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JPH0591025

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DESCRIPTION JPH0591025
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
apparatus for adjusting acoustical frequency characteristics in a relatively narrow space such as
a car room.
[0002]
2. Description of the Related Art A booming noise is generated in a narrow space such as a
passenger compartment. A roaring sound is a sound that has a relatively low frequency and
squeezes the ear.
[0003]
FIG. 6 shows the sound pressure level with respect to the frequency of the noise generated in the
passenger compartment. When it tries to listen to music etc. with a sound reproduction
apparatus by a muddy sound, it is accompanied by a sense of discomfort. In order to eliminate
the booming noise, adjustment of frequency characteristics is performed.
[0004]
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1
There are parametric equalizers and graphic equalizers as devices for adjusting frequency
characteristics. The parametric equalizer is variable in center frequency f, gain G, and sharpness
Q (Q value), and by adjusting each of these parameters, desired frequency characteristics are
obtained. In the graphic equalizer, the center frequency f and the sharpness Q are fixed. Instead,
the frequency band is divided into a plurality, and the gain G is made variable for each band, and
adjustment is performed to obtain desired frequency characteristics as a whole.
[0005]
In the above-mentioned prior art, not only the cancellation of the booming noise but also
adjustment of frequency characteristics for various purposes is possible. However, the
adjustment for eliminating the booming noise is complicated because there are many adjustment
points. In addition, once the number of passengers in the vehicle changes, even after adjustment,
the conditions for the generation of the booming noise also change, so complicated adjustments
must be made again.
[0006]
An object of the present invention is to provide a frequency characteristic adjusting device which
can eliminate the muffled sound on the acoustic characteristic of the space where the acoustic
device is installed by simple adjustment.
[0007]
SUMMARY OF THE INVENTION According to the present invention, a part of the frequency
characteristic of the acoustic output from an acoustic device is attenuated to compensate for
muddy sound on the acoustic characteristics of the space where the acoustic device is installed. A
frequency characteristic adjusting device characterized by:
[0008]
According to the present invention, a portion of the frequency characteristic of the acoustic
output from the acoustic device is attenuated.
By matching this band to the lingering sound of the acoustic characteristics of the space where
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the sound device is installed, the generation of the sound output that is the source of the
lingering sound is suppressed and compensated.
[0009]
[0009] Since the generation of unpleasant roaring sounds in the sense of hearing can be
suppressed by a simple operation of adjusting the frequency band, the sound output from the
sound device can be suitably listened to.
[0010]
FIG. 1 shows an acoustic device including a frequency characteristic adjusting device according
to an embodiment of the present invention, and FIG. 2 shows a partially attenuated frequency
band realized by the embodiment shown in FIG. The characteristics are shown, and FIG. 3 shows
the frequency characteristic adjustment operation.
An audio signal output from a music source 11 such as a cassette tape reproducing device, a
compact disk reproducing device, or a tuner is automatically adjusted in frequency band by an
equalizer 12 which is a frequency characteristic adjusting device.
This adjustment operation is started by operating the switch 13 for instructing start and stop
alternately to the start side.
[0011]
The frequency characteristic of the equalizer 12 is such that the gain is reduced at the frequency
f1 as shown in FIG. This characteristic is changed as shown in FIG. As described above, the bands
f2 to f3 in which a part of the frequency characteristic is attenuated are made to coincide with
the band of the booming sound on the acoustic characteristic in the vehicle compartment, and it
is determined whether or not the unpleasant feeling on hearing disappears.
[0012]
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3
This operation is carried out by continuously and repeatedly operating from the lower limit to
the upper limit of the frequency. The change rate of the frequency at this time is relatively low,
making judgment easy
[0013]
The switch 13 is operated to the stop side and stopped at the position where the unpleasant
feeling on hearing has disappeared.
[0014]
The operation of FIG. 3 is implemented by a digital signal processing circuit (abbreviated "DSP")
and an equalizer 12 including a microcomputer.
When the switch 13 is operated to the start side, the operation is started from step a1. At step
a2, the change of the center frequency f1 starts. As the intermediate frequency f1 changes, the
bands f2 to f3 also change. This change is relatively slow. If it is felt that a roaring noise has
come off, the switch 13 is operated to the stop side at step a3. When the operation to the stop
side is not performed in step a3, the process returns to step a2 and continues changing of f1.
When the operation is made to the stop side in step a3, the operation is ended in step a4.
[0015]
By such a simple operation, it is possible to attenuate the sound in the frequency band to be a
muffled sound on the acoustic characteristics and suppress the generation thereof. An acoustic
output in which generation of a mumbling sound is attenuated and whose generation is
suppressed can be suitably heard from the speaker 15 via the amplifier 14.
[0016]
As a method of adjusting the frequency band, in addition to the automatic operation by the
switch 13, a method of manually raising or lowering the frequency may be considered. The
equalizer 12 can of course be realized not only by digital signal processing as described above
but also by analog signal processing using an operational amplifier or the like.
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[0017]
As described above, when the frequency band component of the booming sound is attenuated in
the sound output, as shown in FIG. 5, in a relatively narrow space such as a cabin having the
frequency characteristic shown in FIG. It can eliminate the influence of mumbling noise. That is,
the bands f2 to f3 in which a part of the frequency characteristics are attenuated match the
bands f2 to f3 of the booming sound on the acoustic characteristic in the vehicle compartment,
and the frequency characteristic is adjusted to suppress the generation of the booming noise.
[0018]
As described above, according to the present invention, a part of the frequency characteristic of
the sound output from the acoustic device is attenuated to match this band to a muffled sound on
the sound characteristic. By simply performing a simple operation of adjusting the frequency
band, it is possible to suppress the generation of the booming sound and preferably listen to the
acoustic output from the acoustic device.
[0019]
Further, it is possible to easily carry out readjustment in accordance with the change in the
number and distribution of personnel in the space such as the vehicle interior.
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