via the second power amplifier 150 is determined based on the distortion factor measured
by detecting the distortion factor measurement unit 330 via the microphone 310.
[0067]
FIG. 11 is a graph showing an example of the measurement results of the distortion factor and
the like. FIG. 11 shows a measurement result when the signal level is changed from ?18 dB to 0
dB and output to the second power amplifier 150 using a 56 Hz sine wave which is one of the
resonance frequencies of the subwoofer 160. There is. The signal level on the horizontal axis of
FIG. 11 is in the range of ?18 dB to 0 dB because it is a value corresponding to the variable
range of the signal level. Also, in FIG. 11, based on the low band sound measured by the
distortion factor measurement unit 330 via the microphone 310, the signal levels of the signal
components in all bands (values of all components in FIG. 11) and the resonance frequency The
signal level (the value of the first-order component of FIG. 11) of a certain 56 Hz signal
component is shown, and after extracting the signal component (first-order component) of 56 Hz
from the signal components of all bands (all components) Signal components are shown as
distortion components. Further, FIG. 11 shows a distortion factor which is obtained by
subtracting the distortion component from the first order component (note that the subtraction
with the decibel value corresponds to division in linear).
[0068]
12 (a) and 12 (b) are diagrams showing the amplitude state (upper diagram) of the input acoustic
signal and the frequency characteristics (lower diagram) of the signal components of all bands
including the primary component and the distortion component. It is. More specifically, FIG. 12
(a) shows the amplitude state of the signal level (the upper diagram of (a)) and the frequency
characteristics of the signal components of the entire band ((a) when the signal level of the input
11-04-2019
22
acoustic signal is small. 12B shows the amplitude state of the signal level (the upper diagram of
(b)) and the frequency characteristics of the signal components in the entire band when the
signal level of the input acoustic signal is large. (The lower diagram of (b)) is shown.
[0069]
As shown in the lower part of FIGS. 12A and 12B, the distortion component is a signal
component in a frequency band higher than 56 Hz that indicates the peak of the primary
component, and is a signal component in a range where the signal level largely fluctuates Is the
case. That is, as shown in the lower part of FIGS. 12 (a) and 12 (b), components other than the
portion where the signal component (primary component) of 56 Hz is extracted from the signal
components (all components) in all bands are extracted as distortion components. Be done.
[0070]
For example, if the signal level at which the distortion factor is -10 dB is defined as the
reproduction capacity of the subwoofer 160, the signal level of the reproduction axis at the
horizontal axis when the distortion factor [dB] on the vertical axis shown in FIG. Is -11.5 dB. In
the first level conversion unit 209-1 that performs level conversion of a signal level with a
resonance frequency of 56 Hz, setting of the look-up table is performed so that the signal level of
-11.5 dB becomes the upper limit.
[0071]
FIG. 13 is a diagram showing the conversion characteristics of the signal level suppressed by the
first dynamic range compression unit 208-1 based on the look-up table set by the first level
conversion unit 209-1. As shown in FIG. 13, while the input signal is up to -13.5 dB, the signal
level of the input signal becomes the signal level of the output signal as it is, and the signal
suppression processing is not performed.
[0072]
However, when the input signal passes -13.5 dB, signal suppression processing is started, and
11-04-2019
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when the input signal reaches 0 dB (full scale), the signal level of the output signal is obtained
from the relationship of the distortion factor in FIG. The suppression is performed so as to be
?11.5 dB, which is the signal level of the reproduction ability to be reproduced. In this manner,
a look-up table is set based on the reproduction capability of the subwoofer 160 defined based
on the distortion factor, and signal level suppression processing (dynamic range compression
processing) in each dynamic range compression unit 208 is performed. By being performed, it
can be suppressed that the signal level of the low frequency sound outputted from the subwoofer
160 becomes larger than the upper limit of the reproduction capability of the subwoofer 160.
For this reason, it is possible to suppress the occurrence of distortion to the low frequency range
sound output from the subwoofer 160, and it is possible to prevent burnout.
[0073]
FIG. 14 is a case where the compression processing is performed by the dynamic range
compression unit 208 (when the suppression in FIG. 14 is performed) when the signal level
(volume) of the acoustic signal output from the sound source unit 110 is large. It is a figure
which showed the signal level change of (the suppression of FIG. 14) based on the value of the
signal level of the acoustic signal input into the 2nd power amplifier 150. FIG. Specifically, FIG.
14 shows the case where the signal level is increased by increasing the volume by 11 dB with
respect to the signal level with control shown in FIG.
[0074]
As shown in FIG. 14, since the signal level is not suppressed (limited) in the dynamic range
compression unit 208 when there is no suppression, the signal level of the acoustic signal input
to the second power amplifier 150 is the same as that of the subwoofer 160. The value is higher
than -11.5 dB, which is the upper limit of the reproduction capability. However, since the signal
level is suppressed (limited) by the dynamic range compression unit 208 in the case of
suppression, the signal level of the acoustic signal input to the second power amplifier 150 is the
upper limit of the reproduction capability of the subwoofer 160. Is suppressed within -11.5 dB.
For this reason, the low frequency sound output from the subwoofer 160 is also suppressed
within the range of the reproduction capability of the subwoofer 160 (below the upper limit),
distortion occurs in the output sound, and the subwoofer 160 burns out. Can be effectively
prevented.
[0075]
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24
As described above, by using the sheet audio system 100 according to the present embodiment,
the low-frequency sound output from the subwoofer 160 is subjected to frequency conversion
processing based on the resonance frequency of the subwoofer 160. It is possible to effectively
increase the vibration of the low range sound. For this reason, it is easy to realize the reduction in
the output of the second power amplifier 150 and the significant power saving.
[0076]
Furthermore, in the sheet audio system 100 according to the present embodiment, the change in
distortion factor is determined based on the signal component (primary component) for each
resonance frequency, and the subwoofer 160 set as the upper limit of the reproduction capability
of the subwoofer 160 It is also possible to set the look-up table of the level conversion unit 209
by determining the signal level that is the upper limit of the reproduction capability based on the
distortion factor of. By performing signal level suppression of the acoustic signal output from the
dynamic range compression unit 208 using the look-up table of the level conversion unit 209 set
in this manner, the output from the subwoofer 160 by frequency conversion based on the
resonance frequency It is possible to prevent the low frequency sound being output from being
output beyond the reproduction capability of the subwoofer 160. For this reason, it is possible to
effectively prevent distortion in the output sound (low-range sound) output from the subwoofer
160 or burnout in the subwoofer 160.
[0077]
Furthermore, by using the sheet audio system 100 according to the present embodiment, the
listener can feel the output sound as vibration, so for example, a warning sound linked to the
alarm system, an acoustic signal of the sound source unit 110 Not only can the warning be heard
aurally by the warning sound, but also it can be felt as vibration by inputting as. For this reason,
it is possible to more effectively notify the listener of the warning, and it becomes possible to
more effectively notify the listener of the acoustic signal as vibration.
[0078]
Further, in the seat audio system 100 according to the present embodiment, the subwoofer 160
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is installed on the backrest portion 172 of the seat 170. By providing the subwoofer 160 on the
seat 170, the listener's back seated on the seat 170 always contacts the backrest portion 172 of
the seat 170, and it becomes possible to reliably transmit the vibration to the listener.
Furthermore, the listener seated on the seat 170 can sense vibration on a wider surface
(vibration transmission surface) by the backrest 172 and the like, and thus can sense vibration
more reliably.
[0079]
As mentioned above, although the vibration audio apparatus concerning this invention was
demonstrated using the sheet | seat audio system 100 as an example, the vibration audio
apparatus concerning this invention is not limited to what was shown in embodiment.
[0080]
For example, in the seat audio system 100, the case where the subwoofer 160 is installed on the
backrest 172 of the seat 170 is used as an example.
However, the installation location of the subwoofer 160 is not limited to the backrest 172 of the
seat 170 as long as the listener can feel the low-pass sound as vibration. For example, the
subwoofer 160 can be installed in the seat portion 173 of the seat 170, the headrest portion
171, and the like. In addition, it is sufficient if the listener can feel the low-range sound as
vibration, so, for example, vibration transmission that contacts parts of the listener's body, such
as the steering wheel of the vehicle, the elbow rest, the floor mat, etc. As long as the subwoofer
160 can be installed on a possible object, the installation position, the installation object, and the
like are not particularly limited.
[0081]
Further, in the example shown in FIG. 13, as the input signal increases from -13.5 dB to 0 dB, the
signal level of the output signal is suppressed so that the listener does not feel discomfort in the
signal level change due to the suppression process of the output signal. Although the processing
is performed gently, the signal level of the suppression processing is not limited to this range.
Therefore, the signal level of the input signal that starts the suppression process is not limited to
?13.5 dB, and the suppression process may be started from the value of another signal level. By
setting the processing status of the suppression processing more appropriately, it is also possible
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to alleviate the discomfort of the vibration of the output sound due to the suppression
processing.
[0082]
100 ... sheet audio system (vibration and acoustic device) 110 ... sound source unit (sound
source) 120 ... first sound processing unit 130 ... first power amplifier 140L ... first speaker 140R
... second speaker 150 ... second power amplifier 160 ... subwoofer (Low-frequency output
speaker) 170: Seat (vibration transmission member, chair) 171: headrest portion 172: backrest
portion (vibration transmission member) 173: seat portion 200, 200a: second sound processing
portion 201: monaural portion 202: down sampling Unit 203 ... Volume adjustment unit 204 ...
Envelope detection unit (envelope detection unit) 205, 205-1, ..., 205-n ... Frequency conversion
unit (frequency conversion unit) 206 ... Combining unit 207 ... Up sampling unit 208 , 208-1, ...,
208-n ... dynamic range compression unit (dynamic Nji compression means) 209,209-1, иии, 209-n
... level converting unit 210 ... multiplying unit 310 ... microphone 320 ... impulse response
measurement unit 330 ... distortion measurement unit (distortion measuring unit)
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