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JPH11225392

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DESCRIPTION JPH11225392
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
frequency characteristic correction method for correcting frequency characteristics such as a
sound field, and more particularly to determination of a frequency characteristic reference level.
[0002]
2. Description of the Related Art Conventionally, when measuring the frequency characteristics of
a sound field such as a listening room with a microphone, the measured sound pressure level
may be squeezed out depending on the characteristics of the sound field, or sudden extraneous
noise may be introduced. May not be stable. Therefore, in the case where the frequency
characteristic of the sound field is corrected to be flat using an acoustic device or the like, it is
necessary to previously determine the reference level on the frequency characteristic.
[0003]
For example, when measuring the frequency characteristics of a certain sound field,
conventionally, the sound level measuring instrument measures the level of the sound obtained
by sweeping the audio frequency band emitted to the sound field with a microphone as a
reference level (for example, frequency The measured level at the time of sound collection of a
1000Hz signal) 0 dB if both agree, otherwise it will be decibel units, eg +3 dB if it exceeds the
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reference level and -2 dB if it falls below Record the measurement data of the sound field with.
FIG. 3 shows an example of the frequency characteristic of the measured sound field.
[0004]
However, when the frequency characteristic of the sound field is measured as described above,
and representative of the data, the frequency characteristic of the sound field can be obtained by
using the level of a certain frequency as a reference. Since it is not flat, the sound pressure at the
time of reproducing the music signal changes before and after the correction. Also, if the
reference level is made wider than the current band division width, the measurement signal has
to be changed, so it can not be easily changed. Also, changing the measurement bandwidth will
change the frequency resolution.
[0005]
An object of the present invention is to provide a frequency characteristic correction method
which solves the above-mentioned conventional problems.
[0006]
According to a first aspect of the present invention, there is provided a frequency characteristic
correction method according to the first aspect of the present invention, wherein the first step of
logarithmically equally dividing the entire frequency characteristic band into a plurality of small
bands is disclosed. A second step of measuring the level of each small band, a third step of
selecting a predetermined number of consecutive small bands, and a fourth step of calculating an
average value of measurement results of the selected predetermined number of small bands It is
characterized in that it comprises a step and a fifth step of correcting the frequency
characteristic with the calculated average value as a reference level.
[0007]
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic block diagram showing
an embodiment of a sound field measurement system for implementing a frequency
characteristic correction method according to the present invention.
In FIG. 1, 1 is a measurement signal generator, 2 is a preamplifier, 3 is a sound field corrector, 4
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is a changeover switch, 5 is a power amplifier, 6 is a speaker, 7 is a microphone, 8 is a sound
field measuring device.
[0008]
The measurement signal generator 1 sweeps and outputs the audio frequency full band signal,
and the output signal is amplified by the preamplifier 2, power amplified by the power amplifier
5 through the terminal a of the changeover switch 4, and supplied to the speaker 6 Be done.
The sound emitted from the speaker 6 is collected by the microphone 7 and supplied to the
sound field measuring device 8.
[0009]
The sound field measuring device 8 compares the level of the sound collected by the microphone
7 with the reference level and records measurement data of the sound field.
[0010]
If the frequency characteristic of the measured sound field is not flat as shown in FIG. 3, then the
sound field measuring instrument 8 logarithms the entire band of the frequency characteristic of
the sound field to a plurality of small bands as shown in FIG. Divide equally, then measure the
level of each sub-band.
[0011]
Next, the sound field measurement device 8 selects a predetermined number of continuous small
bands, and gives an average value of only the measurement results of these small bands.
FIG. 2 shows the case where, for example, the small bands A to F are selected.
Next, the result obtained by the following equation, that is, the average value is determined as the
reference level. Reference level = (A + B + C + D + E + F) / 6
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[0012]
Next, the changeover switch 4 is switched to the terminal b side, the sound field corrector 3 is
inserted into the signal system, and a sweep signal of the audio frequency full band outputted
from the measurement signal generator 1 is emitted from the speaker 6. The sound field
frequency is adjusted by the sound field corrector 3 so that the sound level measured by the
sound field measurement device 8 matches the reference level obtained as described above over
the entire band. Correct the characteristics.
[0013]
After correction by the sound field corrector 3 as described above, when an input signal from any
source device is input to the preamplifier 2, through the sound field corrector 3, the changeover
switch 4, the power amplifier 5, and the speaker 6, The sound field frequency characteristics of
the emitted sound become substantially flat over the entire band.
[0014]
As described above, according to the present invention, since averaging is performed after
measurement of frequency characteristics such as a sound field, an appropriate reference level
can be obtained for the system simply by changing the location and number of small bands to be
averaged. , Can be easily changed.
Further, by using the average value of a predetermined band as in the prior art as the reference
value, the change in sound pressure when the music signal is reproduced before and after the
correction is eliminated.
Also, since the small bandwidth for measurement is constant (equal), the frequency resolution
does not change.
[0015]
According to the present invention, an appropriate reference level can be obtained when
correcting frequency characteristics such as a sound field.
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