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JPH07111693

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JPH07111693
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
graphic equalizer which performs tone control adjustment of each frequency band by digital
signal processing.
[0002]
2. Description of the Related Art A graphic equalizer is a tone control device in which an audio
band is divided into several parts so that the level of each band can be enhanced or attenuated.
[0003]
FIG. 1 shows the characteristics of the graphic equalizer. For example, the levels of 32HZ, 64HZ,
125HZ, 250HZ, 500HZ, 1KHZ, 2KHZ, 4KHZ, 8KHZ, 16KHZ bands are enhanced or attenuated.
[0004]
By controlling the tone with such graphic equalizer, it is possible to adjust the expression of
music or sound with fine nuances according to taste, or to use as a simple filter such as cutting
the sound range more than necessary. There is.
[0005]
By the way, such tone control is usually performed by an analog circuit using a series resonance
circuit of L and C, but the tone control by digital signal processing using a DSP (digital signal
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processor) is It is also possible to do.
[0006]
In this case, it can be realized by relatively compact hardware as compared with an analog
circuit, and furthermore, it has an advantage that various functions can be realized by changing
only the software without much changing the hardware.
[0007]
However, when tone control is performed using the above-described DSP, as shown in FIG. 2, for
example, 32HZ, 64HZ, 125HZ, 250HZ, 500HZ, 1KHZ, 2KHZ, 4KHZ, 8KHZ, as shown in FIG.
Although the level of the 16 KHZ band is enhanced or attenuated, the peaking of each band
becomes strong, so that there is a problem that the sound may be heard as an audible touch.
[0008]
The present invention has been made in view of the above circumstances, and it is an object of
the present invention to provide a graphic equalizer that can perform tone control by digital
signal processing appropriately in terms of hearing.
[0009]
SUMMARY OF THE INVENTION In order to achieve the above object, according to the present
invention, an audio signal is divided into a plurality of frequency bands by digital filters provided
in accordance with the frequency bands to be divided, and each digital is A graphic equalizer in
which level adjustment of the divided frequency band is individually performed by changing a
multiplication coefficient of a filter multiplier, and performing level adjustment of an arbitrary
frequency band among the divided frequency bands. In addition to level adjustment of the
arbitrary frequency band, multiplication coefficient changing means is provided for changing the
multiplication coefficient of the multiplier of the digital filter at a predetermined level ratio for
extracting the frequency band adjacent to the arbitrary frequency band. It is characterized by
being.
[0010]
In the graphic equalizer according to the present invention, when performing level adjustment of
an arbitrary frequency band among divided frequency bands, a frequency band adjacent to the
arbitrary frequency band is combined with level adjustment of the arbitrary frequency band.
Since the multiplication coefficients of the multipliers of the digital filter for extracting the
signals are changed at a predetermined level ratio, the tone control characteristics of the
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respective frequency bands are the same as the frequency characteristics performed by the
conventional analog circuit. Since the tail portion of can be broadened and the peaking of each
band can be alleviated, the problem of being heard as an audible sound can be resolved in terms
of hearing.
[0011]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be
described in detail with reference to the drawings.
FIG. 3 shows one embodiment of the graphic equalizer of the present invention.
The digital filters shown in the same drawing are illustrated for the case of three 800 HZ, 1 KHZ
and 1.25 KHZ for convenience of explanation.
[0012]
As shown in the figure, the graphic equalizer is provided with digital filters 10, 20, 30 provided
in accordance with the frequency bands 800HZ, 1KHZ, 1.25KHZ to be divided.
[0013]
Each digital filter 10, 20, 30 is provided with one-sample delay circuits 11, 21, 31, multipliers
12a-12e, 22a-22e, 32a-32e, and adders 13, 23, 33.
[0014]
The multiplication coefficient changing unit 40 receives the determination information from the
switch operation determination unit 50 that determines the operation state from the switch unit
60.
The multiplication coefficient changing unit 40 determines the values of the multiplication
coefficients a0 to a4, b0 to b4 and c0 to c4 of the multipliers 12a to 12e, 22a to 22e and 32a to
32e based on the setting signal from the switch operation determination unit 50. change.
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The switch unit 60 is provided with frequency setting function keys 61 and 62, a level up
function key 63, and a level down function key 64.
[0015]
Subsequently, the operation of the graphic equalizer having such a configuration will be
described with reference to FIG. 4 to FIG.
[0016]
First, a frequency band to be leveled up is set by the frequency setting function keys 61 and 62
of the switch unit 60 (step 401).
After the frequency band to be leveled up is set, the leveling up function key 63 is pressed to
level up the set frequency band (step 402).
[0017]
When the level-up function key 63 is operated, the switch operation determination unit 50
determines the number of times of operation of the level-up function key 63, and divides this
number of operations by "3" (step 403).
The remainder is then determined.
If the remainder is "1", the selected pole is increased by 1 dB (steps 404 and 405).
That is, as shown in FIG. 5, assuming that the selection pole is 1 KHZ, adjacent frequency bands
1.25 KHZ and 800 HZ are respectively +1 and -1, and 1.6 KHZ and 630 HZ are respectively +2
and -2. There is.
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Further, this state is as shown in FIG.
Incidentally, the level down time is as shown in FIG. 6 (b).
[0018]
If the remainder is "2", the selected pole is further increased by 1 dB, and the selected poles +1
and -1 are each increased by 1 dB (steps 406, 407, and 408).
That is, at the time of level up, it is as shown in FIG.
Incidentally, the level down time is as shown in FIG. 6 (b).
[0019]
If the remainder is "0", the selected pole is further increased by 1 dB from the previous time, and
the selected poles +1 and -1 are each increased by 1 dB, and the selected poles +2 and -2 are
further increased by 1 dB (step 409, 410, 411). That is, at the time of level up, it is as shown in
FIG. Incidentally, the level down time is as shown in FIG. 6 (b).
[0020]
FIGS. 7 to 13 show frequency characteristics obtained by measuring the level-up state of the
above frequency band in accordance with the number of times of operation of the level-up
function key 63.
[0021]
That is, FIG. 7 shows a state in which the level up function key 63 is not pressed, and the
frequency characteristic is flat.
[0022]
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FIG. 8 shows the case where the level up function key 63 is operated once, and the frequency
band of 1 KHZ is raised by one level.
FIG. 9 shows the case where the level-up function key 63 is operated twice, and the frequency
bands of 800 Hz, 1 kHz, and 1.25 kHz are each raised by one level.
However, with regard to the 1 KHZ frequency band, two levels have been raised. FIG. 10 shows
the case where the level-up function key 63 is operated three times. The frequency bands of 630
Hz, 800 Hz, 1 kHz, 1.25 kHz, and 1.6 kHz are each raised by one level. However, three levels are
raised for the 1 KHZ frequency band, and two levels are raised for the 800 HZ and 1.25 KHZ
frequency bands.
[0023]
FIG. 11 shows the case where the level-up function key 63 is operated four times, and only the
frequency band of 1 KHZ is further raised by one level (four levels in total). FIG. 12 shows the
case where the level-up function key 63 is operated five times, and the frequency bands of 800
Hz, 1 kHz, and 1.25 kHz are further increased by one level. FIG. 13 shows the case where the
level-up function key 63 is operated six times, and the frequency bands of 630 Hz, 800 Hz, 1
kHz, 1.25 kHz, and 1.6 kHz are further increased by one level.
[0024]
Thus, in the present embodiment, when performing level adjustment of an arbitrary frequency
band among the divided frequency bands, a frequency band adjacent to the arbitrary frequency
band is combined with level adjustment of the arbitrary frequency band. Since the multiplication
coefficients of the multipliers 12a to 12e, 22a to 22e, and 32a to 32e of the digital filters 10, 20,
and 30 for extraction are changed at a predetermined level ratio, the tone control characteristic
of each frequency band can be obtained. Like the frequency characteristic performed by the
conventional analog circuit, the base of the frequency band can be broadened, and the peaking of
each band can be mitigated, so that the sound may be heard as an audible touch. It is eliminated.
[0025]
In the present embodiment, the level setting ratio of each digital filter 10, 20, 30 by the
multiplication coefficient changing unit 40 is 1: 2: 3: 2: 1. However, the present invention is not
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limited to this example. The level setting ratio may be suitably changed as 1: 3: 5: 3: 1.
[0026]
As described above, according to the graphic equalizer of the present invention, when performing
level adjustment of an arbitrary frequency band among divided frequency bands, in combination
with level adjustment of the arbitrary frequency band, Since the multiplication coefficient of the
multiplier of the digital filter for extracting the frequency band adjacent to this arbitrary
frequency band is changed at a predetermined level ratio, the tone control characteristic of each
frequency band is made by the conventional analog circuit. Like the frequency characteristics to
be performed, the base of the frequency band can be extended, and the peaking of each band can
be alleviated, so that the problem of hearing as an audible sound can be eliminated. Tone control
by digital signal processing can be performed appropriately on hearing.
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