JPH0392098

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DESCRIPTION JPH0392098
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
on-vehicle acoustic correction device for improving the acoustic characteristics of the interior of
a car. 2. Related Art In recent years, a vehicle-mounted acoustic correction device using a
loudness circuit and a graphic equalizer circuit has been used as a method of correcting a vehicle
interior acoustic characteristic that lacks bass, but means for changing the amplitude
characteristic! The present situation is that it is not taken into consideration. A conventional onvehicle acoustic correction device will be described below. FIG. 7 is a block diagram showing an
example of an on-vehicle acoustic reproduction system configured by using a conventional onvehicle acoustic correction device. 1 is an acoustic signal source such as a car radio, a car tape
deck, a car compact disc player, 2 is an equalizer circuit in which a resonant circuit is constituted
by a semiconductor inductor, 3 is a power amplifier, and 4 is a speaker. FIG. 8 is a circuit
diagram of the equalizer circuit 2 composed of the semiconductor inductor 6, two amplifiers 6
and 7, resistors 8, 9, 10 and 11, and a capacitor 12. FIG. 9 is an amplitude characteristic diagram
of the equalizer circuit 2. . The operation of the on-vehicle acoustic correction apparatus
configured as described above will be described below. First, the signal sent from the acoustic
signal source 1 is enhanced by the power amplifier 3 with the low range of the amplitude
characteristic emphasized in the equalizer circuit 2 shown in FIG. 8 as shown in FIG. It is
reproduced by the speaker 4. As a result, low-frequency sounds lacking are corrected and
reproduced only by the reproduction device without the conventional low-frequency correction
device, so that it is balanced with the mid-high frequency sounds and flat vehicle interior acoustic
characteristics are obtained. SUMMARY OF THE INVENTION However, in the above-described
conventional configuration, in order to emphasize the low region of the amplitude characteristic
with the equalizer circuit 2 in which the resonant circuit is constituted by the semiconductor
inductor 6, the amplifier 6 as shown in FIG. There is a problem that at least two of 7 are
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necessary and the circuit configuration becomes complicated. The present invention is intended
to solve the above-mentioned conventional problems, and it is an object of the present invention
to provide an on-vehicle acoustic correction device having a simple circuit configuration in which
an amplitude changing unit emphasizing the low range is realized by one amplifier. is there.
Means for Solving the Problem In order to solve the subject, the vehicle-mounted acoustic
correction apparatus of the present invention sets the Q of the high-pass filter to 1.0 or more
using a resistor, a capacitor and one amplifier as the amplitude changing means. In particular, it
comprises a noise filter which emphasizes the low region of the amplitude characteristic, a power
amplifier which amplifies the output of the noise filter, and a speaker which reproduces the
output of the power amplifier. It is.
Operation With this arrangement, it is possible to realize an amplitude characteristic in which the
low range is emphasized by a high pass filter constituted by one amplifier. Embodiment An
embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a
block diagram showing the configuration of an on-vehicle acoustic correction apparatus
according to an embodiment of the present invention. In FIG. 1, 13 is an acoustic signal source
such as a car radio, a car tape deck, a car compact disc player, 14 is a positive feedback high pass
filter composed of a resistor and a capacitor and one operational amplifier, 15 is a power
amplifier, 16 is It is a speaker. FIG. 2 is a circuit diagram of the positive feedback high pass filter
14. FIG. 3 is an amplitude characteristic diagram of the positive feedback high-pass filter 14. The
operation of the on-vehicle acoustic correction apparatus configured as described above will be
described below. Generally, the output of the acoustic signal source 13 is input to the positive
feedback high-pass filter 14. As shown in FIG. 2, the positive feedback type high pass filter 14 is
composed of a resistor 17, 18.1-9.20, a capacitor 21.22 and one operational amplifier 23, and
the transfer function is represented by the following equation . However, K = 1 + Ry / RshS =
j11ω, j = pω: angular frequency, j: imaginary number unit The low cutoff frequency of this
positive feedback type high pass filter 14 and Q indicating the sharpness of resonance are as
follows: It is shown by a formula. However, ωO = 2 • π • Fc, where the Q is 30 and the cutoff
frequency is eoHz, the resistance 17 is 3 3.0 1, the resistance 18 is 2 2.0 KJ; , The capacitor 21 is
0.1 μF, the capacitor 22 is 0.1 μF, and the resistor 19 is 39. By setting the OKg and resistance 2
o constants to 15 and O ml, respectively, as shown in FIG. 3, it is possible to give a peak in the
amplitude characteristics near the low cutoff frequency, and it is possible to set a peak at 400 HZ
or higher. A level difference of approximately 1 odB can be secured. In other words, the
amplitude characteristic of the positive feedback high pass filter 14 emphasizes the low range.
When the output passing through this positive feedback type high pass filter 14 is added to the
power amplifier 16 and reproduced by the speaker 16, it is equal to the on-vehicle acoustic
correction device composed of the equalizer circuit that requires two conventional amplifiers.
Since the range sound is corrected, it is balanced with the middle high high castle sound, and flat
vehicle interior acoustic characteristics are obtained. As described above, according to the
present embodiment, the amplitude changing means is configured by the positive feedback high
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pass filter 14 using the resistor and the capacitor and one operational amplifier, and the constant
of the resistor and the capacitor is adjusted to adjust the positive feedback high pass filter. By
setting the Q of 14 to 30, an amplitude characteristic in which the low range is emphasized can
be realized by one amplifier.
Other constants may be used for the resistor and the capacitor to determine the Q and cut-off
frequency of the positive feedback high-pass filter 14 in the above embodiment. As shown in FIG.
4, to set the Q to 2.0, the resistance 17 is 1.2 K (; j, the resistance 18 is 7 s l, the capacitor 21 is
0.27 μF, and the capacitor 22 is 0.27 μF. , Resistance 20 is 10 KJ; '. At this time, it is possible to
emphasize about edB low band at 60 Hz. Similarly, setting Q to 1.0 can emphasize a low band of
about 1 dB. Furthermore, as shown in FIG. 5, in order to increase the cutoff frequency without
changing Q, the constants of the capacitors 21 and 22 may be reduced, and to reduce the cutoff
frequency, the capacitors 21 and 22 may be reduced. Increase the constant of 22. Further, as
shown in FIG. 6, the resistance 17 is 33K, 2, the resistance 18 is 22KJ7, the condenser 21 is 01
μF, the capacitor 22 is 0.1 μF1 and the resistance 19 is 39K. 1; , And the resistance 20 is 15
Kg, the gain can be 11 (IB can be held in all frequency bands) with q set to 3.0. In this case, the
load on the voltage amplification circuit of the power amplifier 15 connected behind is reduced.
Further, when the resistors 17 and 18 and the capacitors 21 and 22 are equal to each other, Q
can be determined by the ratio of the resistors 19 and 2o, so that the setting of the constant can
be easily performed. In the above embodiment, although the high pass filter is the positive
feedback high pass filter 14 in the above embodiment, the positive feedback high bus filter 14
may be a multiple feedback high pass filter. The invention is characterized in that the amplitude
changing means is constituted by a high pass filter using a resistor and a capacitor and one
amplifier, and the constant of the resistor and the capacitor is adjusted to set the Q of the high
pass filter to 10 or more. Thus, it is possible to realize an excellent on-vehicle acoustic correction
device capable of arranging the amplitude characteristic emphasizing the.
[0002]
Brief description of the drawings
[0003]
1 is a block diagram of a vehicle-mounted acoustic correction apparatus according to an
embodiment of the present invention, FIG. 2 is a circuit diagram of the high-pass filter of FIG. 1,
FIG. 3 is an amplitude characteristic diagram of the high-pass filter of FIG. 4 is an amplitude
characteristic diagram when Q of the high-pass filter of FIG. 1 is changed, FIG. 6 is an amplitude
characteristic diagram when Q of the high-pass filter of FIG. 1 is constant, FIG. Amplitude
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characteristics when changing the gain of the high-pass filter in Fig. 1, Fig. 7 is a block diagram
of the conventional on-vehicle acoustic correction device, Fig. 8 is a circuit diagram of the
equalizer circuit in Fig. 7, and Fig. 9 is It is an amplitude characteristic view of the equalizer
circuit of FIG.
13 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · power amplifier, 17 ˜ 20 · · · · · · · · · · · · · · · · · ·. amplifier.
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