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JP2008236025

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DESCRIPTION JP2008236025
An audio signal is adjusted in consideration of a sound pressure level perceived perceptually.
SOLUTION: A sound pressure level to be perceived sensuously changes according to the
frequency of sound. Therefore, the L signal and R signal are band-split by the filters 11 to 16 to
extract signals of frequency components in different frequency regions, and the amplification
factor setting units 18, 21 and 24 maximize the strengths of the signals of the respective
frequency components. A value is detected, and a value corresponding to each of the intensities
is set, and the multipliers 17, 19, 20, 22, 23, 25 set the signals of the respective frequency
components by the amplification factor setting units 18, 21, 24, respectively. The signals of the
plurality of frequency components amplified by multiplication are synthesized by the adder
circuits 26 and 28 and output. [Selected figure] Figure 1
Audio apparatus and audio signal processing method
[0001]
The present invention relates to an audio device and an audio signal processing method.
[0002]
For the audio device that performs conventional loudness control, for example, by specifying the
genre of music, the amplification factor of the low band and the amplification factor of the high
band are uniquely set from the volume of the entire band of the audio signal, and the
amplification factor In some cases, the waveform of the audio signal is adjusted and output.
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1
On the other hand, as an audio apparatus having a function of automatically adjusting the
waveform of an audio signal without specifying a genre of music, there has been one described in
Patent Document 1 below. Japanese Patent Application Laid-Open No. 6-177688 (FIGS. 1, 29,
30)
[0003]
The audio apparatus shown in FIG. 29 of Patent Document 1 performs level detection on the
input audio signal, amplifies the audio signal at an amplification factor set according to the level
detection result, and compresses the waveform and outputs the signal. Do.
[0004]
The audio apparatus shown in FIG. 30 of Patent Document 1 obtains an amplification factor
based on the level of the output signal, amplifies the input audio signal by that amplification
factor, compresses the waveform, and compresses the waveform to a low frequency signal The
component is extracted, and the low frequency component and the high frequency component of
the audio signal are combined to form an output signal.
[0005]
The audio apparatus shown in FIG. 29 of Patent Document 1 and the audio apparatus shown in
FIG. 30 of the same document both have the difference between the input audio signal and the
output signal, but both have all the signal levels of the entire band. Detect and perform waveform
compression accordingly.
Therefore, in the case of hard rock music having a large amplitude of low frequency components,
waveform compression may be performed based on high frequency components that do not
require waveform compression.
Therefore, the sound quality may be deteriorated or the sound may be weakened more than
necessary.
[0006]
Therefore, the audio apparatus shown in FIG. 1 of Patent Document 1 divides the input audio
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2
signal into high frequency components and low frequency components, and compresses the
waveform of low frequency components with an amplification factor based on the wave height of
low frequency components. And the low frequency component compressed is mixed with the
high frequency component.
[0007]
FIG. 5 is a diagram showing equal loudness curves for explaining the problems of the
conventional audio device.
The equal loudness curve is published in the international standard ISO 226, and is created by
connecting sound pressure levels (equal loudness levels) in which sounds of various frequencies
can be perceived as loudly with the level of a pure tone of 1 KHz. Frequency characteristic, which
is one of the most basic characteristics in hearing.
[0008]
According to the equal loudness curve, the level of perceived sound pressure differs according to
the frequency of the sound, and the sound with the same sound pressure level as the level of the
pure tone of 1 KHz also differs depending on the level of the pure tone. Also, at any sound
pressure, the sensitivity is very good at 3 to 5 KHz, but when the sound pressure level decreases,
the perceived sensitivity becomes extremely poor compared to the high sound.
[0009]
In this way, the sound pressure level perceived perceptually with respect to the sound pressure
level of sound changes in a complex manner. On the other hand, conventional audio devices do
not take into account the level of sound perceived perceptually, and are audio devices that
uniquely set the amplification factor of the low band and the amplification factor of the high
band, Patent Document 1 As shown in FIGS. 29 and 30, in the audio apparatus in which the
amplification factor is set from the volume of the entire band of the audio signal or the output
signal, fine setting according to the frequency of the sound can not be performed.
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[0010]
The audio apparatus shown in FIG. 1 of Patent Document 1 aims to prevent the deterioration of
the sound in the bass region, and only by detecting the level of the bass sound and setting the
amplification factor of the bass region. There was no adjustment in the whole range. As described
above, in the conventional audio apparatus, the audio signal can not be finely amplified in
consideration of the sound pressure level perceived perceptually, and there has been no
technically satisfactory one.
[0011]
The present invention is an invention made in view of such a present situation, and it is possible
to adjust an audio signal in consideration of a sound pressure level perceived perceptually, and it
is easy to hear and powerfully reproduce. It is an object of the present invention to provide an
audio device and an audio signal processing method that make it possible.
[0012]
In order to achieve the above object, an audio device according to a first aspect of the present
invention comprises: a plurality of filters for filtering an audio signal and passing signals of
frequency components of different frequency regions of the audio signal respectively; A plurality
of amplification means for respectively inputting the signal of the frequency component from
each of the filters and generating an amplified signal obtained by amplifying the sound indicated
by the signal of the frequency component, and showing the signal of the frequency component
output from each of the filters A plurality of amplification factor setting means for respectively
detecting the intensity of sound and setting the amplification factor of each of the amplification
means connected to the respective filters according to the intensity; Amplified signals output
from the plurality of amplification means And combining means for combining and outputting.
[0013]
Note that each amplification factor setting unit obtains the maximum value of the nearest time of
the intensity of the sound indicated by the signal of the frequency component sequentially output
by each filter, and sets the amplification factor based on the maximum value. It is also good.
Further, the combining means may add and output amplified signals output from the plurality of
amplifying means to the audio signal.
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[0014]
In order to achieve the above object, according to a second aspect of the present invention, there
is provided an audio signal processing method comprising: filtering processing of an audio signal
to extract signals of frequency components of a plurality of different frequency domains of the
audio signal; An amplification signal obtained by detecting the intensity of the sound indicated by
the signal of each frequency component, setting an amplification factor according to the
intensity, and amplifying the sound indicated by the signal of each frequency component with
the set amplification factor And a combining process for combining and outputting the amplified
signal.
[0015]
In the amplification processing, the maximum value of the nearest time of the intensity of the
sound indicated by the signal of each frequency component extracted in the filter processing may
be determined, and the amplification factor may be set based on the maximum value.
[0016]
Further, in the combining process, the amplified signal generated in the amplification process
may be added to the audio signal and output.
[0017]
According to the present invention, it is possible to adjust an audio signal in consideration of a
sound pressure level that is perceived perceptually, enabling easy-to-listen and powerful
reproduction.
[0018]
Hereinafter, embodiments of the present invention will be described in detail based on the
drawings.
First Embodiment FIG. 1 is a block diagram showing an audio apparatus according to a first
embodiment of the present invention.
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[0019]
This audio device is a device that performs loudness control on a left signal (hereinafter referred
to as L signal) and a right signal (hereinafter referred to as R signal) that are audio signals
indicating input sound, and includes two low-pass filters And 11, two band pass filters 13 and
14, and two high pass filters 15 and 16.
[0020]
The low pass filter 11 is connected to the input terminal IN1 to which the L signal is input, and
passes the signal of the frequency component of the low frequency region of the L signal by
filtering by digital signal processing.
The low pass filter 12 is connected to the input terminal IN2 to which the R signal is input, and
passes the signal of the frequency component of the low frequency region of the R signal by
filtering by digital signal processing.
[0021]
The band pass filter 13 is connected to the input terminal IN1 and passes the signal of the
frequency component of the intermediate frequency region higher than the low frequency region
of the L signal by filtering by digital signal processing.
The band pass filter 14 is connected to the input terminal IN2 and passes the signal of the
frequency component of the intermediate frequency region higher than the low frequency region
of the R signal by filtering by digital signal processing.
[0022]
The high pass filter 15 is connected to the input terminal IN1 and passes digital signal
processing filtering to pass a signal of a frequency component higher than the intermediate
frequency range of the L signal.
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The high pass filter 16 is connected to the input terminal IN2 and passes digital signal
processing filtering to pass a signal of a frequency component higher than the intermediate
frequency region of the R signal.
[0023]
The output terminal of the low pass filter 11 is connected to the multiplier 17 and to the
amplification factor setting unit 18.
The output terminal of the low pass filter 12 is connected to the multiplier 19 and to the
amplification factor setting unit 18.
The amplification factor setting unit 18 is means for setting a value by which the output signals
of the low pass filters 11 and 12 are multiplied by the multipliers 17 and 19, respectively.
[0024]
The output terminal of the band pass filter 13 is connected to the multiplier 20 and to the
amplification factor setting unit 21. The output terminal of the band pass filter 14 is connected
to the multiplier 22 and to the amplification factor setting unit 21. The amplification factor
setting unit 21 is means for setting a value by which the output signals of the band pass filters
13 and 14 are multiplied by the multipliers 20 and 22.
[0025]
The output terminal of the high pass filter 15 is connected to the multiplier 23 and to the
amplification factor setting unit 24. The output terminal of the high pass filter 16 is connected to
the multiplier 25 and to the amplification factor setting unit 24. The amplification factor setting
unit 24 is means for setting a value by which the output signals of the high pass filters 15 and 16
are multiplied by the multipliers 23 and 25.
[0026]
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2 (a) to 2 (c) are diagrams showing configuration examples of the amplification factor setting
units 18, 21, and 24, respectively. As shown in FIG. 2A, the amplification factor setting unit 18 is
connected to a peak hold circuit 18a for inputting a signal of a frequency component in a low
frequency domain sequentially given from the low pass filter 11 and the low pass filter 12 and a
peak hold circuit 18a. And a gain setting circuit 18b.
[0027]
The peak hold circuit 18a samples the value of the signal of the frequency component given by
the low pass filter 11 and the signal of the frequency component given by the low pass filter 12,
and the value of the signal of the frequency component given by the two low pass filters 11, 12
The larger one is selected as a candidate for the maximum value, and the selected value is
compared with the past maximum value held so far. If the value selected as the maximum value
candidate is larger than the past maximum value, the selected value is attenuated by a
predetermined amount as a new maximum value and held. If the value selected as the candidate
of the maximum value is equal to or less than the maximum value in the past, the maximum
value in the past is taken as a new maximum value, attenuated by a predetermined amount, and
held. When the maximum value is held, the old maximum value gradually decreases by
attenuating a predetermined amount, and the maximum value of the latest time is easily switched
to the new maximum value. That is, the peak hold circuit 18 a detects the closest maximum value
of the sound indicated by the signal of the frequency component given from the low pass filters
11 and 12. The gain setting circuit 18b receives the maximum value held by the peak hold circuit
18a, sets a value corresponding to the maximum value, and supplies the value to the multipliers
17 and 19. Here, the value given to the multipliers 17 and 19 by the gain setting circuit 18b is
easy to listen to the signal of the frequency component in the low frequency band given from the
low pass filters 11 and 12 to the multipliers 17 and 19 based on the above-mentioned equal
loudness curve. Is the value to be
[0028]
The amplification factor setting unit 21 includes a peak hold circuit 21a and a gain setting circuit
21b similar to the peak hold circuit 18a and the gain setting circuit 18b of the amplification
factor setting unit 18 as shown in FIG. 2B. The signal of the frequency component of the
intermediate frequency band output from each of the band pass filters 13 and 14 is input to the
peak hold circuit 21a.
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[0029]
The peak hold circuit 21a samples the value of the signal of the frequency component given from
the band pass filters 13 and 14, and the larger one of the values of the signals of the frequency
components given from the two band pass filters 13 and 14 is the maximum value. The selected
value is compared with the past maximum value held so far. If the value selected as the maximum
value candidate is larger than the past maximum value, the selected value is attenuated by a
predetermined amount as a new maximum value and held. If the value selected as the candidate
of the maximum value is equal to or less than the maximum value in the past, the maximum
value in the past is taken as a new maximum value, attenuated by a predetermined amount, and
held. The peak hold circuit 21 a detects the closest maximum value of the sound indicated by the
signal of the frequency component of the intermediate frequency band given from the band pass
filters 13 and 14. The gain setting circuit 21b receives the maximum value held by the peak hold
circuit 21a, sets a value corresponding to the maximum value, and supplies the value to the
multipliers 20 and 22. Here, the value given to the multipliers 20 and 22 by the gain setting
circuit 21b is the signal of the frequency component of the intermediate frequency band given
from the band pass filters 13 and 14 to the multipliers 20 and 22 based on the above-mentioned
equal loudness curve. It is a value to ease.
[0030]
The amplification factor setting unit 24 includes a peak hold circuit 24a and a gain setting circuit
24b similar to the peak hold circuit 18a and the gain setting circuit 18b of the amplification
factor setting unit 18 as shown in FIG. 2C. The signal of the frequency component of the high
frequency band output from each of the high pass filters 15 and 16 is input to the peak hold
circuit 24a.
[0031]
The peak hold circuit 24a samples the value of the signal of the frequency component given by
the high pass filters 15 and 16, and the larger one of the values of the signal of the frequency
component given by the two high pass filters 15 and 16 is a candidate of the maximum value.
The selected value is compared with the past maximum value held so far. If the value selected as
the maximum value candidate is larger than the past maximum value, the selected value is
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attenuated by a predetermined amount as a new maximum value and held. If the value selected
as the candidate of the maximum value is equal to or less than the maximum value in the past,
the maximum value in the past is taken as a new maximum value, attenuated by a predetermined
amount, and held. The peak hold circuit 24 a detects the closest maximum value of the sound
indicated by the signal of the frequency component in the high frequency band given by the high
pass filters 15 and 16. The gain setting circuit 24b receives the maximum value held by the peak
hold circuit 24a, sets a value corresponding to the maximum value, and supplies the value to the
multipliers 23 and 25. Here, the value given to the multipliers 23 and 25 by the gain setting
circuit 24b is easy to listen to the signal of the frequency component of the high frequency band
given from the high pass filters 15 and 16 to the multipliers 23 and 25 based on the abovementioned equal loudness curve. Is the value to be
[0032]
The output terminals of the multiplier 17, the multiplier 20 and the multiplier 23 are connected
to an adder circuit 26 which is combining means. The input terminal IN1 is also connected to the
adder circuit 26 via the amplifier 27.
[0033]
The output terminals of the multiplier 19, the multiplier 22 and the multiplier 25 are connected
to an adder circuit 28 which is a combining means. The input terminal IN2 is also connected to
the adder circuit 28 via the amplifier 29.
[0034]
Next, the operation of the audio device shown in FIGS. 1 and 2 will be described. The low pass
filter 11, the band pass filter 13, and the high pass filter 15 perform band division on the L signal
input to the input terminal IN1 as an audio signal, and the low frequency domain signal of the L
signal is the low pass filter 11 The signal of the frequency component of the intermediate
frequency range is output from the band pass filter 13, and the signal of the frequency
component of the high frequency range is output from the high pass filter 15.
[0035]
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The low pass filter 12, the band pass filter 14 and the high pass filter 16 perform band division
on the R signal input to the input terminal IN2 as an audio signal, and the low frequency domain
signal of the R signal is a low pass filter 12 The signal of the frequency component of the
intermediate frequency range is output from the band pass filter 14, and the signal of the
frequency component of the high frequency range is output from the high pass filter 16.
[0036]
The amplification factor setting unit 18 sequentially detects the maximum value of the sound
indicated by the signal of the frequency component in the low frequency domain given from the
low pass filters 11 and 12, sets a value corresponding to the maximum value, and multiplies the
multipliers 17 and 19. Give to.
The multipliers 17 and 19 multiply the value of the signal of the frequency component in the low
frequency domain by the value set by the amplification factor setting unit 18 and amplify it, and
give it to the addition circuits 26 and 28, respectively.
[0037]
The amplification factor setting unit 21 sequentially detects the maximum value of the sound
indicated by the signal of the frequency component in the intermediate frequency area supplied
from the band pass filters 13 and 14, and sets a value corresponding to the maximum value. Give
to 22. The multipliers 20 and 22 multiply the value of the signal of the frequency component in
the intermediate frequency domain by the value set by the amplification factor setting unit 21 for
amplification, and provide the same to the addition circuits 26 and 28, respectively.
[0038]
The amplification factor setting unit 24 sequentially detects the maximum value of the sound
indicated by the signal of the frequency component in the high frequency area given from the
high pass filters 15 and 16, sets a value corresponding to the maximum value, and multiplies the
multipliers 23 and 25. Give to. The multipliers 23 and 25 multiply the value of the signal of the
frequency component in the high frequency domain by the value set by the amplification factor
setting unit 24 and amplify it, and give it to the addition circuits 26 and 28, respectively.
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[0039]
The adder circuit 26 adds the L signal and the value of the signal of each frequency component
amplified by each of the multipliers 17, 20 and 23, and outputs the result from an output
terminal OUT 1. The adder circuit 28 adds the R signal and the value of the signal of each
frequency component amplified by each of the multipliers 19, 22, 25 and outputs the result from
an output terminal OUT 2.
[0040]
The audio device of the present embodiment having the above configuration has the following
advantages. (1) The L signal and R signal to be audio signals can be divided into bands, and the
amplification factor for amplifying the signal of each frequency component can be set based on
the intensity of the sound indicated by the signal of the frequency component of each band. For
this reason, according to the pitch of the sound, it is possible to finely adjust according to the
sound pressure level perceived sensuously.
[0041]
(2) The amplification factor setting units 18, 21 and 24 set the amplification factors of the
multipliers 17, 19, 20, 22, 23 and 25 based on the maximum value of the sound indicated by the
signal of each frequency component. , L and R signals can be reflected in the size of the sound,
and does not impair the force at the time of reproduction.
[0042]
(3) The amplification factor setting units 18, 21 and 24 sequentially obtain the maximum value
of the sound indicated by the signal of each frequency component in the most recent time, and
accordingly, the multipliers 17, 19, 20, 22, 23, 25 The amplification factor can be changed
dynamically because the amplification factor is set.
Second Embodiment FIG. 3 is a block diagram showing an audio apparatus according to a second
embodiment of the present invention.
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[0043]
In the first embodiment described above, the L signal and R signal are digital signals, and the
output signals output from the output terminals OUT1 and OUT2 are also digital signals.
However, the L signal and R signal are analog signals. The present invention is also applicable to
the case where the output signals output from the output terminals OUT1 and OUT2 are also
analog signals. In the audio apparatus of FIG. 3, the input L signal and R signal and the output
signals output from the output terminals OUT1 and OUT2 are analog signals. This audio
apparatus includes two low pass filters 31 and 32 corresponding to the low pass filters 11 and
12 of the first embodiment, two band pass filters 33 and 34 corresponding to the band pass
filters 13 and 14, and a high pass Two high pass filters 35, 36 corresponding to the filters 15, 16
are provided.
[0044]
The low pass filter 31 is connected to the input terminal IN1 to which the L signal is input, and
passes the signal of the frequency component of the low frequency region of the L signal by
filtering. The low pass filter 32 is connected to the input terminal IN2 to which the R signal is
input, and passes the signal of the frequency component in the low frequency domain of the R
signal by filtering.
[0045]
The band pass filter 33 is connected to the input terminal IN1, and passes the signal of the
frequency component of the intermediate frequency region higher than the low frequency region
of the L signal by filtering. The band pass filter 34 is connected to the input terminal IN2 and
passes the signal of the frequency component of the intermediate frequency region higher than
the low frequency region of the R signal by filtering.
[0046]
The high pass filter 35 is connected to the input terminal IN1, and passes the signal of the
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13
frequency component higher than the middle frequency region of the L signal by the filtering.
The high pass filter 36 is connected to the input terminal IN2 and passes the signal of the
frequency component higher than the intermediate frequency range of the R signal by the
filtering.
[0047]
The output terminal of the low pass filter 31 is connected to the amplifier 37 and to the
amplification factor setting unit 38. The output terminal of the low pass filter 32 is connected to
the amplifier 39 and to the amplification factor setting unit 38. The amplification factor setting
unit 38 is means for setting the amplification factor when amplifying the output signal of each of
the low pass filters 31 and 32 by the amplifiers 37 and 39.
[0048]
The output terminal of the band pass filter 33 is connected to the amplifier 40 and to the
amplification factor setting unit 41. The output terminal of the band pass filter 34 is connected
to the amplifier 42 and to the amplification factor setting unit 41. The amplification factor setting
unit 41 is means for setting the amplification factor when amplifying the output signal of each of
the band pass filters 33 and 34 by the amplifiers 40 and 42.
[0049]
The output terminal of the high pass filter 35 is connected to the amplifier 43 and to the
amplification factor setting unit 44. The output terminal of the high pass filter 36 is connected to
the amplifier 45 and to the amplification factor setting unit 44. The amplification factor setting
unit 44 is a means for setting the amplification factor when amplifying the output signal of each
of the high pass filters 35 and 36 by the amplifiers 43 and 45.
[0050]
FIGS. 4A to 4C are diagrams showing configuration examples of the amplification factor setting
units 38, 41, and 44. FIG. The amplification factor setting units 38, 41, 44 correspond to the
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amplification factor setting units 18, 21, 24 of the first embodiment. The amplification factor
setting unit 38 includes a peak hold circuit 38a for inputting the signal of the frequency
component in the low frequency domain sequentially given from the low pass filter 31 and the
low pass filter 32, and a gain setting circuit 38b connected to the peak hold circuit 38a. ing.
[0051]
The peak hold circuit 38a selects the larger one of the value of the signal of the frequency
component given from the low pass filter 31 and the value of the signal of the frequency
component given from the low pass filter 32 as the candidate of the maximum value, Compare
with the past maximum value held up to. If the value selected as the maximum value candidate is
larger than the past maximum value, the selected value is attenuated by a predetermined amount
as a new maximum value and held. If the value selected as the candidate of the maximum value is
equal to or less than the maximum value in the past, the maximum value in the past is taken as a
new maximum value, attenuated by a predetermined amount, and held. The gain setting circuit
38b receives the maximum value held by the peak hold circuit 38a, and applies a voltage value
corresponding to the maximum value to the amplifiers 37 and 39. Here, the voltage value given
to the amplifiers 37 and 39 by the gain setting circuit 38 b makes it easy to listen to the signal of
the frequency component in the low frequency band given from the low pass filters 31 and 32 to
the amplifiers 37 and 39 based on the above-mentioned equal loudness curve. It is a value for
[0052]
The amplification factor setting unit 41 includes a peak hold circuit 41 a and a gain setting
circuit 41 b. The signal of the frequency component of the intermediate frequency band output
from each of the band pass filters 33 and 34 is input to the peak hold circuit 41a.
[0053]
The peak hold circuit 41a selects the larger one of the values of the frequency component signals
supplied from the band pass filters 33 and 34 as a candidate for the maximum value, and selects
the selected value and the past maximum value held so far. Compare with. If the value selected as
the maximum value candidate is larger than the past maximum value, the selected value is
attenuated by a predetermined amount as a new maximum value and held. If the value selected
as the candidate of the maximum value is equal to or less than the maximum value in the past,
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the maximum value in the past is taken as a new maximum value, attenuated by a predetermined
amount, and held. The gain setting circuit 41b receives the maximum value held by the peak hold
circuit 41a, sets a voltage value corresponding to the maximum value, and applies it to the
amplifiers 40 and 42. The value given to the amplifiers 40 and 42 by the gain setting circuit 41 b
is a value for making it easier to listen to the signal of the frequency component of the
intermediate frequency band given from the band pass filters 33 and 34 to the amplifiers 40 and
42 based on the above-mentioned equal loudness curve. It is.
[0054]
The amplification factor setting unit 44 includes a peak hold circuit 44 a and a gain setting
circuit 44 b. The signal of the frequency component of the high frequency band output from each
of the high pass filters 35 and 36 is input to the peak hold circuit 44a.
[0055]
The peak hold circuit 44a selects the larger one of the values of the frequency component signals
supplied from the high pass filters 35 and 36 as the candidate of the maximum value, and selects
the selected value and the past maximum value held so far. Compare If the value selected as the
maximum value candidate is larger than the past maximum value, the selected value is
attenuated by a predetermined amount as a new maximum value and held. If the value selected
as the candidate of the maximum value is equal to or less than the maximum value in the past,
the maximum value in the past is taken as a new maximum value, attenuated by a predetermined
amount, and held. The gain setting circuit 44b receives the maximum value held by the peak hold
circuit 44a, sets a value corresponding to the maximum value, and supplies the value to the
amplifiers 43 and 45. The value given to the amplifiers 43 and 45 by the gain setting circuit 44 b
is a value for making it easy to listen to the signal of the frequency component in the high
frequency band given from the high pass filters 35 and 36 to the amplifiers 43 and 45 based on
the above-mentioned equal loudness curve is there.
[0056]
The output terminals of the amplifier 37, the amplifier 40 and the amplifier 43 are connected to
a summing circuit 46 which is combining means. The input terminal IN1 is also connected to the
adder circuit 46 via the amplifier 47.
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[0057]
The output terminals of the amplifier 39, the amplifier 42 and the amplifier 45 are connected to
a summing circuit 48 which is combining means. The input terminal IN2 is also connected to the
adder circuit 48 via the amplifier 49.
[0058]
Next, the operation of the audio device shown in FIGS. 3 and 4 will be described. The low pass
filter 31, the band pass filter 33, and the high pass filter 35 perform band division on the L signal
input to the input terminal IN1, and a signal of a frequency component in the low frequency
region of the L signal is output from the low pass filter 31. The signal of the frequency
component in the intermediate frequency region is output from the band pass filter 33, and the
signal of the frequency component in the high frequency region is output from the high pass
filter 35.
[0059]
The low pass filter 32, the band pass filter 34 and the high pass filter 36 perform band division
on the R signal input to the input terminal IN2, and a signal of a frequency component in the low
frequency region of the R signal is output from the low pass filter 32 The signal of the frequency
component in the intermediate frequency region is output from the band pass filter 34, and the
signal of the frequency component in the high frequency region is output from the high pass
filter 36.
[0060]
The amplification factor setting unit 38 sequentially detects the maximum value of the sound
indicated by the signal of the frequency component in the low frequency region supplied from
the low pass filters 31 and 32, sets a voltage value corresponding to the maximum value, Give to.
The amplifiers 37 and 39 amplify the signal of the frequency component in the low frequency
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domain with an amplification factor based on the voltage value set by the amplification factor
setting unit 38, and provide the same to the addition circuits 46 and 48, respectively.
[0061]
The amplification factor setting unit 41 sequentially detects the maximum value of the sound
indicated by the signal of the frequency component in the intermediate frequency area given
from the band pass filters 33 and 34, and sets a voltage value corresponding to the maximum
value. Give to 42. The amplifiers 40 and 42 amplify signals of frequency components in the
intermediate frequency region with an amplification factor based on the voltage value set by the
amplification factor setting unit 41, and provide the signals to the addition circuits 46 and 48,
respectively.
[0062]
The amplification factor setting unit 44 sequentially detects the maximum value of the sound
indicated by the signal of the frequency component in the high frequency region given from the
high pass filters 35 and 36, sets a voltage value corresponding to the maximum value, Give to.
The amplifiers 43 and 45 amplify the signal of the frequency component in the high frequency
region with an amplification factor based on the voltage value set by the amplification factor
setting unit 44, and provide the signal to the addition circuits 46 and 48, respectively.
[0063]
The addition circuit 46 adds the L signal and the value of the signal of each frequency
component amplified by each of the amplifiers 37, 40, 43, and outputs the result from an output
terminal OUT1. The addition circuit 48 adds the R signal and the value of the signal of each
frequency component amplified by each of the amplifiers 39, 42, 45, and outputs the result from
an output terminal OUT2.
[0064]
The audio device of the present embodiment described above has the same effects as the audio
device of the first embodiment in the case where the L signal and the R signal are analog signals,
and the output signals output from the output terminals OUT1 and OUT2 are also analog signals.
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Play.
[0065]
The present invention is not limited to the above embodiment, and various modifications are
possible.
For example, in the above embodiment, the frequency of the audio signal is divided into three
regions, but the number of band pass filters 13 and 14 or band pass filters 33 and 34 is
increased to divide the L signal and R signal into the above bands. It may be finer than the
embodiment. In the above embodiment, the stereo system is assumed to have two types of audio
signals, L signal and R signal, but it is also possible to make the audio signal correspond to one
type of monaural system.
[0066]
It is a block diagram which shows the audio apparatus concerning the 1st Embodiment of this
invention. It is a figure which shows the structural example of the gain setting part in FIG. It is a
block diagram which shows the audio apparatus which concerns on the 2nd Embodiment of this
invention. It is a figure which shows the structural example of the gain setting part in FIG. It is a
figure which shows equal loudness curves.
Explanation of sign
[0067]
11, 12, 31, 32 low pass filters 13, 14, 33, 34 band pass filters 15, 16, 35, 36 high pass filters 17,
19, 20, 22, 23, 25 multipliers 18, 21, 24, 38, 41 , 44 Amplification factor setting unit 26, 28, 46,
48 Addition circuit 27, 29, 37, 39, 40, 42, 43, 45, 47, 49 Amplifier
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