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JPH0468699

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DESCRIPTION JPH0468699
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
method of emphasizing the bass of a music signal, and more particularly to a method of
emphasizing the bass without phase shift and unnecessary increase in midrange gain. <Prior Art>
In an audio apparatus, a pass boost circuit is provided to boost low frequency gain in order to
emphasize the bass of a music signal. Such a conventional pass boost circuit is composed of a
resistor and a capacitor, and emphasizes and outputs the low band of the input analog audio
signal. <Problems to be Solved by the Invention> However, in the conventional pass boost circuit,
the gain rises up to the unnecessary midrange, or phase rotation (phase delay) occurs, which
causes the sound quality to deteriorate. In view of the above, it is an object of the present
invention to provide a bass emphasizing method that does not raise around the phase or the
midrange. In the present invention, in the present invention, a rectangular wave generating a
rectangular wave signal based on the first filtering process for extracting the low-frequency
component of the music signal and the positive / negative of the first filtering process Generation
processing, division processing for dividing a rectangular wave signal into 1 / N, multiplication
processing for acquiring the first filter processing result at a predetermined sampling period, and
multiplying by 1 / N frequency division output, high frequency component included in
multiplication result The second filtering process is performed by adding the second filtering
process result to the original music signal. <Operation> A low frequency component (for
example, 100 Hz or less) of the music signal is taken out, a rectangular wave signal is generated
based on the sign (sign) thereof, and the rectangular wave signal is divided by 17N (for example,
1/2) to obtain 50 Hz. It is a square wave. In parallel with this, the first filter processing result is
fetched at a predetermined sampling cycle, 1 / N frequency-divided output (50 H 2 rectangular
wave) is multiplied, high frequency components included in the multiplication result are cut, and
the original music signal is obtained. In addition, it emphasizes the bass below 50Hz. As
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described above, since the music signal of the source is not altered, it is possible to eliminate the
gain rise around the phase and the midrange. FIG. 1 is a signal flow diagram of a DSP (digital
signal processor) for realizing the bass enhancement method according to the present invention,
and FIG. 2 is a waveform diagram of each part in the signal flow. In FIG. 1, reference numeral 10
denotes a digital input terminal (DIN) to which a digital music signal SND is input, 11 denotes a
first filter processing unit that compares a low frequency component 1 of the music signal SND,
for example, a signal component LSW of 100 Hz or less , 12 is a rectangular wave generation
processing unit that generates a 100 Hz rectangular wave signal RTS based on the positive /
negative (sine) of a signal component (100 Hz sine wave) LSW of 100 Hz or less which is the first
filter processing result; 13 is a 100 Hz rectangular wave A division processing unit that divides
the signal RTS into 17N (for example, 1/2), and outputs a 50 Hz square wave HRTS with a plus
peak of +1 and a minus peak of -1.
14 is an envelope generation unit which takes in the first filter processing result LSW at a
predetermined sampling cycle, calculates an average value of 30 samplings, and outputs an
envelope value (EVL); 15 shows an envelope di EV L 50 Hz square wave HRTs And a second filter
processing unit 16 for cutting the 50 Hz even-order harmonic component contained in the
multiplication result DTR and outputting a smooth 50 Hz signal component LSD. The second
filter processing unit 16 performs an FIR type low pass filter operation to remove even harmonic
components (l OOHz, 200 Hz, ...), thereby making it steep and have no group delay. A signal
having characteristics can be output. 17.18 is a level adjustment processing unit, 19 is an
addition processing unit which adds the second filter processing result LSD to the original music
signal SND, and 2o is a digital audio signal high strength terminal (DOUT). According to the bass
enhancement method of the present invention. (1) The low frequency component (for example,
100 Hz or less) LSW of the music signal SND is extracted, (2) a 100 Hz rectangular wave signal
RTS is generated based on its sign, and (3) the rectangular wave signal RTS is 1 A 50 Hz
rectangular wave signal HRTS is generated by frequency division by / N (for example, 1/2). (4) In
parallel with the above, the first filter processing result LSW is taken in at a predetermined
sampling cycle, (5) 30-sampling-averaged product (EVL) is multiplied by 50 Hz square wave
HRTS, and (6) Then, the 50H2 even harmonic component contained in the multiplication result
DTR is cut, and (7) the 50H2 signal LSD obtained by removing the even harmonic component is
added to the original music signal SND, 50 Hz or less Emphasize the bass of As described above,
according to the present invention, it is possible to emphasize the bass without touching the
music signal of the source, and it is possible to eliminate the lift of the gain around the phase of
the music signal or in the midrange. The reason why the first filter processing unit 11 takes
signal components of 100 Hz or less is that there are few signal components of 50 Hz or less
included in the music signal SND, and signal components of 100 Hz or less are easier to make It
is from. Although the above description has been given as emphasizing the low frequency region
of 50 Hz or less, the present invention is not limited to such a case. Further, in the above
description, when emphasizing 50 Hz or less, the component of 100 Hz or less is extracted and
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divided in half. However, the component of 200 Hz or less may be extracted and divided in 1/4.
As described above, according to the present invention, the low frequency component of the
music signal is taken out, a rectangular wave signal is generated based on the positive / negative
thereof, and the rectangular wave signal is divided by 1 / N to generate a low frequency
rectangular wave. In parallel with these, the low frequency component of the music signal is
taken in at a predetermined sampling period and multiplied by 1 / N frequency-divided output,
and the high frequency component included in the multiplication result is cut to obtain the
original music signal. In addition, since it was configured to emphasize the bass below the
predetermined frequency, it is possible to emphasize the component below the predetermined
frequency without touching the music signal of the source, raising the gain around the phase and
the midrange Can be eliminated.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a signal flow diagram of a DSP for realizing the bass enhancement method according to
the present invention, and FIG. 2 is a waveform diagram of each part in the signal flow diagram.
10 · · · Digital input terminal (D IN) 11 · · · First filter processing unit 12 · · · Square wave
generation processing unit 13 · · · Division processing unit 14 · · · Envelope generation processing
unit 15 · · Multiplication processing unit 16 · · · Second filter processing unit 19 Addition
processing unit
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