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JPH0541293

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DESCRIPTION JPH0541293
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
vehicle-mounted acoustic device, and more particularly to means for correcting the deterioration
of sound pressure characteristics due to the interference of the sound of two or more sound
sources.
[0002]
2. Description of the Related Art When a plurality of speakers such as front L and R channels and
rear L and R channels are sounded by a vehicle-mounted audio device, a phase shift occurs based
on the difference in distance from each speaker to the listening position. Depending on the
frequency, the phase is reversed and the sound pressure is reduced.
[0003]
In order to correct the deterioration of the sound pressure characteristic due to the interference
of the sound of two or more sound sources, as shown in FIG. 4 (a), for example, signals of rear L
and R channels are The phase was inverted by
[0004]
The phase frequency characteristic of the output of the phase shifter shown in FIG. 4 (a) is wide
over a wide range of phase changes as shown in FIG. 4 (b). As a result, the sound pressure
characteristic at the listening position is shown in FIG. As shown in FIG. 4 (c), the sound pressure
was reduced in a part of the frequency range.
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1
[0005]
SUMMARY OF THE INVENTION The present invention has been made in view of the abovementioned point, and the purpose of the invention is to consider only the bands in which the
sounds of a plurality of sound sources are in antiphase with each other. An object of the present
invention is to provide an on-vehicle acoustic device in which deterioration of sound pressure
characteristics due to interference of sound is corrected by phase inversion in one channel.
[0006]
SUMMARY OF THE INVENTION A narrow band phase inverter according to the present invention
inputs a signal having a bandwidth to a band pass filter and a band stop filter having the pass
band of the band pass filter as an attenuation band. The signal passed through the band pass
filter is phase inverted by a phase inverter and added to the signal passed through the band stop
filter by an adder to obtain a composite signal.
[0007]
The on-vehicle acoustic apparatus according to the present invention is an on-vehicle acoustic
apparatus for producing a plurality of loudspeakers, wherein one or more loudspeakers are
driven by a signal passing through the narrow band phase inverter.
[0008]
According to the narrow band phase inverter of the present invention, the signal passing through
the band pass filter is the signal of the attenuation band of the band elimination filter, and the
signal whose signal is inverted and passes through the band elimination filter And the resulting
signal is flat with two low gain bands compensated.
[0009]
Also, the output of the narrow band phase inverter is inverted in phase with respect to the input
signal in the attenuation band of the band stop filter, ie, in the pass band of the band pass filter.
[0010]
The narrow band phase inverter as described above is used for one channel of the vehiclemounted acoustic device to invert the phase of the gain reduction band due to the antiphase of
the sound, and the other channel does not change the phase. By driving the speakers of the
channel, gain reduction bands due to the antiphase are eliminated, and flat sound pressure
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2
characteristics can be obtained.
[0011]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A narrow band phase inverter and
an on-vehicle acoustic apparatus according to an embodiment of the present invention will be
described with reference to the drawings.
FIG. 1 is a plan view showing a speaker arrangement of an on-vehicle acoustic apparatus
according to an embodiment of the present invention.
As shown in the figure, front L channel speakers (FL) and front R channel speakers (FR) are
respectively disposed on the front left and right of the vehicle.
In addition, rear L channel speakers (RL) and rear R channel speakers (RR) are respectively
disposed on the left and right of the rear of the vehicle.
[0012]
An audio signal from a CD player or radio is processed by the signal processing apparatus shown
in FIG. 2 to drive the speaker shown in FIG.
As shown in FIG. 2, the signals of the front L channel and the front R channel of the audio signal
are amplified by the amplifier 6 and drive the speakers of the front L channel and the front R
channel without changing the phase.
[0013]
On the other hand, the signals of the rear L channel and rear R channel of the audio signal are
processed by the narrow band phase inverter 1 and then amplified by the amplifier 7 to drive the
speakers of the rear L channel and rear R channel.
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[0014]
The narrow band phase inverter 1 is composed of a band stop filter 2, a band pass filter 3, a
phase inverter 4 and an adder 5.
The band stop filter 2 and the band pass filter 3 receive the rear L channel and rear R channel
signals of the audio signal.
[0015]
The pass band of the band pass filter 3 is equal to the attenuation band of the band stop filter 2,
and the signal passed through the band pass filter 3 is phase inverted by the phase inverter 4
and the signal passed through the band stop filter 2 by the adder 5. Added to
[0016]
The frequency gain characteristic of the output of the adder 5 (the signal at point A in the figure)
is flat as shown in FIG. 3A, and the frequency phase characteristic of the same output is
predetermined as shown in FIG. 3B. There is a depression reaching -180 ° in the zone of
Such a signal is input to the amplifier 7.
[0017]
The frequency gain characteristic of the signal (signal at point B in the figure) input to the
amplifier 6 becomes flat as shown in FIG. 3C, and the frequency phase characteristic of the same
output is as shown in FIG. 3D. Flat.
In this manner, the speakers of the front L channel and the front R channel are driven by the
signal processing device and the signals are processed by the signal processing device, and a flat
sound pressure frequency characteristic as shown in FIG. 3E is obtained at the listening position.
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[0018]
FIG. 3 (f) shows the sound pressure frequency characteristics when neither a front signal nor a
rear signal uses a phase inverter.
The recessed portion shows that the gain is reduced due to the interference by the sound waves
of the opposite phase.
The horizontal axes of the graphs in FIGS. 3A to 3F indicate frequencies, and the lengths of unit
frequencies are the same.
[0019]
Although the embodiment has described the case in which the front and rear channels interfere
with each other, the invention is not limited thereto. For example, the present invention may be
applied to cases in which the respective front and rear L and R channels interfere with each
other. It can be used.
Also, phase inversion may be performed on the front side instead of on the rear side.
[0020]
According to the narrow band phase inverter of the present invention, flat sound pressure
characteristics can be obtained by inverting the phase by a desired narrow band and using it in a
vehicle-mounted acoustic device.
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