JPH07162998

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DESCRIPTION JPH07162998
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
on-vehicle acoustic device mounted on a car.
[0002]
2. Description of the Related Art In a typical prior art, speakers are respectively disposed on the
left and right sides in the interior of a car, and the volume of each speaker is adjusted at each
listening position such as a driver's seat, a passenger seat and a rear seat. So-called position
selector function to properly set the volume and delay time for each listening position. An
acoustic device provided is known.
[0003]
In such prior art, the angle between the axis of the loudspeaker and the straight line connecting
the loudspeaker and the listening position is different for each listening position, and therefore
depending on the directivity of the loudspeaker, There is a problem that the sound pressure
frequency characteristic changes at each listening position, and particularly when the angle is
large, the sound pressure level in the high region decreases.
Nevertheless, in the prior art, such correction of the sound pressure frequency characteristics for
each listening position is not performed, thus causing the deviation of the sound field and the
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deterioration of the sound image localization.
[0004]
An object of the present invention is to provide an on-vehicle acoustic device capable of always
obtaining an optimal frequency balance even when the listening position changes.
[0005]
SUMMARY OF THE INVENTION According to the present invention, there are provided
loudspeakers respectively disposed on the left and right sides of a plurality of listening positions
in a vehicle compartment of an automobile, acoustic sources for generating left and right
acoustic signals and providing them to the respective loudspeakers. At each listening position, a
delay circuit for delaying an audio signal given to a nearer speaker with reference to the speaker
far from the listening position so that the phase of sound matches, and at each listening position,
the sound from each speaker Equalizer circuit that corrects high frequency range of acoustic
signal so that pressure frequency characteristic becomes flat, and volume adjustment circuit that
corrects level of acoustic signal so that sound pressure level from each speaker becomes the
same at each listening position And an on-vehicle acoustic device.
[0006]
According to the present invention, speakers are respectively disposed on the left and right sides
in the vehicle compartment of a car, and an acoustic signal from an acoustic source is given to
each of the left and right speakers to enable stereo listening. Among a plurality of listening
positions, for example, the driver's seat, the front passenger seat, and the left and right rear seats,
one selected listening position, for example the driver's seat, sounds from the left and right
speakers at the listening position. Delaying the acoustic signal applied to the nearer speaker by
the delay circuit with reference to the speaker far from the listening position so that the phases
are matched at the left and right ears of the At each listening position, the sound pressure
frequency characteristic from each speaker is flat, that is, the larger the angle between the axis of
the speaker and the straight line connecting the speaker and the listening position, Similarly, the
high frequency band of the sound signal is corrected by the equalizer circuit so as to enhance the
high frequency band, and (c) the sound pressure level from each speaker becomes the same at
the selected listening position. Level by the volume control circuit.
In this way, it is possible to prevent the imbalance of the sound field and the deterioration of the
sound image localization caused by the asymmetrical stereo listening at each listening position in
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the vehicle interior, and to obtain the optimum frequency balance at each desired listening
position in the vehicle interior.
[0007]
DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is an electric circuit diagram of an
embodiment of the present invention.
The sound source 1 may be, for example, a radio receiver, and a reproduction device of recording
media such as a magnetic tape cassette and a compact disc, etc. The front left speaker SP1
provided in the passenger compartment 3 of the automobile 2 shown in FIG. The acoustic signals
FL, FR, RL, and RR for the front right speaker SP2, the rear left speaker SP3 and the rear right
speaker SP4 are derived from the lines 4 to 7, respectively.
[0008]
In FIG. 2, a driver's seat 8, a passenger seat 9 and a rear seat 10 are provided in a passenger
compartment 3, and positions for stereo listening are set in these seats 8, 9 and 10.
[0009]
Each acoustic signal from the acoustic source 1 passes through the lines 4 to 7 through the input
selector switches Si1 to Si4 and further to the driver mode electric circuit 11, front mode electric
circuit 12, rear mode electric circuit 13 and family mode electric circuit. Through the circuit 14,
through the output changeover switches So1 to So4, the amplification circuits A1 to A4
respectively apply to the speakers SP1 to SP4.
The input changeover switches Si1 to Si4 and the output changeover switches So1 to So4 are
switched in conjunction with each other. The driver mode electric circuit 11 functions to correct
and adjust the acoustic signal so that a sound field optimum for the driver at the driver's seat 8 is
reproduced, and the front mode electric circuit 12 at the passenger seat 9 The rear mode electric
circuit 13 is for forming the optimum sound field, and the rear mode electric circuit 13 is for
optimum formation of the sound field at the rear left or right seat 10, and the family mode
electric circuit 14 is The plurality of seats 8, 9, and 10 in the passenger compartment 3 function
to correct and adjust acoustic signals to form an optimal sound field as much as possible.
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[0010]
FIG. 3 is a plan view showing the passenger compartment 3 shown in FIG. 2 in a simplified
manner. From the left speakers SP1 and SP3 when the same sound signal is given to all the
speakers SP1 to SP4 in achieving a driver mode for forming an optimal sound field for the driver
15 seated on the driver's seat 8 In order to match the phase of the sound reaching the left ear of
the driver 15 and the phase of the sound reaching the right ear of the driver 15 from the right
speakers SP2 and SP4, moreover, the left and right ears The acoustic signals provided to the
speakers SP1 to SP4 are delayed by the delay circuits DL11 to DL14 provided in the driver mode
electric circuit 11 of FIG. In setting the delay time, of the speakers SP1 to SP4, of the distances
L1 to L4 from the driver's 15 at the listening position, an acoustic signal given to the speaker
SP3 which is the farthest is referred to as a reference. The delay time of the sound signal given to
the speaker SP3 is set to zero, and as the distance approaches the driver 15, the delay time is set
to be large. The delay times of the delay circuits DL11 to DL14 are as shown in Table 1.
[0012]
Here, L3> L1> L4> L2 (1) With regard to the sound pressure frequency characteristics of the
speakers SP1 to SP4, the axis lines 17 to 20 of the speakers SP1 to SP4 are at the listening
positions with the speakers SP1 to SP4. The sound pressure at the listening position changes in
accordance with the directivity of each of the speakers SP1 to SP4 in accordance with angles θ1
to θ4 formed by straight lines connecting the left and right ears of the driver 15. Each of the
speakers SP1 to SP4 has, for example, the same configuration, and has sound pressure frequency
characteristics shown in FIG.
[0013]
For the loudspeaker SP1, the line 21 shows the characteristic on the axis 17 of that loudspeaker
SP1. The speaker SP1 is previously configured so as to enhance the high region so that the sound
pressure frequency characteristic is as flat as possible at a position deviated from the axis 17.
The line 22 shows the characteristic when the angle θ1 shifted from the axis line 17 of the
speaker SP1 is 30 °, and it is understood that the sound pressure in the high region is lowered.
When the angle θ1 becomes 60 °, the characteristics of the line 23 are obtained, and the sound
pressure in the high region largely decreases. When the speaker SP1 shown in FIG. 4 is used, the
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equalizer circuit EQ11 is used to correct the high frequency band of the acoustic signal so that
the sound pressure frequency characteristic becomes flat to the driver 15 who is the listening
position. Provided. The equalizer circuit EQ11 functions to enhance the high frequency band so
that an approximately flat sound pressure can be obtained in the high frequency band of, for
example, 1.5 kHz or more of the acoustic signal supplied to the speaker SP1. Similarly, the
equalizer circuits EQ12 to EQ14 respectively corresponding to the speakers SP2 to SP4 also
function to correct the high frequency band corresponding to the angles θ2 to θ4. The
enhancement levels of the high regions of these equalizer circuits EQ11 to EQ14 are as shown in
the above-mentioned Table 1, and the characteristics of the respective equalizer circuits EQ11 to
EQ14 are indicated by lines 24 to 27 shown in FIG. At this time, the angles θ1 to θ4 are as
shown in the equation 2.
[0014]
θ4> θ3> θ2> θ1 (2) In order to correct the level of the acoustic signal so that the driver 15
has the same sound pressure level from each of the speakers SP1 to SP4, variable resistors VR11
to VR14 are provided, respectively. The amount of attenuation is set to increase as the distances
L1 to L4 become shorter, as shown in Table 1.
[0015]
The variable resistors VR11 to VR14, the delay circuits DL11 to DL14, and the equalizer circuits
EQ11 to EQ14 are cascaded or connected in series for each of the speakers SP1 to SP4 so that an
optimum sound field for the driver 15 is formed. , Preset.
The remaining electric circuits 12 to 14 also have similar configurations, and the delay time, the
high frequency correction characteristic, and the volume correction amount are preset according
to each listening position. Equalizer circuits EQ11-EQ14 can also be used together to correct
unwanted characteristic parts of the sound propagation characteristics of the passenger
compartment 3.
[0016]
FIG. 6 is an electric circuit diagram of another embodiment of the present invention. In this
embodiment, left and right acoustic signals are supplied from the acoustic source 1 to the digital
acoustic processing circuit 29 through the lines 4 and 5, and from this processing circuit 29,
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amplification circuits A1 to A4 for the respective speakers SP1 to SP4 are provided. Given to
each. Using input means 30, one of driver mode, front mode, rear mode and family mode is
selected, whereby processing circuit 31 implemented by a microcomputer or the like is stored in
memory 32 in advance. The delay time for each mode, the high frequency correction
characteristic, and the volume correction amount are read out and given to the processing circuit
29 so that the sound signal is calculated so that the optimum sound field is formed at the
listening position in each selected mode. To be done.
[0017]
As described above, according to the present invention, the speakers are disposed respectively on
the left and right sides in the vehicle compartment, and the left and right acoustic signals are
given to each speaker from the acoustic source, and the acoustic signals are delayed by the delay
circuit It is delayed and its level is corrected by the volume control circuit, and in particular, in
the present invention, at each selected listening position, the sound pressure frequency
characteristics from each speaker become flat, that is, the axis of the speaker As the angle formed
with respect to the straight line connecting to the listening position is large, the high frequency
range is lowered according to the frequency characteristics of the speaker, so the high frequency
range of the acoustic signal is enhanced and corrected by the equalizer circuit. It is possible to
correct the difference in the frequency characteristics, in particular the high frequency
characteristics, due to the difference in the directivity of the speakers coming from the speakers
to the listener at each listening position. Optimum frequency balance can be obtained, and
furthermore, the difference in sound propagation characteristics due to the shape in the
passenger compartment can be corrected, whereby the bias of the sound field and the
deterioration of sound image localization Will be able to prevent.
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