JPH06121396

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DESCRIPTION JPH06121396
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to
vehicle-mounted audio, and more particularly to correcting the bias of the sound image with
respect to the asymmetrical arrangement of a plurality of speakers per listening position.
[0002]
2. Description of the Related Art Heretofore, there has been a listening position correction device
as a technique in such a field. In audio mounted on a vehicle, a plurality of speakers are
asymmetrically arranged like a stereo with respect to a listening position. For this reason, the
sound image formed by the plurality of speakers is biased. In this listening position correction
device, in order to correct the bias of the sound image generated due to the plurality of speakers
being arranged asymmetrically with respect to the listening position, temporal deviation of
propagation of sound waves from the plurality of speakers, bias of sound wave attenuation Is
adjusted by the delay and gain between multiple signals.
[0003]
However, since the conventional listening position correction device corrects each listening
position for each type of vehicle on which the audio is mounted, the time lag of the propagation
of the sound wave from the plural speakers, the sound wave Since the bias of attenuation is
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adjusted by the delay and gain between a plurality of signals, there is a problem that it can not be
easily coped with when the type of vehicle mounted can not be predicted like commercial audio.
That is, the arrangement of the plurality of speakers is different for each of the various vehicles,
and it is necessary to correct the asymmetry of the speakers with respect to the listening position
for each of the various vehicles.
[0004]
SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an
automatic listening position correction device which can be used regardless of the type of vehicle
on which the audio is mounted.
[0005]
SUMMARY OF THE INVENTION In order to solve the above problems, the present invention
corrects the bias of the sound image formed by a plurality of speakers arranged asymmetrically
with respect to the listening position and reproducing electric signals from the sound source. The
listening position correction apparatus includes a time difference correction delay unit, a level
difference correction attenuator, a sound wave propagation time measuring unit, a time
difference calculation unit, and a level difference calculation unit.
[0006]
The time difference correction delay unit is disposed in front of the speaker and corrects signal
delay to the speaker.
The level difference correction attenuator is disposed in front of the speaker to correct the signal
level to the speaker.
The sound wave propagation time measuring means detects the rise of the test sound signal
based on the test sound signal from the sound source, and measures each propagation time
between each of the plurality of speakers and the listening position.
[0007]
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The time difference calculation unit calculates the difference between the propagation times, and
sets the difference between the propagation times in the time difference correction delay unit as
the correction amount of the signal delay. The level difference calculation unit obtains the
distance between each speaker and the listening position from each propagation time, and sets
the distance for the signal level correction in the level difference correction attenuator from this
distance.
[0008]
According to the listening position automatic correction device of the present invention, the rise
of the test sound signal is detected on the basis of the test sound signal from the sound source,
and the propagation time between each of the plurality of speakers and the listening position is
detected. The difference between the propagation times is calculated, and the difference between
the propagation times is set as the correction amount of the signal delay in the time difference
correction delay unit, and the distance between each speaker and the listening position is
determined from each propagation time. When the attenuation of the sound wave, which is
inversely proportional to the square of the distance, is set in the level difference correction
attenuator as the correction amount of the signal level, the bias of the sound image when the
speakers are arranged asymmetrically with respect to the listening position Can be corrected,
and it becomes possible to obtain a normal stereo feeling.
[0009]
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a view showing a listening position automatic correction device according to an
embodiment of the present invention. As shown in the figure, the listening position automatic
correction device 20 is used by being incorporated into an audio 100 mounted on a vehicle as an
example. First, the audio 100 will be described. The audio 100 comprises a CD player, a radio
tuner, a cassette deck, etc., and a sound source 101 for outputting left and right stereo digital
signals, a D / A converter 102 for converting digital signals from the sound source 101 into
analog signals, 103 (Digital to Analog Converter) and the D / A converters 102 and 103 for
converting, respectively, power amplifiers 104 and 105 for driving a speaker, and the power
amplifiers 104 and 105, respectively. It has speakers 106 and 107 directed into the passenger
compartment 200 and attached to the left and right doors. A test signal such as a simple impulse
is used as the sound source 101 when correcting the listening position.
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[0010]
The listening position automatic correction device 20 is provided at an asymmetrical driver's seat
in the passenger compartment 200 or at a listening position (both ears) such as a passenger seat,
and captures test sound reproduced by speakers 106 and 107 and propagated in the passenger
compartment. Between the left and right microphones 1 and 2, the amplifiers 3 and 4 connected
to the microphones 1 and 2 respectively to amplify the electrical signal obtained by converting
the captured sound, and the sound source 101 and the D / A converters 102 and 103 for
conversion. The time difference correction delay units 5 and 6, which are provided on the
respective stages, and the level difference correction attenuators 7 and 8 provided in the
subsequent stage of the time difference correction delay units 5 and 6, and variable gain; The
delay time to be set in the time difference correction delay units 5 and 6 is calculated based on
the test sound of the sound source 101 connected to 3 and 4 and One level difference including
a rise detector and the time difference level difference calculation unit 9 for calculating a gain to
be set to the correction attenuator 7 and 8. Next, the rise detection and time difference / level
difference calculation unit 9 will be described.
[0011]
FIG. 2 is a diagram showing the configuration of the rise detection and time difference / level
difference calculation unit of FIG. The rise detection and time difference / level difference
calculation unit 9 shown in FIG. The sound wave propagation time means 90 is connected to the
sound source 101, and is connected to timers 91 and 92, which reset and start measurement of
time by generation of a test sound signal, and amplifiers 3 and 4, respectively, and captured by
the left and right microphones 1 and 2. To detect the rising of the test sound and to stop the time
measurement of the timers 91 and 92 by the rising signal. The rising edge detection units 93 and
94 determine the threshold VR at a level lower than the rising edge of the test sound signal, and
detect the point at which the test sound signal first exceeds the threshold as the rising edge.
Alternatively, the first peak beyond the threshold may be taken as the rising edge.
[0012]
FIG. 3 is a diagram for explaining the time required for sound waves to propagate between the
left and right speakers and the left and right microphones. As shown in the figure (a), in the timer
91, the measurement time is started by the sound source 101, and the measurement time tR
obtained when the measurement time is stopped by the rise of the test sound signal detected by
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the rise detection unit 93 is obtained. It is the time for the sound wave to propagate from the
position to the right microphone 2. Similarly, as shown in the figure (b), in the timer 92, the
measurement time is started by the sound source 101, and the measurement time is stopped by
the rising of the test sound signal detected by the rising detection unit 94. It is time for sound
waves to propagate between the speaker 107 and the left microphone 1.
[0013]
Next, the rise detection and time difference / level difference calculation unit 9 comprises a time
difference calculation unit 95. The time difference calculation unit 95 obtains the time difference
tL-tR from the measurement times tR and tL obtained by the timers 91 and 92, and the
difference between the delay amounts of the time difference correction delay units 5 and 6
becomes the time difference tL-tR. As you set the delay amount.
[0014]
The rise detection and time difference / level difference calculation unit 9 also includes a level
difference calculation unit 96. The level difference calculation unit 96 determines the distance
DR between the speaker 106 and the microphone 2 and the distance DL between the speaker
107 and the microphone 1 from the measurement times tR and tL obtained by the timers 91 and
92 as follows. . DR = tR x vDL = tL x v where v is the speed of sound.
[0015]
Further, assuming that the propagation attenuation amount which attenuates while propagating
the sound waves DR and DL is VR and VL, respectively, and the condition that the propagation
attenuation amount of the sound wave is due to diffusion is as follows. VR∝1 / DR 2 = 1 / (tR ×
v) 2 VL ∝1 / DL 2 = 1 / (tL × v) 2 The level difference calculating unit 96 sets one of the level
difference correcting attenuators 7 and 8 to a gain of 1. The ratio of VR and VL is set as the gain
on the other side. The time difference calculating unit 95 and the level difference calculating unit
96 are formed in a CPU (central processing unit).
[0016]
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FIG. 4 is a flowchart for explaining a series of operations of the rise detection and the time
difference / level difference calculation unit. In step 1 shown in the figure, it is determined
whether there is an external request for correction of the listening position. When the audio is
installed, it is requested as having the correction request. In step 2, if a correction request is
made, the time difference calculation unit 95 calculates the difference in propagation time as the
correction amount of the signal delay as described above, and sets it in the time difference
correction delay units 5 and 6.
[0017]
In step 3, the distance between each speaker and the listening position is obtained from each
propagation time as described above, and the attenuation of the sound wave inversely
proportional to the square of this distance is set in the level difference correction attenuator as
the signal level correction amount. . In step 4, if there is no correction request in step 1, it is
assumed that the correction is completed, and the reproduction sound from the sound source
101 such as a CD player, a radio tuner, a cassette deck, etc. is formed. In this way, it becomes
possible to automatically correct the deviation of the sound image at the listening position.
[0018]
As described above, according to the present invention, the rise time of the test sound signal is
detected based on the test sound signal from the sound source, and each propagation time
between each of the plurality of speakers and the listening position is detected. Measure the
difference of each propagation time, set the difference of this propagation time as the correction
amount of signal delay in the time difference correction delay unit, calculate the distance
between each speaker and the listening position from each propagation time, and this distance
The attenuation of the sound wave, which is inversely proportional to the square of, is set in the
level difference correction attenuator as the correction amount of the signal level, so that the
deviation of the sound image when the speakers are arranged asymmetrically with respect to the
listening position can be corrected. It becomes possible to get a feeling of normal stereo.
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