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JP2008205804

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DESCRIPTION JP2008205804
To provide an acoustic system capable of reducing noise of frequencies from low to middle high
frequency with high accuracy and efficiency. SOLUTION: A sound system 1 according to the
present invention comprises a reference microphone noise correction means 13 for applying a
filter process to a sound to be silenced collected by a reference microphone 7 to flatten
frequency characteristics; There are noise correction means 14 and 15 for correction
microphones which performs a filter process on the sound collected by the correction
microphones 5L and 5R provided near the position to flatten the frequency characteristics.
Furthermore, the sound system 1 is in the vicinity of the user's ear position based on the sound
filtered by the reference microphone noise correction unit 13 and the sound filtered by the
correction microphone correction units 14 and 15. Acoustic correction means 11, 12 for
generating an acoustic signal for reducing noise, and speakers 4L, 4R for outputting the acoustic
signal are provided. [Selected figure] Figure 2
Sound system
[0001]
The present invention relates to an acoustic system capable of reducing noise from low to middle
high frequencies.
[0002]
Heretofore, active noise control (ANC) control technology is known as one of the technologies for
reducing ambient noise.
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This is a technology that cancels the noise by picking up the noise by the microphone and
outputting the sound of the opposite phase from the speaker.
[0003]
In order to reduce noise in a vehicle, various configurations have conventionally been proposed,
and a method of performing ANC control using a speaker installed at a vehicle door has been
proposed as an example (for example, Patent Literature 1). Unexamined-Japanese-Patent No. 11133981
[0004]
However, in the case of the speaker installed in the vehicle door, the muffling position,
specifically, the vicinity of the ear position of the user getting on the vehicle and the installation
position of the speaker are relatively distant, so the propagation loss is large and the speaker
output is large There was a problem that the output level was required.
[0005]
In addition, in the medium-high range sound with a short wavelength, there is a problem that the
change in acoustic characteristics is easily affected by people and the load, and the applicable
frequency is limited to the low range.
[0006]
Furthermore, when the door is opened or closed when the vehicle is stopped, etc., the distance
from the user's ear position to the speaker changes, so the propagation distance of the sound to
the muffling position changes and the acoustic characteristics largely change. There is a problem
that the effect is reduced.
[0007]
In addition, since the magnitude and characteristics of the noise entering the vehicle
compartment change according to the traveling speed of the vehicle when the vehicle is
traveling, the processing delay increases with the increase in the processing load only with the
silencing control by active noise control. There was a possibility that etc. might occur.
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[0008]
The present invention has been made in view of the above problems, and an object of the present
invention is to provide an acoustic system capable of reducing noise of frequencies from low to
middle high frequency with high accuracy and efficiency.
[0009]
In order to solve the above problems, the audio system according to the present invention
comprises a reference microphone for picking up a sound to be silenced, a correction
microphone provided near the user's ear position, and a reference collected by the reference
microphone. Noise correction means for the reference microphone which filters the sound signal
of the microphone sound to flatten the frequency characteristic of the reference microphone
sound, and the sound signal of the correction microphone sound picked up by the correction
microphone is subjected to the filter processing Correction microphone noise correction means
for flattening the frequency characteristics of the correction microphone sound; an acoustic
signal of a reference microphone sound that has been subjected to filter processing by the
reference microphone noise correction means; and a filter using the correction microphone
correction means An acoustic signal for reducing noise in the vicinity of the user's ear position
based on the processed acoustic signal of the corrected microphone sound. And acoustic
correction means for forming, characterized in that it comprises a speaker for outputting the
output sound of the acoustic signal generated by the acoustic correcting means in the vicinity of
the ear position the user.
[0010]
In the above acoustic system, after the frequency characteristic of the reference microphone
sound (for example, noise) is flattened by the reference microphone noise correction unit, the
sound correction unit performs the muffling process, so the reference microphone sound has a
low response time with a fixed response time. It becomes possible to muffle uniformly over the
entire band from the high band to the high band.
[0011]
Furthermore, since the sound correction means performs the muffling process of the reference
mike sound using the correction microphone sound whose frequency characteristic is flattened
by the correction microphone noise correction means, the sound correction means effectively
performs the muffling process. It is possible to totally mute the reference microphone sound over
the entire range from low to high.
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[0012]
In the sound system, the correction microphone includes an L microphone provided in the
vicinity of the left ear position of the user and an R microphone provided in the vicinity of the
right ear position of the user, and the noise correction means for the correction microphone L
microphone noise correction means for filtering the sound signal of the corrected microphone
sound picked up by the L microphone to flatten the frequency characteristic of the corrected
microphone sound; and sound picked up by the R microphone And noise correction means for
the R microphone which filters the acoustic signal of the correction microphone sound to flatten
the frequency characteristic of the correction microphone sound, and the sound correction
means is a filter according to the noise correction means for the reference microphone. Based on
the acoustic signal of the reference microphone sound subjected to the processing and the
acoustic signal of the corrected microphone sound that has been subjected to the filter
processing by the L microphone correction means L channel acoustic correction means for
generating an L channel acoustic signal for reducing noise near the left ear position of the user,
and an acoustic signal of a reference microphone sound that has been subjected to filter
processing by the reference microphone noise correction means And an R channel acoustic
signal for reducing noise in the vicinity of the right ear position of the user based on the acoustic
signal of the correction microphone sound filtered by the R microphone correction means and
for the R channel An L speaker for outputting an output sound of the L channel acoustic signal
near the left ear position of the user; and an output sound of the R channel acoustic signal to the
right of the user. It may be provided with an R speaker that outputs in the vicinity of the ear
position.
[0013]
In such an audio system, L microphones and R microphones are respectively installed near the
user's left and right ear positions in order to mute the reference microphone, and the corrected
microphone sound collected from each of L microphones and R microphones The (error sound) is
flattened using the L microphone noise correction means and the R microphone noise correction
means, and the reference microphone picked up by the reference microphone using the flattened
left and right correction microphone sounds. Since the sound (noise) is muffled separately on the
left and right using the L channel acoustic correction means and the R channel acoustic
correction means, the space is divided into left and right and independent muffling control is
performed in the vicinity of the user's left and right ears. be able to.
For this reason, even if there is a difference in noise at the left and right ear positions, it is
possible to reduce noise from the low range to the middle high range with high accuracy and
efficiency according to each noise.
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[0014]
Furthermore, in the sound system, the L microphone and the L speaker are disposed at the upper
left portion of a seat on which the user sits, and the R microphone and the R speaker are
disposed at the upper right portion of the sheet. May be
[0015]
As described above, the L microphone and L speaker are disposed at the upper left portion of the
seat, and the R microphone and R speaker are disposed at the upper right portion of the sheet,
whereby the positions of the user's ears seated on the seat Since the position and the position are
always kept constant, the user can enjoy a stable muffling effect.
[0016]
The sound system is installed in a vehicle, and the noise correction means for reference
microphone and the noise correction means for correction microphone are provided with a
plurality of types of correction filters for use in the filtering process, and are adapted to the
traveling speed of the vehicle The type of the correction filter used for the filter processing may
be changed.
[0017]
In such an acoustic system, by changing the type of correction filter used for the filtering process
according to the traveling speed of the vehicle, it is an optimum corresponding to the frequency
characteristics of the reference microphone sound and the correction microphone sound
different according to the traveling speed Since the correction filter can be selected, it is possible
to more appropriately and effectively flatten the frequency characteristics of the reference
microphone sound and the correction microphone sound.
[0018]
Furthermore, in the above-mentioned sound system, the speaker may be a full range speaker
capable of outputting an output sound from low to high frequencies.
[0019]
As described above, by using the full-range speaker capable of outputting the output sound from
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the low band to the high band as the speaker, it is not necessary to use a plurality of speakers
such as the low band speaker and the high band speaker.
As described above, since a single-speaker can output the mute signal of the entire band from the
low band to the high band, the system configuration can be simplified.
[0020]
According to the sound system of the present invention, the sound collected by the reference
microphone is subjected to the filter processing to flatten the frequency characteristic and then
the noise correction processing is performed by the sound correction means. It is possible to
obtain the muffling effect by the acoustic correction means in the entire band from the low band
to the middle high band.
[0021]
The acoustic system according to the present invention will be described in detail with reference
to the drawings.
[0022]
FIG. 1 is a view showing a schematic configuration of an acoustic system 1.
The sound system 1 is installed in the cabin of the vehicle, and as shown in FIG. 1, the muffling
speaker 4L (L speaker) installed on the left and right (left and right facing the front direction) of
the headrest portion 3 of the seat 2 of the vehicle. , A noise reduction speaker 4R (R speaker), an
error microphone 5L (L microphone, correction microphone) installed in the vicinity of the noise
reduction speakers 4L, 4R, an error microphone 5R (R microphone, correction microphone), and
a device main body performing noise control It has the part 6 and the reference microphone 7
which picks up the noise (noise, reference microphone sound) used as the noise reduction object.
Further, the device body 6 is connected to a vehicle speed sensor 9 for detecting the speed of the
vehicle, and it is possible to obtain vehicle speed information from the vehicle speed sensor 9.
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[0023]
A full range speaker capable of outputting sound from low to high frequencies is used for the
muffling speakers 4L and 4R, and the headrest is disposed in the vicinity of the left and right ear
positions of the user seated on the seat 2 It is provided in part 3.
The output surfaces of the muffling speakers 4L and 4R are disposed in a forward direction of
the seat 2 and are inclined inward at a predetermined angle toward the user's ear position
direction.
[0024]
As described above, by using the full-range speakers as the muffling speakers 4L and 4R, it is not
necessary to use a plurality of speakers such as the low band speaker and the high band speaker,
so that the system configuration can be simplified. .
[0025]
The error microphones 5L and 5R are also installed in the headrest portion 3 and are seated on
the seat 2 in order to obtain correction data (correction sound and correction microphone sound)
for mute processing near the user's left and right ear position. It is provided near the left and
right ear position of the user.
For this reason, the muffling speakers 4L and 4R and the error microphones 5L and 5R are
disposed at positions adjacent to each other.
[0026]
Note that the muffling speakers 4L and 4R and the error microphones 5L and 5R do not
necessarily have to be installed in the headrest portion 3 and may be disposed in the vicinity of
the left and right ear positions of the user. It may be one.
Thus, by arranging the error microphone 5L and the muffling speaker 4L in the upper left
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portion of the sheet 2 and arranging the error mike 5R and the muffling speaker 4R in the upper
right portion of the sheet 2, the user can effectively carry out the muffling effect. It can be
enjoyed.
[0027]
The reference microphone 7 is installed, for example, in an engine room, a trunk room, near a
front seat foot of a passenger compartment, near a mounting position of a tire, etc. in order to
pick up noise to be silenced.
For example, when the sound system according to the present embodiment is installed for the
purpose of silencing the driving noise of the engine, the reference microphone 7 is disposed in
the engine room, and the driving noise of the engine is collected by the reference microphone 7 .
Although only one reference microphone 7 is installed in this embodiment, a plurality of
reference microphones 7 may be provided depending on the noise target.
[0028]
As shown in FIG. 2, the device body 6 includes an L channel ANC unit (L channel acoustic
correction unit) 11, an R channel ANC unit (R channel acoustic correction unit) 12, and a
reference microphone noise correction. Unit (reference microphone noise correction unit) 13, L
microphone noise correction unit (L microphone noise correction unit) 14, R microphone noise
correction unit (R microphone noise correction unit) 15, L speaker correction And a correction
unit 17 for the R speaker.
[0029]
In addition, a vehicle speed sensor 9 provided in the vehicle is connected to the device body 6,
and the reference microphone noise correction unit 13, the L microphone noise correction unit
14, and the R microphone noise correction unit 15 are vehicle speed sensors. By receiving the
traveling speed information of the vehicle from 9, it is possible to determine the traveling speed
of the vehicle in real time.
[0030]
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The L-channel ANC unit 11 can cancel (silence) the sound (noise) collected by the reference
microphone 7 based on the sound signal (error signal) collected by the error microphone 5L.
Have a role to generate.
Noise can be silenced by creating a sound in reverse phase to the noise collected by the reference
microphone 7 by the L channel ANC unit 11 and superimposing it on the noise.
[0031]
Similarly, the R channel ANC unit 12 can cancel (silence) the sound (noise) collected by the
reference microphone 7 based on the sound signal collected by the error microphone 5R.
Generate
As an algorithm of the ANC process, known algorithms such as Filtered-x LMS (least mean
square) and Filtered-reference LMS can be used.
[0032]
The L channel ANC unit 11 receives an error signal whose frequency characteristic is corrected
to be flat in the L microphone noise correction unit 14 to be described later, and the R channel
ANC unit 12 is to be described later. In the noise correction unit 15, an error signal whose
frequency characteristic is corrected to be flat is input.
Further, a noise signal whose frequency characteristic is corrected to be flat in the reference
microphone noise correction unit 13 described later is input as noise to the L channel ANC unit
11 and the R channel ANC unit 12.
[0033]
FIG. 3 is a block diagram showing a schematic configuration of the L channel ANC unit 11.
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As shown in FIG. 3, the L channel ANC unit 11 includes a delay unit 20, an acoustic correction
unit 21, an LMS unit 22, an FIR filter unit 23, and a multiplication unit 24.
The configuration of the R channel ANC unit 12 is also the same as that of the L channel ANC
unit 11 shown in FIG.
[0034]
The delay unit 20 takes into consideration the delay time from the muffling speaker 4L (or the
muffling speaker 4R) to the error microphone 5L (or the error microphone 5R), the response
time of the muffling speaker 4L (or the muffling speaker 4R), etc. It is provided to perform delay
processing of the sound signal collected by 7.
[0035]
The sound correction unit 21 is provided to correct sound characteristics from the muffling
speaker 4L (or the muffling speaker 4R) to the error microphone 5L (or the error microphone
5R).
As shown in FIG. 4A, the output sound of the muffling speaker 4L provided on the left side of the
headrest portion 3 of the seat is an error provided on the right side as well as the error
microphone 5L provided on the left side of the user U It is also transmitted to the microphone
5R.
At this time, the sound pressure level of the output sound from the muffling speaker 4L to the
error microphones 5L and 5R changes according to the frequency while passing through the
space.
[0036]
For example, as shown in FIG. 4A, when sound is output from the muffling speaker 4L and the
muffling speaker 4R, the sound of the muffling speaker 4L is transmitted to the error
microphone 5L installed on the left side of the user U. Between the muffling speaker 4R and the
error microphone 5L when the sound characteristic between the muffling speaker 4L and the
error microphone 5L is transmitted to C11 and the sound of the muffling speaker 4R is
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transmitted to the error microphone 5L installed on the left side of the user U The acoustic
characteristics of C12, the acoustic characteristics between the muffling speaker 4L and the error
mike 5R when the sound of the muffling speaker 4L is transmitted to the error microphone 5R
installed on the right side of the user U are C21 and The acoustic characteristics between the
muffling speaker 4R and the error microphone 5R when the sound is transmitted to the error
microphone 5R installed on the right side of the user U are C22. To.
[0037]
In this case, the acoustic characteristics of the error microphone 5L and the error microphone 5R
in the muffling speaker 4L are shown as shown in FIG. 4 (b), and the acoustic characteristics of
the error microphone 5L and the error microphone 5R in the muffling speaker 4R are shown in
FIG. It is shown as).
[0038]
In the acoustic correction unit 21 of the L channel ANC unit 11, an acoustic signal (acoustic
signal of the reference microphone 7 subjected to delay processing by the delay unit 20) based
on the acoustic characteristic of the muffling speaker 4L shown in FIG. 4B. Sound correction
processing is performed, and sound correction processing is performed on the sound signal in
the sound correction unit 21 of the R-channel ANC unit 12 based on the sound characteristics of
the muffling speaker 4R illustrated in FIG. It will be.
[0039]
However, as apparent from FIG. 4B, the level of the acoustic characteristic C11 of the sound
transmitted from the muffling speaker 4L to the error microphone 5L installed on the left side of
the user U is the same as that of the user U from the muffling speaker 4L. Indicates a value
higher than the level of the acoustic characteristic C21 of the sound transmitted to the error
microphone 5R installed on the right side of.
This is because the sound output by the muffling speaker 4L is blocked by the head of the user U
and hardly transmitted to the error microphone 5R installed on the right side of the user U.
Therefore, in the acoustic correction unit 21 of the L channel ANC unit 11 shown in the present
embodiment, the acoustic signal (referring to the delay processing performed by the delay unit
20 is performed using only the acoustic characteristic C11 shown in FIG. An acoustic correction
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process is performed on the acoustic signal of the microphone 7).
[0040]
Further, as apparent from FIG. 4C, the level of the acoustic characteristic C22 of the sound
transmitted from the muffling speaker 4R to the error microphone 5R installed on the right side
of the user U corresponds to the user U from the muffling speaker 4R. Indicates a value higher
than the level of the acoustic characteristic C12 of the sound transmitted to the error
microphone 5L installed on the left side of the.
This is also because the sound output by the muffling speaker 4R is difficult to be transmitted to
the error microphone 5L installed on the left side of the user U because the user U's own head is
interrupted.
Therefore, also in the acoustic correction unit of the R channel ANC unit 12 shown in the present
embodiment, an acoustic signal (a reference microphone subjected to delay processing by the
delay unit using only the acoustic characteristic C22 shown in FIG. 4C) Sound correction
processing is performed on the sound signal 7).
[0041]
As described above, in the sound correction processing in the sound correction unit 21, since the
level of the sound characteristic (cross component) at which the muffling speaker and the error
microphone cross each other is low, the sound correction unit is set without considering the
cross component. Thus, it is possible to perform spatially independent left and right mute control
processing.
[0042]
The LMS unit 22 performs a least squares algorithm based on the acoustic signal collected by the
error microphone 5L (or the error microphone 5R) and the acoustic signal of the reference
microphone 7 acoustically corrected by the delay unit 20 and the acoustic correction unit 21.
The coefficient control of the FIR filter unit 23 is performed using this.
[0043]
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The FIR filter is a finite impulse response filter, and based on the FIR filter unit 23 subjected to
coefficient control by the LMS unit 22, processing of the acoustic signal collected by the
reference microphone 7 is performed.
The phase of the output signal processed by the FIR filter unit 23 is inverted by the
multiplication unit 24.
[0044]
The reference microphone noise correction unit 13 has a role of performing frequency correction
of noise signals to be muted such as traveling noise and engine sound of a vehicle collected by
the reference microphone 7.
5A shows a frequency characteristic example 30 of noise collected by the reference microphone
7, a frequency characteristic example 31 of a correction filter used for the filter processing of the
reference microphone noise correction unit 13, and a filter processing. And a frequency
characteristic example 32 of the noise.
5 (a) and 5 (b) show linear frequency characteristics for convenience of explanation, but in
reality, they are as shown in FIGS. 7 (b) and 8 (a) (b) described later. It shows frequency
characteristics of non-linear shape.
[0045]
As shown in FIG. 5A, the reference microphone noise correction unit 13 filters noise using a
correction filter that has an inverse characteristic of the frequency characteristic 30 of the noise.
It is possible to correct the noise collected by the reference microphone 7 to a flat (flat)
frequency characteristic 32 by filtering the noise using a correction filter having such an inverse
characteristic. Become.
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[0046]
The traveling noise and the engine sound collected by the reference microphone 7 are
characterized in that the characteristics of the noise change according to the traveling state of
the vehicle, more specifically, the traveling speed of the vehicle.
FIG. 6 (a) shows an example of frequency characteristics of noise when the speed of the vehicle is
0 km / h (so-called idling state), and FIG. 6 (b) shows an example of frequency characteristics of
noise when the speed of the vehicle is 50 km / h. FIG. 7A shows an example of the frequency
characteristic of noise when the speed of the vehicle is 100 km / h.
[0047]
As apparent from FIGS. 6 (a), 6 (b), and 7 (a), the level value [dB] of the noise is approximately
proportional to the speed of the vehicle and the level value in the corresponding frequency range
is high. Show a trend. For this reason, the reference microphone noise correction unit 13 records
a plurality of correction filters having frequency characteristics as schematically shown in FIG.
5B, and the speed information of the vehicle acquired from the vehicle speed sensor 9 is stored.
The correction filter is selected and determined based on the above, and the filtering process is
performed on the noise collected by the reference microphone 7 using the selected and
determined correction filter.
[0048]
As described above, by determining the correction filter used for the filtering process according
to the traveling speed of the vehicle, it is possible to more appropriately and effectively flatten
the frequency characteristic of the noise subjected to the filtering process. The acoustic signal
flattened by the reference microphone noise correction unit 13 is output as a noise signal to the
L channel ANC unit 11 and the R channel ANC unit 12.
[0049]
FIG. 7 (b) shows the noise picked up by the reference microphone 7 and the frequency
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characteristic example 35 before the correction processing (filter correction processing) is
performed by the reference microphone noise correction unit 13, and the noise for the reference
microphone FIG. 14 is a diagram showing a frequency characteristic example 36 after the
correction processing (filter correction processing) in the correction unit 13 has been performed.
As is clear from FIG. 7B, the noise shown in the frequency characteristic example 35 is subjected
to filter processing by the noise correction unit 13 for the reference microphone to maintain the
increase / decrease characteristics of the level value for each frequency. As shown in the
frequency characteristic example 36, it is possible to flatten the frequency characteristic example
35 of noise.
[0050]
The L microphone noise correction unit 14 filters the error sound (corrected microphone sound)
collected by the error microphone 5 L before (while not performing) the noise reduction
processing in the L channel ANC unit 11. It has a role to give. By applying a filtering process to
the error sound picked up by the error microphone 4L, it is possible to correct the frequency
characteristic of the error sound to a flat (flat) state.
[0051]
Similarly to the reference microphone noise correction unit 13, the L microphone noise
correction unit 14 records a plurality of correction filters according to the traveling speed of the
vehicle, and based on the vehicle speed information acquired from the vehicle speed sensor 9.
The correction filter is selected and determined, and the selected and determined correction filter
is used to filter the error sound picked up by the error microphone 5L.
[0052]
FIG. 8A is a diagram showing the frequency characteristic of the error sound picked up by the
error microphone 5L, and is an example of the frequency characteristic before the correction
processing (filter correction processing) is performed by the L microphone noise correction unit
14 37 and a frequency characteristic example 38 after correction processing (filter correction
processing) is performed in the L microphone noise correction unit 14 are shown.
As is clear from FIG. 8A, the error sound shown in the frequency characteristic example 37 is
subjected to the filtering process by the L microphone noise correction unit 14 to hold the
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15
increase / decrease state of the level value for each frequency. It is possible to flatten the
frequency characteristic example 37 of noise as shown in the frequency characteristic example
38 as it is.
[0053]
Also, the R microphone noise correction unit 15 similarly filters the error sound collected by the
error microphone 5R before (while not performing) the noise reduction processing in the R
channel ANC unit 12. Have a role. By applying a filter process to the error sound picked up by
the error microphone 5R, it is possible to correct the frequency characteristic of the error sound
to a flat (flat) state.
[0054]
Similarly to the reference microphone noise correction unit 13 and the L microphone noise
correction unit 14, the R microphone noise correction unit 15 also records a plurality of
correction filters according to the traveling speed of the vehicle, and acquires them from the
vehicle speed sensor 9. The correction filter is selected and determined based on the speed
information of the vehicle to be processed, and the filtering process is performed on the error
sound picked up by the error microphone R using the selected and determined correction filter.
[0055]
FIG. 8B is a diagram showing the frequency characteristic of the error sound picked up by the
error microphone 5R, which is the frequency characteristic before the correction processing
(filter correction processing) is performed by the noise correction unit 15 for R microphone. The
example 39 and the frequency characteristic example 40 after the correction processing (filter
correction processing) is performed in the R microphone noise correction unit 15 are shown.
As is clear from FIG. 8B, the error sound shown in the frequency characteristic example 39 is
subjected to the filtering process by the R microphone noise correction unit 15 to hold the
increase / decrease state of the level value for each frequency. It is possible to flatten the
frequency characteristic example 39 of noise as shown in the frequency characteristic example
40 as it is.
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[0056]
The L speaker correction unit 16 prevents the frequency characteristics of the mute signal from
changing according to the characteristics of the mute speaker 4L when the mute signal subjected
to the mute processing by the L channel ANC unit 11 is output from the mute speaker 4L. , Has a
role of performing correction processing on the mute signal. The L speaker correction unit 16
performs a correction process on the muffling signal so as to have an opposite phase to the
frequency characteristic of the muffling speaker 4L, thereby outputting the muffling signal
without being affected by the characteristics of the muffling speaker 4L. It becomes possible.
[0057]
The L speaker correction section 16 shown in the present embodiment performs correction
processing of the mute signal using the correction characteristic of the speaker as shown in FIG.
9A. The correction characteristic of the speaker shown in FIG. 9A indicates that the level value in
the vicinity of 120 Hz is amplified by about 10 dB and the level value in the vicinity of 500 Hz is
attenuated by about 6 dB.
[0058]
FIG. 9B shows the frequency characteristic example 41 of the mute signal immediately after the
filtering process is performed by the L channel ANC unit 11 (that is, before the correction
process is performed by the L speaker correction unit 16), and for the L speaker It is the graph
which showed the frequency characteristic example 42 after performing the correction |
amendment processing by the correction | amendment part 16. FIG. In the frequency
characteristic example 42 after the correction processing by the L speaker correction unit 16, the
level value near 120 Hz is amplified by about 10 dB as compared to the frequency characteristic
example 41 before the correction processing is performed, and around 500 Hz. Is attenuated by
about 6 dB, and has a frequency characteristic having the correction characteristic of the speaker
shown in FIG. 9A.
[0059]
Similarly, in the R speaker correction unit 17, when the muffling signal subjected to muffling
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processing by the R channel ANC unit 12 is output from the muffling speaker 4 R, the frequency
characteristic of the muffling signal is in accordance with the characteristic of the muffling
speaker 4 R It has a role of performing correction processing on the muffling signal so as not to
change. By applying a correction process to the muffling signal so as to be in reverse phase to
the frequency characteristic of the muffling speaker 4R in the R speaker correction unit 17,
outputting the muffling signal without being affected by the frequency characteristic of the
muffling speaker 4R Is possible.
[0060]
Like the L speaker correction unit 16, the R speaker correction unit 17 shown in the present
embodiment performs a correction process according to the correction characteristic of the R
speaker to the mute signal.
[0061]
The result of having performed a muffling process using the sound system 1 based on the
structure demonstrated above is demonstrated using drawing.
[0062]
FIG. 10 shows the L channel ANC unit 11 and the R channel ANC unit 12 in an acoustic system in
which the reference microphone noise correction unit 13, the L microphone noise correction unit
14, and the R microphone noise correction unit 15 are not provided. Example of frequency
characteristics in the vicinity of the error microphone 5L and error microphone 5R (ANC ON
shown in FIG. 10) in the case of operation and in the case of not operating the L channel ANC
unit 11 and the R channel ANC unit 12 The frequency characteristic example (ANC OFF shown in
FIG. 10) of error microphone 5 L in the case where processing is not performed and error
microphone 5 R vicinity is shown.
[0063]
A noise reduction process is performed using the L channel ANC unit 11 and the R channel ANC
unit 12 in an acoustic system in which the reference microphone noise correction unit 13, the L
microphone noise correction unit 14, and the R microphone noise correction unit 15 are not
provided. When this is done, as shown in FIG. 10, noise in the low frequency range (frequency
range of 170 Hz or less) can be effectively reduced, but noise in the middle high frequency range
(frequency range of 170 Hz or more) is sufficient. It shows the tendency that it is not possible to
demonstrate the noise reduction process.
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[0064]
On the other hand, in FIG. 11A, in the sound system 1 according to the present embodiment, the
noise is filtered by the noise correction unit 13 for the reference microphone and the noise
correction unit 14 for the L microphone is performed. Example of frequency characteristics near
the error microphone 5L when the L channel ANC unit 11 is applied to the error sound (ANC ON
shown in FIG. 11A), the noise correction unit for reference microphone 13, and for the L
microphone Example of frequency characteristics (ANC OFF shown in FIG. 11A) in the vicinity of
the error microphone 5L when the noise correction unit 14 and the L channel ANC unit 11 are
not applied (that is, when the mute processing is not performed) It shows.
[0065]
As shown in FIG. 11 (a), the frequency characteristic of the case where the noise reduction
processing is performed using the sound system 1 according to the present embodiment (ANC
ON shown in FIG. 11A) is the case where the noise reduction processing is not performed.
Compared to the frequency characteristics of (ANC OFF shown in FIG. 11 (a)), the noise level is
generally reduced (about 10 dB reduction) over the entire low band and the entire low band to
the middle high band. Is possible.
[0066]
Similarly, in FIG. 11B, in the acoustic system 1 according to the present embodiment, the noise
subjected to the filtering process by the reference microphone noise correcting unit 13 and the
filtered process by the R microphone noise correcting unit 15 are performed. An example of the
frequency characteristics near the error microphone 5R when the R channel ANC unit 12 is
applied to the error sound (ANC ON shown in FIG. 11B), the noise correction unit for the
reference microphone 13, and the noise for the R microphone The frequency characteristic
example (ANC OFF shown in FIG. 11B) in the vicinity of the error microphone 5R when the
correction unit 15 and the R channel ANC unit 12 are not applied (that is, when the mute
processing is not performed) is shown. ing.
[0067]
Also in FIG. 11 (b), the frequency characteristics in the case of performing the silencing process
using the acoustic system 1 according to the present embodiment (ANC ON shown in FIG. 11 (b))
are in the case of not performing the silencing process ( Compared to the frequency
characteristic of ANC OFF shown in 11 (b), it is possible to reduce the noise level (about 10 dB
reduction) as a whole over the entire low frequency band as well as the low frequency band and
the middle high frequency band. It has become.
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[0068]
As described above, in the sound system 1 according to the present invention, the frequency
characteristics of noise input to the L channel ANC unit 11 and the R channel ANC unit 12 are
flattened by the reference microphone noise correction unit 13 and the L channel After the
frequency characteristics of the error sound input to the ANC unit 11 for R channel or the ANC
unit 12 for R channel are flattened by the noise correction unit 14 for L microphone or the noise
correction unit 15 for R microphone, the L channel ANC unit 11 and R Since the mute processing
is performed by the channel ANC unit 12, it is possible to mute the frequency from the low band
to the middle high band entirely and uniformly with constant response time, and the user's left
and right ear positions (left and right It is possible to effectively reduce the noise in the vicinity
of the error microphone installation position).
[0069]
FIG. 12A shows the noise subjected to the filter processing by the reference microphone noise
correction unit 13 and the error sound subjected to the filter processing by the L microphone
noise correction unit 14 in the sound system 1 according to the present embodiment. On the
other hand, when the L channel ANC unit 11 is applied and the frequency characteristic example
in the vicinity of the error microphone 5 L (L channel ANC ON shown in FIG. 12A) and the R
channel ANC unit 12 are not applied. FIG. 12 shows an example of frequency characteristics (R
channel ANC OFF shown in FIG. 12A) in the vicinity of the error microphone 5R (in the case
where the mute processing is not performed).
[0070]
As shown in FIG. 12A, the noise in the vicinity of the left ear position (in the vicinity of the
installation position of the error microphone 5L) of the user who applied the L channel ANC unit
11 (that is, the noise reduction processing) Although noise reduction is realized overall over the
entire range from low to mid high by the functions of the correction unit 13, the L microphone
noise correction unit 14 and the L channel ANC unit 11, the R channel ANC unit 12 The noise in
the vicinity of the right ear position (in the vicinity of the error microphone 5R installation
position) of the user who did not apply (that is, no mute processing) could hardly realize the
silencing effect.
[0071]
On the other hand, in FIG. 12B, in the sound system 1 according to the present embodiment, the
noise subjected to the filtering process by the reference microphone noise correcting unit 13 and
the filtered process by the R microphone noise correcting unit 15 are performed. An example of
frequency characteristics near the error microphone 5R (R channel ANC ON shown in FIG. 12B)
when the R channel ANC unit 12 is applied to the error sound and the L channel ANC unit 11 is
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not applied FIG. 12 shows an example of frequency characteristics in the vicinity of the error
microphone 5L (L channel ANC OFF shown in FIG. 12B) in the case (that is, when the silencing
process is not performed).
[0072]
As shown in FIG. 12B, the noise in the vicinity of the right ear position (in the vicinity of the
installation position of the error microphone 5R) of the user who applied the R channel ANC unit
12 (that is, the noise reduction processing) Although noise reduction is realized overall over the
entire range from low to middle high frequencies by the functions of the correction unit 13, the R
microphone noise correction unit 15 and the R channel ANC unit 12, the L channel ANC unit 11
is realized. The noise in the vicinity of the left ear position (in the vicinity of the error
microphone 5L installation position) of the user who did not apply (i.e., no mute processing)
could hardly realize the mute effect.
[0073]
As shown in FIGS. 12 (a) and 12 (b), in the sound system 1 according to this embodiment, the
noise correction unit 13 for reference microphone and the noise correction unit for L
microphone regarding noise near the user's left ear Mute processing can be performed
effectively by the ANC unit 11 for 14 and L channels, and the noise correction unit 13 for
reference microphone, the noise correction unit 15 for R microphone, and the R channel for
noise near the user's right ear Since the noise reduction process can be effectively performed by
the ANC unit 12, the space can be divided into right and left, and independent noise reduction
control can be performed in the vicinity of the user's left and right ears.
For this reason, even if there is a difference in noise at the left and right ear positions, it is
possible to reduce noise from the low range to the middle high range with high accuracy and
efficiency according to each noise.
[0074]
The acoustic system according to the present invention has been described above in detail using
the drawings, but the acoustic system according to the present invention is not limited to the
above-described embodiment.
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It will be apparent to those skilled in the art that various changes and modifications can be
conceived within the scope of the appended claims, and of course these also fall within the
technical scope of the present invention. It is understood.
[0075]
For example, in the sound system 1 shown in the above embodiment, the reference microphone
noise correction unit 13, the L microphone noise correction unit 14, and the R microphone noise
correction unit 15 are based on the vehicle speed information acquired from the vehicle speed
sensor 9. Although a plurality of correction filters are selected and determined, for example,
when the sound system according to the present invention is used for a vehicle or the like having
a high soundproof effect, frequency characteristics of noise invading the vehicle interior
according to the vehicle speed Since the change may be difficult in some cases, the filter
processing may be performed using the same correction filter regardless of the vehicle speed.
[0076]
It is a figure showing a schematic structure of a sound system concerning an embodiment.
It is a block diagram showing a schematic configuration of a sound system according to an
embodiment.
It is the block diagram which showed schematic structure of the ANC section for reference
microphones concerning an embodiment.
(A) is a diagram showing the positional relationship between the muffling speakers 4L, 4R, the
error microphones 5L, 5R, and the user, and (b) is a graph showing acoustic characteristics of the
output sound of the muffling speaker 4L, (C) is a figure showing an acoustic characteristic in an
output sound of the muffling speaker 4R.
(A) shows the frequency characteristic example of the noise collected by the reference
microphone, the frequency characteristic example of the correction filter used for the filter
processing of the reference microphone noise correction unit, and the frequency characteristic
example of the noise subjected to the filter processing And (b) is a view showing an example of
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the frequency characteristic of the correction filter used for the filter processing of the noise
correction unit for the reference microphone for each vehicle speed.
(A) shows a frequency characteristic example of noise when the speed of the vehicle is 0 km / h
(so-called idling state), and (b) shows an example of the frequency characteristic of noise when
the speed of the vehicle is 50 km / h .
(A) shows the frequency characteristic example of the noise when the speed of the vehicle is 100
km / h, (b) is the noise collected by the reference microphone, and the filter processing by the
noise correction unit for the reference microphone An example of the frequency characteristic
before being performed and an example of the frequency characteristic after the filtering process
in the noise correction unit for the reference microphone are shown.
(A) is a figure showing an example of the frequency characteristic of the error sound collected by
the error microphone 5L, which is an example of the frequency characteristic before the filtering
process is performed by the L microphone noise correction unit, and the noise for the L
microphone An example of the frequency characteristic after the filter processing is performed in
the correction unit is shown, and (b) is a view showing an example of the frequency characteristic
of the error sound collected by the error microphone 5R, and the noise for R microphone An
example of frequency characteristics before filter processing is performed in the correction unit
and an example of frequency characteristics after filter processing in the noise correction unit for
R microphone are shown.
(A) is the figure which showed the correction | amendment characteristic of the speaker applied
in the correction | amendment part for L speakers, (b) is the frequency characteristic of the
muffling signal before performing the correction process by the correction | amendment part for
L speakers, L speaker It is the figure which showed the frequency characteristic after performing
the correction process by the correction part for.
Error microphone 5 L when the L channel ANC unit and the R channel ANC unit are operated in
an audio system in which the reference microphone noise correction unit, the L microphone
noise correction unit, and the R microphone noise correction unit are not provided. FIG. 14 is a
diagram showing an example of frequency characteristics near the error microphone 5R and an
example of frequency characteristics near the error microphone 5L and the error microphone 5R
when the L channel ANC unit and the R channel ANC unit are not operated.
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(A) shows an example of the frequency characteristics near the error microphone 5L when the
mute processing is performed by the L channel ANC unit and an example of the frequency
characteristics near the error microphone 5L when the mute processing is not performed by the
L channel ANC unit (B) shows an example of the frequency characteristic near the error
microphone 5R when the noise reduction processing is performed in the R channel ANC unit, and
in the case where the noise reduction processing is not performed in the R channel ANC unit. It is
the figure which showed the frequency characteristic example of error microphone 5R vicinity.
(A) shows an example of frequency characteristics near the error microphone 5L when muffling
processing is performed by the L channel ANC unit and an example of frequency characteristics
near the error microphone 5R when muffling processing is not performed by the R channel ANC
unit (B) shows an example of the frequency characteristic near the error microphone 5R in the
case where the mute processing is performed in the R channel ANC unit, and in the case where
the mute processing is not performed in the L channel ANC unit. It is the figure which showed
the frequency characteristic example of error microphone 5L vicinity.
Explanation of sign
[0077]
1 ... sound system 2 ... seat 3 ... (headrest part) 4L, 4R ... muffling speaker (speaker, L speaker, R
speaker) 5L, 5R ... error microphone (correction microphone, L microphone, R microphone) 6 ...
main body of the device Part 7 ... Reference microphone 8 ... Backrest part (of seat) 9 ... Vehicle
speed sensor 11 ... ANC part for L channel (acoustic correction means, acoustic correction means
for L channel) 12 ... ANC part for R channel (acoustic correction means, R channel For acoustic
correction means for noise) 13 ... noise correction unit for reference microphone (noise
correction means for reference microphone) 14 ... noise correction unit for L microphone (noise
correction means for L microphone) 15 ... noise correction unit for R microphone (noise for R
microphone Correction means 16 ... L speaker correction unit 17 ... R speaker correction unit 20
... delay unit 21 ... sound correction unit 22 ... L MS unit 23 ... FIR filter unit 24 ... Multiplication
unit
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