JP2006174081

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DESCRIPTION JP2006174081
PROBLEM TO BE SOLVED: To improve reproduction characteristics of a small volume signal from
a speaker. SOLUTION: In the case where the linearity of the output level to the input signal is
substantially secured above the predetermined level and the output level to the input signal
decreases below the predetermined level as the input / output characteristic of the connected
speaker device, The correction processing to compensate for the decrease in the output level is
performed on the signal component below the predetermined level of the input audio signal, and
the gain to increase the signal component below the predetermined level at least in the low
region is reduced. It was set higher than the other frequency bands by setting the gain above
compensation. [Selected figure] Figure 2
Audio signal processing method and apparatus
[0001]
The present invention relates to an audio signal processing method and apparatus for performing
characteristic correction in the case of reproducing an audio signal from a speaker apparatus,
and is particularly suitable for use in a speaker apparatus for high fidelity reproduction capable
of reproducing high sound quality. It relates to technology.
[0002]
Conventionally, various configurations have been put to practical use as speaker devices for high
fidelity reproduction capable of high-quality sound reproduction.
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For example, there is a three-way speaker device in which a reproduction band of an audio signal
is divided into three bands of low, middle, and high bands, and separate speaker units are
prepared for each band. This 3-way speaker device can reproduce the input audio signal
faithfully from the low band to the high band by using a speaker unit for each band that has
good reproduction characteristics in each band. Generally, the reproduction characteristic is
better than that of a so-called full range type speaker unit in which audio of all bands is output
by one speaker unit.
[0003]
Further, in addition to the configuration for enhancing the reproduced sound of the speaker
device such as the 3-way configuration and the 2-way configuration as described above, the
characteristic of the audio signal itself supplied to the speaker device is It is also performed to
correct on the device side to improve the characteristics of the audio output from the speaker
device as a result. For example, an audio amplifier device that performs processing such as
amplification of an audio signal that drives a speaker device may perform correction called
loudness control. This loudness control performs correction processing that enhances the output
level compared to the midrange part with the bass part and the trebleband part, and corrects that
the low band and the high band are heard mainly when the volume is small. It is a thing.
[0004]
FIG. 11 shows an example of characteristics when the conventional loudness correction is
performed. As shown in FIG. 11, the low band fL is lifted, and the high band fH is also lifted.
[0005]
Patent Document 1 describes an example of a reproduction configuration when loudness
correction is performed. JP 2002-171589 A
[0006]
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However, since the loudness-controlled playback sound simply boosts the signal of a specific
frequency band almost uniformly regardless of the level, it is not strictly a reproduction that is
faithful to the input audio signal, but rather the input audio. It has been desired to develop a
speaker device capable of faithful reproduction to a signal. That is, since the conventional
loudness-controlled reproduction sound is reproduced by enhancing the sound which is hard to
hear when the volume is small, the bass and treble parts become easier to hear compared to the
reproduction sound without the loudness control, and the sound quality to some extent As shown
in FIG. 11, the signal component of a specific frequency band is uniformly enhanced at either a
small level or a large level, so that signal components that need not be enhanced are improved.
Also, the sound may be unnaturally reproduced as a result.
[0007]
Here, to explain the problem of the reproduced sound in the conventional speaker device, there
is a problem of a small amplitude signal as an example in the case where the reproduced sound
does not faithfully reproduce the input audio signal. That is, for example, as shown in FIG. 7A, it
is assumed that an input audio signal S1 having a waveform in which a waveform having a
relatively large amplitude and a waveform having a relatively small amplitude are continuous is
input to the speaker. At this time, the waveform of the output audio signal S2 from the speaker is
substantially the same as the input signal S1 for the waveform of relatively large amplitude, but
the amplitude of the waveform of relatively small amplitude is higher than that of the input
signal S1. It tends to be smaller. This is because a speaker unit having a general diaphragm
capable of outputting a relatively loud sound has poor reproduction characteristics of a small
volume signal with a small amplitude, and the linearity of the input / output characteristics of the
small volume signal ( Linearity) is not ensured.
[0008]
Similarly, for example, as shown in FIG. 7B, the input audio signal S3 of a waveform of relatively
large amplitude and the input audio signal S4 of a waveform of relatively small amplitude
temporally overlap each other, so that The audio signal S5 obtained by combining the two signals
S3 and S4 is output, but the output audio signal S6 having a waveform whose level is lower than
the waveform of the combined signal S5 is output from the speaker. For example, when the
sounds of various instruments are simultaneously reproduced as the audio to be reproduced
from the speaker, such as symphony, such an output state may occur.
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[0009]
Furthermore, for example, as shown in FIG. 7C, when there is an impulse signal in which the
amplitude of the signal of a specific single frequency gradually decreases as the input audio
signal S7, the waveform of the output audio signal S8 from the speaker Also, as the level
decreases, the followability deteriorates.
[0010]
In any of the examples shown in FIG. 7, as the output from the speaker, the output level of the
small volume signal having a small amplitude becomes smaller than the input signal level, and
the linearity of the small signal is not maintained.
When frequency analysis is performed on the state shown in FIG. 6, for example, the state shown
in FIG. 8 is obtained. The example of FIG. 8 is an example in which the sensitivities of the
fundamental wave f1 and the harmonics f2 and f3 that are harmonics of the fundamental wave
are analyzed. The fundamental wave f1 with a high level is output as it is, but the harmonics f2
and f3 whose levels are smaller than the fundamental wave have output sensitivities shown by a
solid line that is lower than the original level shown by a broken line. ing.
[0011]
FIG. 9 is a diagram showing output characteristics from low to high frequencies at multiple levels
of signal levels. FIG. 9 (a) is an ideal characteristic, and FIG. 9 (b) is an actual speaker output. It is
the figure which showed the characteristic. As shown in FIG. 9A, in an ideal state, it is assumed
that the four levels L1, L2, L3, and L4 have flat characteristics from low frequency to high
frequency at substantially equal intervals. At this time, as the output characteristics of the actual
speaker shown in FIG. 9 (b), for the levels L1, L2 and L3 having high output levels, output
characteristics substantially equivalent to the ideal characteristics can be secured, but the lowest
level The characteristic of L4 is a level which is lowered in any frequency band by the sensitivity
α from the originally necessary level.
[0012]
It is an input / output characteristic diagram of FIG. 10 that such a decrease in sensitivity is seen
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as a characteristic of a specific frequency. As shown in FIG. 10, the characteristic x of the broken
line in which the output level increases linearly with the increase of the input signal level to the
speaker has to be originally required. In this case, the level changes almost linearly, but below a
specific level, the movement of the diaphragm with respect to the input is bad, and the output
sensitivity to the input has a characteristic y of a curve that is very bad.
[0013]
Specifically, for example, assuming that the maximum level of listening by a general speaker is
70 to 100 spl (sound pressure level), a signal which is -30 dB to -60 dB lower than the maximum
level is correct for the maximum level- It means that the volume lowered by 30 dB to -60 dB is
not output (not proportional). Assuming that the volume of the output of the amplifier device is
reduced by 50 spl from 100 spl, the volume at around 50 spl should be obtained originally, but
in practice only 40 spl whose output is 10 spl lower is actually obtained, for example. It will not
be possible. That is, it means that linearity can not be accurately obtained, and it has been found
by analysis of the present inventor that it is one of the major causes for not obtaining satisfactory
sound quality.
[0014]
By the way, as the reproduction characteristics of the audio signal from the speaker device, if the
difference between the input and output levels of the characteristic y shown in FIG. 10 described
above can be corrected, the linearity of the input and output characteristics can be improved in
characteristics. Although it can, depending on the reproduction conditions, such correction alone
may not be sufficient.
[0015]
The present invention has been made in view of the foregoing, and it is an object of the present
invention to improve the reproduction characteristics of a small volume signal from a speaker.
[0016]
According to the present invention, the linearity of the output level with respect to the input
signal is substantially secured above the predetermined level as the input / output characteristic
of the connected speaker device, and the output level with respect to the input signal decreases
below the predetermined level. The correction processing to compensate for the decrease in the
output level is performed on the signal component below the predetermined level of the input
audio signal, and the gain to increase the signal component below the predetermined level at
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least in the low region is reduced. It is set to gain more than the compensation, and is higher than
other frequency bands.
[0017]
In this way, a signal with a relatively large amplitude above a predetermined level is not
enhanced, and the difference between the input / output level of a relatively small level signal
below a predetermined level resulting from the characteristics of the speaker device is corrected
It is possible to enhance low-level low-level signals that may be audible and audible.
[0018]
According to the present invention, a signal with a relatively large amplitude above a
predetermined level is not enhanced, and the difference between the input and output levels of a
relatively small level signal below a predetermined level resulting from the characteristics of the
speaker device is corrected. It is possible to enhance low-level low-level signals that may sound
deficient in hearing, and to improve playback sound quality without disturbing the overall
playback balance.
[0019]
In this case, as the correction processing, the gain for enhancing the signal component below the
predetermined level in the high region is increased, and the gain in the middle region is set to the
gain that compensates for the reduction in the speaker device. Even small level signals can be
enhanced well.
[0020]
In addition, a correction state in which only the decrease in output is compensated substantially
uniformly in almost all frequency bands output by the speaker device, and a correction state in
which the gain in excess of the reduction in a specific frequency band is set are selected. By
being able to set to, it is possible to select the state in which only the correction based on the
characteristics of the speaker device is performed and the state in which the low frequency range
is enhanced.
[0021]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1
to 6.
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FIG. 1 is a diagram showing an example of a system configuration according to the present
embodiment.
The present embodiment is an audio reproduction system connected with a speaker device, and
FIG. 1 is a diagram showing an example of the entire system configuration.
In this example, the audio signal source 10 is connected to the amplifier device 20, and the audio
signal source 10 reproduces an audio signal recorded (stored) in a medium such as a CD (disc) or
memory, and reproduces the audio signal. The audio signal to be output is supplied to the
amplifier device 20, and the amplifier device 20 performs processing to convert the audio signal
into an audio signal for driving the speaker device.
The amplifier device 20 includes the operation unit 20a, and can adjust the processing state of
the audio signal by the user operation of the operation unit 20a.
[0022]
In the case of this example, as audio signal processing in the amplifier device 20, correction
processing (dynamic range control processing to be described later) based on input / output
characteristics of the connected speaker device can be performed. In addition, loudness control
processing can be performed.
The on / off of each correction process can be set by the user operation of the operation unit
20a, for example.
The details of the specific correction process in these amplifier devices 20 will be described later.
[0023]
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Here, the audio signal output from the audio signal source 10 is a signal of two channels of an
audio signal for the left channel and an audio signal for the right channel.
The left channel audio signal output from the amplifier device 20 is supplied to the left channel
speaker device 30L for output, and the right channel audio signal is supplied to the right channel
speaker device 30R for output.
[0024]
The configuration of each of the speaker devices 30L and 30R will be described. Each of the
speaker devices 30L and 30R includes one speaker unit 31 (FIG. 2) as a speaker unit as sound
output means for outputting audio. Each of the speaker units 31 is a so-called full-franking type
speaker unit having a characteristic that is substantially flat in the audible band as a
characteristic seen from the output frequency band and that is outputted from low to high
frequencies There is a relatively large diaphragm and a relatively large speaker unit capable of
outputting a high volume signal. As for the speaker unit 31, since the diaphragm is relatively
large, the linearity (linearity) of the input / output characteristics of large signals above a
predetermined level is substantially maintained, and the linearity of the input / output
characteristics is not secured below the predetermined level. The output signal level is inferior to
the input signal level. That is, in the column of background art, the speaker unit having the
characteristic y described with reference to FIG. 10 is used. A speaker unit having such
characteristics is general as a speaker.
[0025]
In this example, in the audio reproduction system to which the speaker devices 30L and 30R
using the speaker unit 31 having such characteristics are connected, at the amplifier device 20
side that processes the audio signal supplied to the speaker devices 30L and 30R, Signal
characteristic correction is performed.
[0026]
FIG. 2 is a diagram showing a configuration for characteristic correction in the amplifier device
20 of the present example, and shows a connection configuration up to the speaker unit 31
constituting the speaker devices 30L and 30R.
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As shown in FIG. 2, an audio signal obtained at the audio signal input terminal 21 of the amplifier
device is supplied to an analog / digital converter 41 to be converted into a digital audio signal,
and the converted digital audio signal is Signal processor 42 is supplied. In this example, this DSP
42 is used as a means for correcting audio signal characteristics. The correction state of the DSP
42 is controlled by the control unit 44. The control state of the control unit 44 is set according to
the operation status of the operation unit 20a. Further, the control unit 44 is connected with a
memory 45 for storing data necessary for control, so that data on the correction state in the DSP
42 is also stored.
[0027]
As correction processing in the DSP 42, for example, signal components of all frequency bands in
digital operation processing are divided into signal components above a predetermined level and
signal components below a predetermined level, and nothing about signal components above a
predetermined level Do not perform correction processing. Then, for signal components less than
the predetermined level, correction processing is performed such that the increase rate becomes
higher as the output level becomes lower than the input level. Details of this correction process
will be described later.
[0028]
Then, the signal component above the predetermined level not subjected to the correction
process and the signal component below the predetermined level subjected to the correction
process are synthesized, and the synthesized signal is supplied to the digital / analog converter
43 to be an analog audio signal. Convert.
[0029]
The converted analog audio signal is supplied to the amplifier 24, amplified for driving the
speaker, and the amplified audio signal is supplied to the speaker unit 31 in the speaker devices
30L and 30R to output the audio signal (release Sound).
[0030]
Here, to describe audio signal correction processing in the amplifier device 20 of this example,
so-called dynamic range control processing can be performed to correct the badness of the input
/ output characteristics of the speaker unit 31 and the dynamic range control processing In
addition to the above, the loudness control process can be performed.
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[0031]
That is, the setting example of the audio signal correction processing state based on the
operation by the operation unit 20a of the amplifier device 20 of this example will be described
with reference to the flowchart of FIG. As a state, it is determined whether the dynamic range
control is set to ON (step ST11).
In this determination, when the dynamic range control is set to OFF, the control unit 44 does not
execute the correction process regarding the dynamic range control in the DSP 42 (step ST15).
[0032]
If it is determined in step ST11 that the dynamic range control is on, it is further determined
whether the loudness control is set to on (step ST12).
If the loudness control is set to OFF by this determination, the control unit 44 executes only the
dynamic range control processing as the correction processing in the DSP 42 (step ST13).
When the loudness control is set to ON, the control unit 44 executes the dynamic range control
process in the state where the loudness correction is performed as the correction process in the
DSP 42 (step ST14).
[0033]
Next, specific processing states of the dynamic range control processing selectively executed in
this manner and the dynamic range control processing in the state where the loudness correction
is performed will be described. First, dynamic range control processing in a state where loudness
correction is not performed will be described. In this dynamic range control processing, as a
speaker unit included in the speaker apparatus connected to the system of this embodiment, the
linearity of the input / output characteristics of large signals above a predetermined level is
substantially maintained, and the input / output below the predetermined level The linearity of
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the characteristic is not ensured, and the characteristic is that the output signal level is inferior to
the input signal level.
[0034]
FIG. 4 is a diagram showing an example of the characteristic corrected by the dynamic range
control process in the DSP 42. As shown in FIG. In FIG. 4, a characteristic a indicated by a broken
line is a characteristic in which the linearity is linearly proportional to the increase and decrease
of the input level and the increase and decrease of the output level, and is shown for reference.
The characteristic b shown by the solid line is an example of the characteristic corrected by the
DSP 42 of this example.
[0035]
As indicated by the characteristic b, the correction characteristic of the DSP 42 according to this
embodiment is a characteristic having linearity such that the increase and decrease of the input
level and the increase and decrease of the output level are linearly proportional in a range above
a predetermined level. (Ie, the input level and the output level are made equal). And in the range
below the predetermined level, the characteristic indicated by the curve where the increase rate
becomes high compared to the linear input / output characteristic a as the level is lower with
respect to the input level It is made to become.
[0036]
Here, with respect to the level position where the curve and the straight line of the characteristic
b change, the range of the level in which the linearity (linearity) of the input / output
characteristic is substantially maintained as the characteristic of the connected speaker unit 31,
and the input / output characteristic It is made to substantially coincide with the level of the
change point (that is, the above-mentioned predetermined level) with the range of the level at
which the linearity of the above is not secured. Specifically, when the peak level of the audio
signal is 0 dB, for example, when the range in which the linearity of the input / output
characteristics of the speaker unit 31 is secured is from 0 dB to -25 dB, -25 dB is set to a
predetermined level Then, the signal characteristic is not changed from 0 dB to about -25 dB, and
the curve of the characteristic b is set to about -25 dB or less. In addition, the characteristics for
determining the shape of the curve of the characteristic b curve are also set to characteristics in
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which the input and output characteristics of the input and output characteristics of the speaker
unit as shown in FIG. 10 are substantially reversed.
[0037]
Although the characteristic b shown in FIG. 4 shows the characteristic at a specific frequency, in
the case of this example, substantially the same characteristic is obtained in all the audible bands
that can be reproduced by the speaker unit 31. It is made to have it.
[0038]
Therefore, when the audio reproduction system of this example shown in FIG. 1 is installed, it is
possible to substantially linearly correct the badness of the input / output characteristics of the
speaker devices 31L and 31R connected to the system. The characteristic (characteristic b in FIG.
4) is set by the operation of the operation unit 20a.
Information of the set characteristic is stored, for example, in the memory 45 in the amplifier
device 20, and thereafter correction is performed with the set characteristic unless reset is
performed.
[0039]
FIG. 5 is a diagram showing a state in which an audio signal is output from the speaker devices
30L and 30R by correction with such characteristics as an output characteristic from low to high
in multiple signal levels. FIG. 5A is a view showing the output characteristics (that is, the output
characteristics not corrected) which the speaker devices 30L and 30R of this example have. FIG.
5A is the same as the speaker characteristic shown in FIG. 9B as the background art. That is, as
shown in FIG. 5A, for the levels L1, L2 and L3 having high output levels, an output characteristic
substantially equivalent to the ideal characteristic can be secured, but for the output
characteristic at the lowest level L4, The level is lowered in any frequency band by the sensitivity
α from the originally necessary level.
[0040]
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Here, as the output characteristics of the signal input to the amplifier device 20 by performing
the correction in the characteristic b shown in FIG. 4 in all the frequency bands by the correction
in the amplifier device 20, for example, FIG. As shown in), the output level does not change with
the input level for high levels L1, L2 and L3, but for the output characteristics of the lowest level
L4, the sensitivity increases from the original level by the sensitivity β, in any frequency band
Level. Here, the increased sensitivity β is set so as to substantially compensate for the sensitivity
α which is lowered by the speaker devices 30L and 30R.
[0041]
With the characteristics as described above, audio signals processed by the amplifier device 20
are output from the speaker devices 30L and 30R, whereby the characteristics of the audio
output from the speaker devices 30L and 30R are as shown in FIG. As shown, the four levels L1,
L2, L3, and L4 have flat characteristics from low frequency to high frequency at substantially
equal intervals, and are substantially equal to the ideal characteristics shown in FIG. 9A. Is a good
characteristic that matches regardless of the level in all frequency bands.
[0042]
Although the correction characteristics described above with reference to FIGS. 4 and 5 have
been described for the case where only the dynamic range control processing is performed, as
described above, the loudness control function is used as the correction processing in the DSP 42
of this example. It is also possible to perform attached dynamic range control processing.
FIG. 6 is a diagram showing the dynamic range control processing state with the loudness control
function in this example.
[0043]
Before describing the dynamic range control process with the loudness control function in this
example, to begin with, general loudness control which is conventionally known will be described
again with reference to FIG. The control performs correction for lifting the low band fL regardless
of the level, and performs correction for lifting the high band fH regardless of the level.
[0044]
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On the other hand, FIG. 6 shows the dynamic range control processing state with the loudness
control function of this example.
FIG. 6A is a graph showing the output characteristics of the signal input to the amplifier device
20. There is no change in the input level for the levels L1 and L2 with high output levels, but the
output characteristics of the lowest level L4 Is an elevated level by at least the sensitivity β from
the original level. Here, the point where the increased lowest sensitivity β substantially
compensates for the decreased sensitivity α in the speaker devices 30L and 30R is the same as
the dynamic range control processing without the loudness control function.
[0045]
Then, the sensitivity β is increased only in the substantially middle range of the frequency band
that the speaker devices 30L and 30R can reproduce, and for the low band and the high band, a
gain higher than the sensitivity β is set. To enhance the low and high frequencies that are
insufficient for hearing. However, it is different from the conventional loudness control in that
the gain enhancement here is performed only for signals of small amplitude (small volume)
below a predetermined level mainly enhanced by the dynamic range control processing.
[0046]
That is, as can be seen by looking closely at each of the levels L1, L2, L3 and L4 in FIG. 6A, the
level L1 and L2 with high output levels have no change with the input level, and the output
characteristics of the lowest level L4 As for the characteristic of (3), the correction of the
sensitivity β and the loudness correction are performed at the same time, and the characteristic
of drawing a curve in which the sensitivity of the low band and the high band is increased. In the
case of this example, the curve state on the low band side and the curve state on the high band
side are set individually and are not the same. In addition, with regard to level L3 between level
L2 and level L4, only the low range and high range enhanced by the loudness correction are
slightly higher, and as the level becomes higher, the degree of loudness correction becomes
weaker Can be seen. For example, the level L3 shown in FIG. 6A is a level near the abovementioned predetermined level, which is a change point between the range in which the abovedescribed dynamic range control processing is performed and the range in which the input and
output linearly change. Do.
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[0047]
By performing correction in this manner, as input / output characteristics of audio signals output
from the speaker devices 30L and 30R, for example, as shown in FIG. 6B, for levels L1 and L2
having high output levels, There is no change with the input level, and for the output
characteristics of low level L4, only the low and high regions enhanced by the loudness
correction are high, and compared with FIG. 6A, to correct the speaker characteristics. It is
lowered by the increased sensitivity β. As for the level L3, only the low range and high range
enhanced by loudness correction are slightly higher.
[0048]
By performing dynamic range control with such loudness control function, for the large-level
signal component of the audio signal to be reproduced, the overall reproduction balance can be
achieved with almost no change in the reproduction level at any frequency band. With good
condition maintained, only low-frequency and high-frequency signal components lacking in
auditory sense can be enhanced only for low-level signals, and auditory characteristic correction
can be performed well. Moreover, since the poor input / output for the low level signal possessed
by the speaker device is corrected by the dynamic range control correction, as an input / output
characteristic of the overall reproduced audio signal excluding the portion lifted by the loudness
control Is a characteristic with linearity, and can perform very good audio signal reproduction.
[0049]
And since it can set also about dynamic range control which does not make such a loudness
amendment add, a user can choose a desired amendment state, for example, it becomes possible
to choose an amendment state suitable for music to be reproduced. The gain for raising the low
level signal by the loudness correction may be variably set.
[0050]
Note that the reproduction system of this embodiment is applicable to various audio
reproduction systems, and in the example shown in FIG. 1, the audio signal source 10, the
amplifier device 20, and the speaker devices 30L and 30R are separately configured. It may be
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an integrated system (apparatus). Alternatively, a correction means for correcting the
characteristics of the single speaker device may be incorporated in a single speaker device, and
may be connected to an amplifier device having no correction processing function. Alternatively,
the same correction may be applied to the audio signal itself output from the audio signal source
10.
[0051]
Also, for example, the audio reproduction system of this example may be applied to a so-called
reproduction system for car stereos mounted on a vehicle such as a car. By applying to such a
reproduction system for car stereo, for example, in a reproduction environment where the
influence of external noise is large, it becomes easy to hear a small level sound which is generally
easily scraped by noise, and the sound quality is improved. In particular, by combining the
loudness correction as described above, it is possible to clearly hear low-level and high-level lowlevel signals that are particularly difficult to hear, and the clarity of the reproduced sound can be
effectively improved.
[0052]
In the above-described embodiment, as the dynamic range control correction with the loudness
control function, the low band and the high band in the entire reproduction band are performed.
However, for example, the loudness correction is performed only to the low band The loudness
correction may be performed only for the low frequency area by performing correction such that
the middle frequency range and the high frequency range are increased by the sensitivity β
shown in FIG. 6A, for example.
[0053]
Further, although the application to the system for 2-channel audio reproduction shown in FIG. 1
is assumed in the embodiment described above, it may be configured as a system for multichannel audio reproduction such as 5.1 channel.
[0054]
It is a block diagram showing an example of system composition by one embodiment of the
present invention.
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It is a block diagram showing an example of composition by a 1 embodiment of the present
invention.
It is a flowchart which shows the example of a correction process by one embodiment of this
invention. FIG. 6 is a characteristic diagram showing an example of correction characteristics
according to an embodiment of the present invention. It is the characteristic view which showed
the example (example without loudness correction ¦ amendment) of the correction ¦ amendment
state by one embodiment of this invention by the output sensitivity for every frequency. It is the
characteristic view which showed the example (example with loudness correction ¦ amendment)
of the correction ¦ amendment state by one embodiment of this invention by the output
sensitivity for every frequency. It is explanatory drawing which showed the example of an output
waveform of the conventional speaker. It is explanatory drawing which showed the example of
the signal level of the conventional speaker. It is explanatory drawing which showed the output
characteristic example (a) of an ideal speaker, and the output characteristic example (b) of the
conventional speaker. It is explanatory drawing which showed the example of the input-output
characteristic of the conventional speaker. It is a characteristic view showing an example of a
characteristic of conventional loudness correction.
Explanation of sign
[0055]
DESCRIPTION OF SYMBOLS 10 Audio signal source 20 Amplifier device 20a Operation part 21
Audio signal input terminal 24 Amplifier 30L, 30R Speaker device 31 Speaker unit 41 Analog /
digital converter 42 DSP (Digital signal processor) 43: digital / analog converter 44: control unit
45: memory
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