JP2000261900

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DESCRIPTION JP2000261900
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound field correction method and an acoustic apparatus for correcting a sound field in, for
example, a room of a vehicle.
[0002]
2. Description of the Related Art Conventionally, control techniques for adjusting the acoustic
characteristics of the interior of a vehicle have been proposed. As a representative control
technique, removal of standing waves (Japanese Patent Laid-Open No. 9-327086) and delay time
have been proposed. (Japanese Patent Application Laid-Open No. 10-161667) and the like.
[0003]
First, as described in Japanese Patent Laid-Open No. 9-327086, the technology of standing wave
removal picks up the sound output from the speaker as being close to the original sound, and
influences the influence of the reflected sound in the room. It forms the removed sound field and
picks up the sound output from the speaker immediately before that, and the sound pressure
level of the picked up sound is within ± 4 dB over substantially the entire audio frequency band
The sound pressure level of the sound collected at the desired sound receiving point is adjusted
by the second correction means so as to be within ± 4 dB over substantially the entire audio
frequency band. .
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According to this method, sound pressure level adjustment is performed on the sound
immediately after the output of the speaker, and a sound very close to the original sound
reflecting the influence of the increase in the sound pressure level in the low range can be
reproduced.
[0004]
Second, as described in Japanese Patent Laid-Open No. 10-161667, the technique for optimizing
the delay time measures the signal propagation time of the non-control band in the vehicle
interior acoustic space in a short time, and The delay time is set in the delay unit, and the
adaptive signal processing unit in the delay time determination unit performs adaptive signal
processing to simulate the signal propagation type of the non-control band in the vehicle interior
acoustic space with the adaptive filter, The coefficient / delay time search unit refers to the
coefficient value of the adaptive filter to obtain the peak position of the signal propagation type
impulse response, obtains the signal propagation time from the peak position, and the signal
propagation time of the control band and the signal propagation of the non-control band The
difference with the time is set as a delay time in the delay unit so that the audio signal in the
control band and the audio signal in the non-control band reach the observation point
simultaneously.
[0005]
However, the above-mentioned conventional control technology of acoustic characteristics does
not control all frequency characteristics of the listening point.
That is, in the case of the passenger compartment, there is a disadvantage that the control at the
passenger seat is insufficient although the frequency characteristic of the driver's seat can be
controlled.
[0006]
Also, the technology for optimizing delay time described in Japanese Patent Laid-Open No. 10161667 is to provide a second speaker for correction separately to the first speaker and correct
only the speaker for correction. Although it is required to correct all the speakers, there is a
disadvantage that there is no technology that can satisfy this.
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[0007]
Further, in the sound field correction system that has been put into practical use, there is a
disadvantage that the type of vehicle to be mounted is limited because a super woofer and a
large number of (for example, 5 or more) speakers are required.
[0008]
Then, this invention is made in view of this point, and makes it a subject to control a standing
wave in a listening position, and to provide a sound field amendment method and an acoustic
device which amends frequency characteristics.
[0009]
According to the sound field correction method of the present invention, a microphone is
installed at an arbitrary position in a room, acoustic characteristics at the position are measured,
the measured values are analyzed, and the analyzed values are used. By controlling the audio
signal supplied to the speaker installed at the predetermined position in the room, the standing
wave is controlled at an arbitrary listening position to correct the frequency characteristic.
[0010]
Further, according to the sound device of the present invention, the microphone installed at any
position in the room, the measuring means for measuring the acoustic characteristic at the
position, the analyzing means for analyzing the measured value, and the sound device installed at
the predetermined position in the room And controlling means for controlling an audio signal
supplied to the speaker based on the analyzed value, and controlling a standing wave at an
arbitrary listening position to correct a frequency characteristic. .
[0011]
Therefore, according to the present invention, the following actions are performed.
In order to set each digital filter of the control means, the adjustment disk is used to test
reproduce the random signal.
Next, the reproduction sound of this trial reproduction is picked up using each microphone and
converted to digital data, and then the digital data is taken into the system control circuit of the
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measuring means, and the system control circuit of the control means performs a predetermined
operation. Then, the coefficients of each digital filter are determined, and each digital filter is
subjected to acoustic processing.
[0012]
The FIR type digital filter of the control means is mounted equal to or more than the number of
speakers, and predetermined acoustic processing is performed by setting the coefficient value
supplied from the system control circuit of the control means.
For example, four digital filters are used to control the output sound of the four speakers.
In addition, four microphones are used to measure the acoustic characteristics for controlling the
output sound of the four speakers.
[0013]
DESCRIPTION OF THE PREFERRED EMBODIMENTS [Analysis of sound processing] Before
describing the present embodiment in detail, an outline of sound processing performed in the
present embodiment will be described.
In recent years, with the improvement of vibration resistance performance of in-vehicle audio
devices, the importance of the vehicle interior as an audio listening space has increased.
However, since the listening environment and acoustic characteristics of the home are
significantly different, research on the listening environment is widely conducted to improve
these. Also, methods for improving acoustic characteristics by graphic equalizers and adaptive
filters have been proposed and put into production. However, the proposal of the method of
examining the acoustic mode and improving the acoustic characteristics at all listening positions
has not been addressed so far.
[0014]
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The inventors of the present application compared experimental results with analysis results by
the finite element method using a vehicle interior model, and confirmed that acoustic
characteristics can be accurately obtained. Moreover, the acoustic mode was visualized and the
frequency characteristic was improved by the correction filter which considered the acoustic
mode.
[0015]
[In-room acoustic characteristics by finite element method] First, analysis of in-vehicle acoustic
characteristics was performed by finite element method. In order to clarify the accuracy of the
analysis model, a typical frequency response ratio function (FRRF) in the case where the vehicle
interior space is assumed to be a rigid wall in, for example, an acrylic 1/3 scale vehicle interior
model shown in FIG. Experiment and analysis were conducted. The observation plane is the
position of the passenger's ear, and the observation point is the left ear position of the rear seat
right side, the rear seat left side, the front seat right side, and the front seat left side (hereinafter
referred to as A, B, C, D points in order. ). The frequency examined was set to 600 [Hz] or less
(corresponding to 200 [Hz] or less in an actual vehicle) at which the basic acoustic mode in the
vehicle room appears in the low frequency range in audio.
[0016]
Next, the frequency characteristic of point A when the analysis model is brought close to the
actual vehicle in consideration of the sound absorption characteristics was determined. In the
analysis model, four speakers are arranged symmetrically on the left and right as shown in FIG.
2, and the admittances obtained from the specific acoustic impedance ratio of the actual vehicle
already known on the six sound absorption walls constituting the cabin space I applied the value.
In the following, we will study this characteristic.
[0017]
[Application of Correction Filter] If there is a node of a mode to be described later at the listening
position as in the front seat, that mode can not be reproduced. Moreover, it is difficult to make
frequency characteristics flat at a plurality of positions only by changing the speaker installation
position.
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[0018]
Therefore, in the present embodiment, a correction filter using inverse characteristics of
frequency characteristics of the speaker and the listening position is applied to flatten the
frequency characteristics. In the present embodiment, the frequency characteristics at four points
of A, B, C, and D are independently controlled by four speakers. By applying the correction filter,
the frequency characteristic of the cabin changes, and the frequency characteristic of the
position of the passenger's ear becomes flat. Also, the four sound pressure levels described above
approached constant. Specifically, by applying the correction filter, the sound pressure difference
in the observation plane could be stabilized from average 26 [dB] to 18 [dB] to 8 [dB].
[0019]
Thus, using the 1/3 scale model, the improvement of the frequency characteristic by the
correction filter was examined. By controlling the four speakers by applying the correction filter,
the frequency characteristics of the observation point of 200 Hz or less can be made flat and the
sound pressure difference in the observation plane can be reduced.
[0020]
[Configuration of Sound Device] The present embodiment will be described below. First, the
configuration of the acoustic device of the present embodiment will be described with reference
to FIG. The acoustic device of the present embodiment is applied to the case of correcting a
sound field in a room of a vehicle.
[0021]
Below, the structure of the optical disk reproduction part 10 as an audio apparatus is
demonstrated. In FIG. 1, in the signal processing system, the optical disk reproduction unit 10
performs an optical pickup 11 for reading a signal from the disk D, and an RF signal processing
circuit 14 for amplifying a signal read by the optical pickup 11 at high frequency and outputting
an RF reproduction signal. And a demodulation DSP 16 that performs processing such as error
correction on the RF reproduction signal and outputs an audio signal, an audio DSP 20 that
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performs predetermined acoustic processing on the audio signal, and an audio signal that has
been acoustically processed by the audio DSP 20 It is configured to include amplification circuits
31 to 34 for amplification, and speakers 3LF, 3RF, 3LB, 3RB which are disposed in the
compartment 2 of the automobile 1 and output reproduced sound.
[0022]
The audio DSP 20 is configured to have four digital filters 25 to 28 in order to control the output
sound of the four speakers 3LF, 3RF, 3LB, 3RB in the sound processing system.
[0023]
The optical disk reproducing unit 10 also includes four microphones 21 to 24 for measuring
acoustic characteristics for controlling the output sound of the four speakers 3LF, 3RF, 3LB, and
3RB in the measurement system and the control system. An amplifier (AMP) and an analog-todigital converter (A / D) 44 for amplifying an audio signal collected using the microphones 21 to
24 and converting it into digital data, and taking the converted digital data and performing
predetermined operations The system control circuit 41 which causes the digital filters 25 to 28
to perform acoustic processing by determining the coefficients of the digital filters 25 to 28 and
a key input operation corresponding to an instruction of the reproduction operation to the
optical disc reproduction unit 10 are performed The configuration includes an operation key
group 42 and a display 43 which is a display unit for displaying operation content.
[0024]
Further, in the servo system, the optical disk reproduction unit 10 extracts a clock signal at the
time of demodulation of the RF reproduction signal, and supplies a clock signal extracted to the
servo control circuit 15; The drive signal is supplied to the spindle motor 12 and the feed motor
13 based on the error signal (VE), and the drive signal is supplied to the 2-axis actuator of the
optical pickup 11 based on the tracking error signal (TE) and the focus error signal (FE). It has a
servo control circuit 15 that performs servo control by supplying it, a spindle motor 12 that
rotates the disk D, and a feed (thread) motor 13 that sequentially moves the optical pickup 11
from the inner circumferential direction to the outer circumferential direction of the disk D Is
configured.
[0025]
[Operation of Sound Device] The sound device configured in this way operates as follows.
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In FIG. 1, the optical pickup 11 reads a signal from the disc D.
The signal read by the optical pickup 11 is amplified at a high frequency by the RF signal
processing circuit 14, subjected to processing such as error correction by the demodulation DSP
16, and supplied to the audio DSP 20 as an audio signal.
Further, the RF reproduction signal at the time of demodulation is supplied to the reproduction
unit control circuit 17.
[0026]
The spindle motor 12 rotates the disk D, and the feed (thread) motor 13 moves the optical
pickup 11 sequentially from the inner circumferential direction to the outer circumferential
direction of the disk D. The servo control circuit 15 supplies drive signals to the spindle motor 12
and the feed motor 13 to perform servo control. The servo control circuit 15 generates a drive
signal based on the clock signal extracted from the RF reproduction signal in the reproduction
unit control circuit 17. In addition to the above, the reproduction unit control circuit 17 also
performs communication with the system control circuit (microcomputer (microcomputer)) 41
and controls mechanical mechanisms such as the loading mechanism and the feeding mechanism
of the disk D.
[0027]
When a key input operation corresponding to a reproduction operation instruction to the optical
disk reproduction unit 10 is performed by the operation key group 42, the above-described
reproduction operation of the disk D is executed after displaying the operation content on the
display 43 which is a display unit. .
[0028]
Specifically, the reproducing unit control circuit 17 generates a control signal based on a
command from the system control circuit 41 and supplies the control signal to the servo control
circuit 15.
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The servo control circuit 15 performs a servo control by supplying drive signals to the spindle
motor 12 and the feed motor 13 and further to the optical pickup 11. Thereby, the spindle motor
12 rotates the disk D, and the feed motor 13 sequentially moves the optical pickup 11 from the
inner circumferential direction of the disk D to the outer circumferential direction.
[0029]
At a predetermined position, a laser beam is irradiated from the optical pickup 11 to the disk D,
and focus servo is performed using the focus coil of the biaxial actuator of the optical pickup 11,
and tracking servo is performed using the tracking coil of the biaxial actuator of the optical
pickup 11. multiply. Thus, after each servo is applied, the signal is read and the digital audio
signal is reproduced.
[0030]
First, information such as the start / end address of the TOC (Table Of Contents) on the
innermost circumference of the disc D is read, and then the music (track) is reproduced. In this
way, playback of the track is performed, and digital audio data is supplied to the audio DSP 20. In
the audio DSP 20, predetermined audio processing to be described later is performed on the
audio data. Audio data subjected to acoustic processing by the audio DSP 20 is converted to an
analog audio signal, amplified by the amplification circuits 31 to 34, and reproduced from the
speakers 3LF, 3RF, 3LB, 3RB disposed in the compartment 2 of the automobile 1 It is output as a
sound.
[0031]
[Operation of Digital Filter] In this embodiment, especially, the digital filter 25 to 28 of the FIR
type is mounted in the audio DSP 20 at least equal to the number of the speakers 3LF, 3RF, 3LB,
3RB. Predetermined acoustic processing is performed by setting the coefficient value to be
supplied. In FIG. 1, the example which mounted four digital filters 25-28 in order to control the
output sound of four speaker 3LF, 3RF, 3LB, 3RB was shown. The four microphones 21 to 24 are
used to measure the acoustic characteristics for controlling the output sound of the four speakers
3LF, 3RF, 3LB, and 3RB.
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[0032]
In the actual control, first, in order to set each of the digital filters 25 to 28, a random signal is
subjected to trial reproduction using a disk for adjustment. Next, the reproduction sound of this
trial reproduction is picked up using each of the microphones 21 to 24 and converted to digital
data by an amplifier (AMP) and an analog-to-digital converter (A / D) 44, and then the system
control circuit 41 Digital data is taken in and predetermined operations are performed to
determine the coefficients of each digital filter, and each digital filter is subjected to acoustic
processing. The method of obtaining the characteristics of each digital filter will be described in
detail later.
[0033]
[Application Example] In the above-described embodiment, the system control unit 41 of the
optical disk reproducing unit 10 sets the coefficient values of the digital filters 25 to 28.
However, the present invention is not limited to this. The coefficient value may be read out from
the stored external semiconductor memory and supplied to the digital filters 25-28. Alternatively,
the coefficient value may be read out by reproducing the disk D on which the coefficient value is
recorded, and may be stored in a flash ROM or the like. The coefficient values may be recorded
and supplied to a floppy disk or magneto-optical recording medium (MO, MD).
[0034]
In the above-described embodiment, an example is shown in which four microphones 21 to 24
are used to measure the acoustic characteristics for controlling the output sound of the four
speakers 3LF, 3RF, 3LB, and 3RB. Not limited to this, measurement may be performed four times
at a position corresponding to four microphones using one microphone.
[0035]
[How to Find Characteristics of Each Digital Filter] Next, how to find the characteristics of each
digital filter will be described.
FIG. 2 shows a simulation model of the present embodiment. In FIG. 2, in order to analyze the
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acoustic characteristics by four speakers 3LF, 3RF, 3LB, 3RB on the left and right as a sound
source in the cabin space, a simulation surface 50 is set as shown in FIG. The simulation plane 50
in FIG. 2 is a plane corresponding to the height of the crew's ears in a real vehicle.
[0036]
FIG. 3 shows how to determine the characteristics of each digital filter according to the present
embodiment. For example, assuming that F1 to F4 are each sound source and X1 is a response
point in FIG. 3, for example, the response point X1 is expressed by the following equation by the
transfer function H ** established between each sound source F1 to F4 and the response point
X1. Is represented by
[0037]
X1 = H11 × F1 + H12 × F2 + H13 × F3 + H14 × F4
[0038]
Here, H ** is a transfer function H (S).
Therefore, the phase characteristics also need to be controlled. Furthermore, the terms are
treated as not subordinate to each other.
[0039]
Therefore, if similar equations can be considered for each response point (X1 to X4), the
determinant shown in the upper right of FIG. 3 is obtained. From this, the sound sources F1 to F4
are expressed as the determinant at the lower right of FIG. 3, and the characteristics of the sound
source can be obtained by solving the inverse matrix as X1 = X2 = X3 = X4 = constant. Assuming
that the frequency characteristics of the speakers 3LF, 3RF, 3LB, 3RB are flat, the sound sources
F1 to F4 have filter characteristics of the control system to be obtained. For example, the
frequency characteristic of each filter can be obtained by solving the above-mentioned
determinant by the least squares method or the like for each frequency.
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[0040]
[Example of actual setting] In the actual setting, for example, an M-sequence signal (pseudo
random signal) or the like is generated from a speaker, and a car interior is generated based on a
cross correlation between a microphone output (reproduction signal) and a response in the car
interior. Find the impulse response of The obtained impulse response is subjected to FET
operation to obtain frequency characteristics, and the frequency characteristics of the filter are
determined so as to satisfy the above-mentioned determinant. FIG. 10A shows the frequency
characteristic (target value) of the sound source on the driver's seat side obtained from the
measurement data obtained in this manner. The coefficients of the digital filter are set so as to
satisfy this frequency characteristic. FIG. 10B shows the frequency characteristics obtained by
appropriately selecting the coefficients of the digital filter with respect to the sound source on
the driver's seat side.
[0041]
[Simulation Result Example] As shown in FIG. 2, the simulation was performed by setting four
sound sources at four positions corresponding to the left and right front and rear speakers of the
vehicle. FIG. 4 shows the response of the driver's seat and the response of the front passenger's
seat in the non-filtered state of the present embodiment. Further, FIG. 5 shows the sound
pressure distribution at the frequency of the acoustic mode in the state where the filter of this
embodiment is not applied. FIG. 5 shows the sound pressure distribution with the front of the
model on the left side when the simulation surface 50 of FIG. 2 is viewed from above.
[0042]
When the sound sources are set to the same sound pressure (100 [dB]), a peak of about 30 [dB]
occurs at maximum in both the driver's seat shown in FIG. 4A and the assistant driver's seat
shown in FIG. It can be seen that the fluctuation is large. The modes (Mode) 1 to 10 shown in FIG.
5 correspond to the respective acoustic modes and indicate the respective standing waves. In
addition, the frequency of each mode is mode 1: 243 Hz, mode 2: 306 Hz, mode 3: 390 Hz, mode
4: 453 Hz, mode 5: 528 Hz, mode 6: 549 Hz, mode 7: 615 Hz, mode 8: 624 Hz, mode 9 : 636 Hz,
mode 10: 657 Hz (the same applies to the following figures).
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[0043]
FIG. 6 shows the response of the driver's seat and the sound source on the driver's side front
with the filter of this embodiment applied. FIG. 7 shows the sound pressure distribution at the
frequency of the acoustic mode in the filtered state of the present embodiment. In FIG. 7, the
response point (measurement point) is set to a black circle ● on mode 1. This point corresponds
to the positions of the left and right ears of the driver and the front passenger. In the response of
the driver's seat shown in FIG. 6A, it can be seen that the frequency characteristics are controlled
to be flat at the positions of the left and right ears. Here, although not particularly shown, similar
results are obtained in the front passenger seat. The sound source of the driver's seat shown in
FIG. 6B is the frequency characteristic of the filter of the sound source on the driver's seat side.
In the sound pressure distribution shown in FIG. 7, the sound pressure is generally uniform as
compared with the case without the filter, and the sound pressure at the measurement point (the
position of each passenger's ear) is controlled to be flat.
[0044]
FIG. 8 shows the response of the driver's seat and the sound source on the driver's side front in a
filtered state at another response point of the present embodiment. FIG. 9 shows the sound
pressure distribution at the frequency of the acoustic mode in the filtered state at another
response point of this embodiment. In FIG. 9, the response point (measurement point) is set to a
black circle ● on mode 1. This point corresponds to the position of the left ear of all the
passengers (four people). In the response of the driver's seat shown in FIG. 8A, it can be seen that
the frequency characteristics are controlled to be flat at the positions of the left and right ears.
The sound source of the driver's seat shown in FIG. 8B is the frequency characteristic of the filter
of the sound source on the driver's seat side. In the sound pressure distribution shown in FIG. 9,
non-uniformity of the sound pressure distribution is seen in modes 7 and 10. However, the sound
pressure is stable over all modes when it is limited to the measurement points (per position of
the passenger's ear) I understand.
[0045]
According to the sound field correction method of the present embodiment described above, the
microphones 21 to 24 are installed at arbitrary positions in the room 2, the acoustic
characteristics at the positions are measured, the measured values are analyzed, and the analyzed
values are used. By controlling the audio signals supplied to the speakers 3LF, 3RF, 3LB, 3RB
installed at predetermined positions in the room 2, the standing wave is controlled at an arbitrary
listening position, and the frequency characteristics are corrected. The frequency characteristics
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of the room can be changed to flatten the frequency characteristics of the observation position,
and the sound pressure level at the measurement position can be made close to constant, thereby
reducing the sound pressure difference in the observation plane. be able to.
[0046]
Further, in the sound field correction method of the present embodiment, since the measurement
position is placed at the listening position in the above, the frequency characteristic of the
position of the ear, which is the listening position of the listener, can be made flat. The sound
pressure level at the measurement position can be made close to constant, and this can reduce
the sound pressure difference in the observation plane.
[0047]
Further, in the sound field correction method according to the present embodiment, since the
frequency characteristics of the measurement points are corrected by controlling the frequency
characteristics of the speakers 3LF, 3RF, 3LB, 3RB as many as the above-described number of
measurement points, The frequency characteristics of an arbitrary listening position can be made
flat, and the sound pressure level at the measurement position can be made close to a constant,
whereby the sound pressure difference in the observation plane can be reduced.
[0048]
Further, in the sound field correction method according to the present embodiment, the
frequency characteristics of the listening position in substantially the entire area of the room 2
are corrected as described above, so that the frequency characteristics of all listening positions in
the room 2 can be made flat. Thereby, the sound pressure difference in the observation plane can
be reduced.
[0049]
Further, in the sound field correction method of the present embodiment, since the room 2 is the
room 2 of the vehicle 1 in the above, the frequency characteristic of the observation position is
flat in the cabin where standing waves are easily generated in the sound field. The sound
pressure difference in the observation plane can be reduced.
[0050]
Further, in the acoustic device of the present embodiment, the microphones 21 to 24 installed at
an arbitrary position in the room 2, the system control circuit 41 as a measuring unit for
measuring the acoustic characteristic at the position, and the measurement value System control
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circuit 41 as an analysis means to be used, the speakers 3LF, 3RF, 3LB, 3RB installed at
predetermined positions in the room, and the speakers 3LF, 3RF, 3LB, 3RB based on the analysis
values. And a system control circuit 41 as a control means for controlling an audio signal to
control the standing wave at an arbitrary listening position and correct the frequency
characteristic, thereby changing the indoor frequency characteristic to change the frequency of
the observation position The characteristics can be made flat, and the sound pressure level at the
measurement position can be made close to constant, thereby reducing the sound pressure
difference in the observation plane. It can be.
[0051]
Further, in the acoustic device of the present embodiment, since the measurement position by
the system control circuit 41 as the measurement means is installed at the listening position in
the above, the frequency characteristic of the ear position which is the listener's listening
position is made flat. In addition, the sound pressure level at the measurement position can be
made close to constant, which can reduce the sound pressure difference in the observation plane.
[0052]
Further, in the acoustic device of the present embodiment, in the above, the system control
circuit 41 as the control means has the same number of loudspeakers 3LF, 3RF, 3LB, 3RB as the
number of measurement points by the system control circuit 41 as the measurement means. By
controlling the characteristics, the frequency characteristics of the above-mentioned
measurement point can be corrected, so that the frequency characteristics of any listening
position can be made flat, and the sound pressure level at the measurement position can be made
constant. By this, the sound pressure difference in the observation plane can be reduced.
[0053]
Further, in the acoustic device of the present embodiment, the system control circuit 41 as the
control means corrects the frequency characteristics of the listening position in the substantially
entire area of the room in the above, and therefore the frequency characteristics of all listening
positions in the room Can be made flat, which can reduce the sound pressure difference in the
observation plane.
[0054]
Further, in the acoustic device according to the present embodiment, in the above, the system
control circuit 41 as the control means is the same as or the same as the computing means and
the number of speakers 3LF, 3RF, 3LB, 3RB for controlling the supplied audio signal. Since the
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above-described number of FIR digital filters 25 to 28 are provided, even in the case of adding
speakers, the number of FIR digital filters corresponding to the number of speakers is used to
flatten the frequency characteristics of any listening position. In addition, the sound pressure
level at the measurement position can be made close to constant, which can reduce the sound
pressure difference in the observation plane.
[0055]
Further, in the acoustic device of the present embodiment, in the above, since the calculating
means calculates the coefficients in the FIR type digital filters 25-28, the coefficients are set so as
to have the inverse characteristic of the transfer function of the sound source at the
measurement point. By computing, the frequency characteristic of any listening position can be
made flat, and the sound pressure level at the measurement position can be made close to
constant, thereby reducing the sound pressure difference in the observation plane. it can.
[0056]
Further, in the acoustic device of the present embodiment, since the room 2 is the room 2 of the
vehicle 1 as described above, the frequency characteristic of the observation position is made flat
in the passenger compartment 2 where standing waves are easily generated in the sound field.
Sound pressure difference in the observation plane can be reduced.
[0057]
According to the sound field correction method of the present invention, a microphone is
installed at an arbitrary position in a room, the acoustic characteristic at the position is
measured, the measured value is analyzed, and the room is determined based on the analyzed
value. By controlling the audio signal supplied to the speaker installed at the predetermined
position, the standing wave is controlled at an arbitrary listening position and the frequency
characteristic is corrected, so that the indoor frequency characteristic is changed, and the
observation position is The frequency characteristics of the above can be made flat, and the
sound pressure level at the measurement position can be made close to a constant, and thereby
the sound pressure difference in the observation plane can be reduced.
[0058]
Further, in the sound field correction method of the present invention, since the measurement
position is placed at the listening position as described above, the frequency characteristic of the
position of the ear, which is the listener's listening position, can be made flat. The sound pressure
level can be made close to constant, and thereby the sound pressure difference in the observation
plane can be reduced.
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[0059]
Further, according to the sound field correction method of the present invention, since the
frequency characteristics of the measurement points are corrected by controlling the frequency
characteristics of the same number of loudspeakers as described above, the frequency
characteristics of any listening position are flat. In addition, the sound pressure level at the
measurement position can be made close to constant, and thereby, the sound pressure difference
in the observation plane can be reduced.
[0060]
Further, in the sound field correction method of the present invention, since the frequency
characteristics of the listening position in the substantially entire area of the room are corrected
in the above, the frequency characteristics of all the listening positions in the room can be made
flat. There is an effect that the sound pressure difference in the observation plane can be
reduced.
[0061]
Further, in the sound field correction method according to the present invention, as described
above, since the room is the vehicle room, the frequency characteristic of the observation
position can be made flat in the cabin where standing waves are easily generated in the sound
field. This produces an effect that the sound pressure difference in the observation plane can be
reduced.
[0062]
Further, according to the acoustic device of the present invention, the microphone installed at
any position in the room, the measuring means for measuring the acoustic characteristic at the
position, the analyzing means for analyzing the measured value, and the sound device installed at
the predetermined position in the room And controlling means for controlling an audio signal
supplied to the speaker based on the analysis value, and controlling a standing wave at an
arbitrary listening position to correct a frequency characteristic, so that the room is indoors. The
frequency characteristics of the observation position can be changed to make the frequency
characteristics of the observation position flat, and the sound pressure level at the measurement
position can be made close to constant, thereby reducing the sound pressure difference in the
observation plane. The effect of being able to
[0063]
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Further, in the acoustic device of the present invention, since the measurement position by the
measurement means is placed at the listening position in the above, the frequency characteristic
of the position of the ear, which is the listener's listening position, can be made flat. The sound
pressure level at the position can be brought close to a constant level, which has the effect of
being able to reduce the sound pressure difference in the observation plane.
[0064]
Further, in the audio apparatus according to the present invention, in the above, the control
means corrects the frequency characteristics of the measurement point by controlling the
frequency characteristics of the same number of loudspeakers as the number of measurement
points by the measurement means. The frequency characteristic of the position can be made flat,
and the sound pressure level at the measurement position can be brought close to a constant, so
that the sound pressure difference in the observation plane can be reduced.
[0065]
Further, in the acoustic device of the present invention, since the control means corrects the
frequency characteristics of the listening position in the substantially entire area of the room in
the above, the frequency characteristics of all the listening positions in the room can be made
flat. As a result, the sound pressure difference in the observation plane can be reduced.
[0066]
Further, in the audio apparatus according to the present invention, in the above, since the control
means includes the arithmetic means and the number of FIR digital filters equal to or more than
the number of speakers for controlling the supplied audio signal, Also in the case of addition, the
frequency characteristic of an arbitrary listening position can be made flat by using the number
of FIR type digital filters corresponding to the number of speakers, and the sound pressure level
at the measuring position can be made constant. Thus, the sound pressure difference in the
observation plane can be reduced.
[0067]
Further, in the acoustic device of the present invention, in the above, since the computing means
computes the coefficients in the FIR type digital filter, by computing the coefficients so as to be
the inverse characteristic of the transfer function of the sound source at the measurement point,
The frequency characteristics of an arbitrary listening position can be made flat, and the sound
pressure level at the measurement position can be made close to a constant, thereby reducing
the sound pressure difference in the observation plane. .
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[0068]
Further, in the acoustic device according to the present invention, since the room is the room of
the vehicle as described above, the frequency characteristic of the observation position can be
made flat in the cabin where standing waves are easily generated in the sound field. Thus, the
sound pressure difference in the observation plane can be reduced.
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