JP2008103880

Patent Translate
Powered by EPO and Google
Notice
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
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2008103880
PROBLEM TO BE SOLVED: To provide an audio apparatus capable of obtaining a low-pitched
sound with suppressed distortion even with a small diameter speaker. SOLUTION: A high pass
filter 2 for extracting a middle high frequency component S2 higher than a resonance frequency
f0 of a speaker 5 from an audio signal S1 and a band for extracting low frequency component
S21 whose frequency is included in a band f0 / 2 to f1 from an audio signal S1. A pass filter 21 is
provided. A pitch shift circuit 22 is provided which doubles the output of the band pass filter 21
and outputs a doubled harmonic component S22. A gain control circuit 23 for dynamically
controlling the level of the harmonic component S22 and a level detection circuit 71 for
detecting the input level of the gain control circuit 23 are provided. An addition circuit 3 is
provided for adding the middle high frequency component S2 and the harmonic component S23
output from the gain control circuit. Dynamic control of the level of the harmonic component
S23 in the gain control circuit 23 is performed by the detection signal S71 of the level detection
circuit 71, and the output signal S3 of the addition circuit 3 is supplied to the speaker 5.
[Selected figure] Figure 1
Audio playback device
[0001]
The present invention relates to an audio reproduction apparatus.
[0002]
In so-called mini components and thin televisions, etc., a speaker with a small aperture is used,
08-05-2019
1
but the volume of an enclosure (speaker box) housing the speaker tends to be small.
For this reason, the resonance frequency f0 of the speaker is increased to about 100 Hz or more.
[0003]
Generally, when an audio signal at a resonance frequency f0 or less is supplied to the speaker,
the output sound pressure of the fundamental wave component gradually decreases as the
frequency decreases, and the distortion component (harmonic component) rapidly increases.
There is a tendency to
[0004]
Therefore, in an audio device using a speaker with a small aperture as described above, bass at a
resonance frequency f0 or less of the speaker can not be reproduced sufficiently.
[0005]
By the way, the sound of an instrument is composed of a fundamental sound and its overtones,
and the ratio determines the timbre.
And, even if the fundamental sound is not output, it is psychoacoustically demonstrated that the
human auditory sense is perceived as if the basic sound is output if the overtone is output.
[0006]
Therefore, an audio device has been considered that can obtain a bass feeling by using such
perceptual characteristics.
FIG. 13 shows an example of such an audio apparatus, in which reference numeral 5 is a speaker
targeted for improvement of the bass feeling.
[0007]
08-05-2019
2
Then, the audio signal S1 is supplied to the high pass filter 2 through the input terminal 1, and as
shown in FIG. 14A, the mid-high band component S2 higher than the resonance frequency f0 of
the speaker 5 is extracted. Supplied to Further, the audio signal S1 at the input terminal 1 is
supplied to the band pass filter 7, and as shown in FIG. 14B, the low frequency component S7
included in the frequency band f0 / 2 to f0 is extracted, and the low frequency component S7 has
a pitch The shift circuit 8 is supplied.
[0008]
The pitch shift circuit 8 doubles the frequency of the low frequency component S7 supplied
thereto, and therefore, as shown in FIG. 14C, the pitch shift circuit 8 has a frequency of f0 to 2f0.
The harmonic wave component S8, that is, the harmonic component S8 is output.
[0009]
Then, the harmonic component S8 is supplied to the addition circuit 3 and added to the middle
high frequency component S2, and the addition circuit 3 generates an audio signal S3 in which
the harmonic component S8 of the low frequency component S7 is enhanced as shown in FIG.
14D. The signal S 3 is taken out and supplied to the speaker 5 through the power amplifier 4.
Therefore, the speaker 5 outputs an acoustic output having a frequency characteristic as shown
in FIG. 14D, that is, an acoustic sound in which the overtone component S8 of the low frequency
component S7 is enhanced.
[0010]
In this case, although the low-frequency component S7 does not output the sound of the lowfrequency component S7 from the speaker 5, the low-frequency component S7 corresponds to
the basic sound component and the sound of the overtone component S8 is output as described
above. The listener is perceived as if the sound of the low-pass component S7 is output, and
therefore, even if the speaker 5 has a small aperture, a low-pitched feeling can be obtained.
[0011]
Generally, when the low-frequency component S7 is subjected to multiplication processing to
generate the overtone component S5, if the frequency of the overtone component S8 is about
08-05-2019
3
200 Hz or less, it is considered that the sense of incongruity is not felt.
[0012]
Examples of prior art documents are as follows.
Unexamined-Japanese-Patent No. 8-213862 gazette
[0013]
However, in the case of the above-described audio reproduction apparatus, the harmonic
component S8 is also a component similar to the harmonic distortion component of the low
frequency component S7.
For this reason, if the harmonic component S8 is increased in order to strengthen the bass
feeling, the distortion feeling becomes strong, and conversely, if the harmonic component S8 is
reduced to weaken the distortion feeling, the bass feeling becomes weak. That is, there is a tradeoff between bass and distortion.
[0014]
The present invention is intended to solve such problems.
[0015]
In the present invention, N = 2 <n> where n is an integer from 1 to 6 f0: resonance frequency of
the speaker f1: when the fundamental wave component of a certain signal is multiplied, the
resulting multiplied wave component makes the sense of hearing discomfort And a high pass
filter for extracting the middle and high frequency components above the resonance frequency
f0 from the audio signal, and a low frequency component whose frequency is included in the
band f0 / N to f1 / N from the audio signal And n pitch shift circuits for multiplying the outputs
of the n band pass filters by N to form N overtone components, and the overtone components
being supplied. A gain control circuit for dynamically controlling the level, a level detection
circuit for detecting an input level of the gain control circuit, and a mid-high band extracted by
the high pass filter The gain control circuit dynamically controls the level of the overtone
08-05-2019
4
component in accordance with the detection output of the level detection circuit in the gain
control circuit. According to another aspect of the present invention, there is provided an audio
reproduction apparatus in which an output signal of the addition circuit is supplied to the
speaker.
[0016]
According to the present invention, when the frequency of the low frequency component of the
audio signal is lower than the resonance frequency f0 of the speaker, the sound of the harmonic
component of the low frequency component is output. You can get
In addition, since the level is dynamically changed when the harmonic component is output, it is
possible to obtain a sharp bass sound and reduce distortion.
[0017]
[1] First Example FIG. 1 shows a first example of the present invention, in which reference
numeral 5 is a speaker with a small aperture, which is an object of improvement in bass.
Here, f 0: resonant frequency of the speaker 5. In this example, around 100 Hz or less. f1: When
the fundamental wave component of a certain signal is multiplied, the frequency of the upper
limit (the frequency of the signal of the multiplication result) that does not cause a sense of
incongruity in the multiplied wave component of the result. Generally around 200 Hz. とする。
In this example, f0 = f1 / 2 (or f0 ≦ f1 / 2). In the case of two-channel stereo or multi-channel
stereo, each channel can be configured as shown in FIG.
[0018]
Then, the audio signal S1 is supplied to the high pass filter 2 through the input terminal 1, and as
shown by the solid line in FIG. 2A, the mid-high band component S2 higher than the resonance
frequency f0 of the speaker 5 is extracted and this mid-high band component S2 is added It is
supplied to the circuit 3. Further, a band pass filter 11 having a pass band of frequencies f0 to f1
(100 Hz to 200 Hz in this example) is provided, and the audio signal S1 from the input terminal
08-05-2019
5
1 is supplied to the band pass filter 11 and a broken line is shown in FIG. As shown, the low band
component S11 having a frequency band of f0 to f1 is extracted, and this low band component
S11 is supplied to the adding circuit 3 through the attenuator circuit 13.
[0019]
Furthermore, a band pass filter 21 is provided with a pass band of frequencies f0 / 2 to f1 / 2, 50
Hz to 100 Hz in this example, and the audio signal S1 from the input terminal 1 is supplied to the
band pass filter 21. As shown in FIG. 2B, a low frequency component S21 having a frequency of
f0 / 2 to f1 / 2 is extracted, and this low frequency component S21 is supplied to the pitch shift
circuit 22.
[0020]
The pitch shift circuit 22 doubles the frequency of the low-frequency component S21 supplied to
the pitch shift circuit 22 as described later, and therefore, as shown in FIG. 2C, the pitch shift
circuit 22 doubles it. The harmonic component S22 having a frequency twice as high, that is, the
harmonic component S22 having a frequency of f0 to f1 is output.
Then, the double harmonic component S22 is supplied to a gain control circuit 23, which will be
described later, to be a level-controlled harmonic component S23, and this harmonic component
S23 is supplied to the addition circuit 3.
[0021]
Thus, as shown in FIG. 2D, the addition circuit 3 extracts the audio signal S3 in which the low
frequency component S11 and the double harmonic component S22 are added to the middle
high frequency component S2 at a predetermined ratio. Then, the addition signal S 3 is supplied
to the speaker 5 through the power amplifier 4.
[0022]
In the present invention, in addition to the above, the following is configured. That is, while the
gain control circuit 23 is provided as described above, the harmonic component S22 output from
08-05-2019
6
the pitch shift circuit 22 is supplied to the level detection circuit 71, and for example, as shown
in FIG. That is, for example, a period Tx from the time when the polarity reverses from negative
to positive to the time when the polarity reverses from negative to positive next is one cycle
period, and the peak level (absolute value) V22 in this one cycle period Tx is detected. The
detection signal S71 is supplied to the gain control circuit 23 as a control signal of its gain.
[0023]
FIG. 4 shows an example of control characteristics of the gain control circuit 23. The horizontal
axis represents the input level of the harmonic component S22 supplied to the gain control
circuit 23, that is, in one cycle period Tx detected by the detection signal S71. The peak level V22
of the harmonic component S22 is shown, and the vertical axis is the output level V23 of the
harmonic component S23 output from the gain control circuit 23. The broken line B shows the
characteristic when the gain is 1 regardless of the peak level V22 (input level), for reference.
[0024]
And VLM: predetermined upper limit value set in advance VTH: predetermined threshold level
set in advance However, when VLM> VTH, the control characteristic of the gain control circuit 23
is represented by the characteristic A of the polygonal line, and V22 ≧ When VLM, limit V23 to
VMAX. When V22 <VLM, the level V23 is linearly proportional to the level V22. When VTH
<V22 <VLM, the gain is greater than 1 ×. When V22 = VTH, the gain is 1 ×. The gain is smaller
than 1 when V22 <VTH. とされている。
[0025]
The overtone component S22 is controlled in level in accordance with the detection signal S71
and the control characteristic A every one cycle period Tx, and is set as the overtone component
S23. Although the peak level V22 in one cycle period Tx can not be known until the one cycle
period Tx ends, in the following, for the sake of simplicity, the one cycle period Tx is started at
the start of one cycle period Tx. It is assumed that the peak level V22 can be detected. In order to
realize such detection and control, the level-controlled overtone component S22 may be delayed
in advance and synchronized with the corresponding detection signal S71.
08-05-2019
7
[0026]
According to such a configuration, when the audio signal S1 is supplied to the input terminal 1,
the pitch shift circuit 22 forms an overtone component S22 which is twice the low frequency
component S21, and the overtone component S22 is gain controlled. The harmonic component
S23 whose level is controlled by the circuit 23 is used as the harmonic component S23, and the
harmonic component S23 and the low frequency component S11 are added to the middle high
frequency component S2 in the addition circuit 3. Therefore, although the audio signal S3 of a
frequency characteristic as shown to FIG. 2D is output from the addition circuit 3, this signal S3
is supplied to the speaker 5, and the sound is output.
[0027]
And in this case, although the sound of the fundamental sound component of the resonance
frequency f0 or less is hardly output from the speaker 5, since the sound of the harmonic
component S22 of the low frequency component S21 (FIG. 2B) is outputted, as described above It
is perceived as if the sound with the resonance frequency f0 or less is output, and therefore, even
if the speaker 5 has a small aperture, a bass feeling can be obtained.
[0028]
Further, since the gain control circuit 23 has a control characteristic as shown in FIG. 4, the
waveform (level) of the outputted overtone component S23 is as shown by a broken line in FIG.
That is, when the peak level V22 of one cycle period Tx in which the harmonic component S22 is
present is smaller than the threshold level VTH, the output level V23 of the harmonic component
S23 is larger than the original level, as shown by arrow C in FIG. It becomes smaller. Further,
when the peak level V22 of one cycle period Tx with the harmonic component S22 is larger than
the threshold level VTH, as indicated by an arrow D in FIG. 4, the output level V23 of the
harmonic component S23 is larger than the original size. Become.
[0029]
Therefore, the level (waveform) V23 of the harmonic component S23 output from the gain
control circuit 23 is smaller in one cycle period Tx when the peak level V22 is smaller than the
08-05-2019
8
threshold level VTH, as shown by the broken line in FIG. Conversely, the peak level V22 becomes
larger in one cycle period Tx in which the peak level V22 is larger than the threshold level VTH.
Thus, since the level of the harmonic component S23 changes dynamically, it is possible to obtain
a sharp bass sound and to suppress distortion.
[0030]
Further, as shown in FIGS. 2A and 2D, the low frequency component S11 included in the original
input audio signal S1 is also enhanced, so that the bass can be made natural.
[0031]
[2] Second Example FIG. 5 shows a second example of the present invention, and in this example,
it is a case where the bass feeling is more effectively obtained.
That is, as shown in FIG. 6A (same as FIG. 2A), the middle high frequency component S2 and the
low frequency component S11 are extracted from the input audio signal S1 and supplied to the
adder circuit 3 as in the device of FIG.
[0032]
Also, the input audio signal S1 is supplied to the band pass filter 21, and as indicated by a broken
line in FIG. 6B, the low frequency component S21 having a frequency of f0 / 2 to f1 / 2 is
extracted, and this low frequency component S21 has a pitch As shown by the solid line in FIG.
6B, it is supplied to the shift circuit 22. As shown by the solid line in FIG. 6B, the overtone
component S22 having a double frequency, ie, the overtone component S22 having a frequency
of f0 to f1 is extracted.
[0033]
Further, the input audio signal S1 is supplied to the band pass filter 41, and as shown by a
broken line in FIG. 6B, the low frequency component S41 having a frequency of f0 / 4 to f1 / 4 is
extracted. As shown by the solid line in FIG. 6B, it is supplied to the shift circuit 42, and as shown
by the solid line in FIG.
[0034]
08-05-2019
9
Then, the harmonic component S22 from the pitch shift circuit 22 and the harmonic component
S42 from the pitch shift circuit 42 are supplied to the addition circuit 24, and the addition circuit
24 has harmonic components S22 and S42 as shown in FIG. 6C. The harmonic component S24 is
extracted.
Then, the harmonic component S24 is supplied to the addition circuit 3 through the gain control
circuit 23, and the addition circuit 3 outputs a low frequency component S11 and a double
harmonic component S22 to the middle high frequency component S2, as shown in FIG. 6D. And
an audio signal S3 in which the quadruple harmonic component S42 is added at a predetermined
ratio.
Then, the addition signal S 3 is supplied to the speaker 5 through the power amplifier 4.
[0035]
Furthermore, in this case, the harmonic component S24 output from the adding circuit 24 is
supplied to the gain control circuit 23, and is also supplied to the level detection circuit 71, and
one cycle period Tx is supplied for each one cycle period Tx of the harmonic component S24. The
peak level V22 at the point V.sub.2 is detected, and the detection signal S71 is supplied to the
gain control circuit 23 as a gain control signal in the one cycle period Tx.
[0036]
Therefore, in this example, since the audio signal S3 of the frequency characteristic as shown in
FIG. 6D is supplied to the speaker 5, the sound of the fundamental sound component of the
resonance frequency f0 or less is hardly output from the speaker 5 Since the sound of the
harmonic component S22 and the quadruple harmonic component S42 is output, it is perceived
as if the listener is outputting a sound having a resonance frequency f0 or less at the listener.
Therefore, even if the speaker 5 has a small aperture, You can get a feeling of bass.
[0037]
The level (waveform) V23 of the harmonic component S23 output from the gain control circuit
23 is smaller in one cycle period Tx in which the peak level V22 is smaller than the threshold
level VTH, as shown by the broken line in FIG. Conversely, the peak level V22 becomes larger in
one cycle period Tx in which the peak level V22 is larger than the threshold level VTH.
08-05-2019
10
[0038]
Therefore, since the level of the harmonic component S23 dynamically changes, it is possible to
obtain a sharp bass sound and to suppress distortion.
[0039]
Furthermore, for example, as shown in FIG. 7A, if the frequency of the low frequency component
S21 (S41) is 35 Hz, even if the harmonic component S22 (shown by a broken line) having a
frequency twice that of the low frequency component S21 is generated, The frequency is 70 Hz
and can not be reproduced by the speaker 5.
[0040]
However, in the apparatus of FIG. 5, if the frequency of the low frequency component S21 (S41)
is 35 Hz, the low frequency component S21, that is, the low frequency component S41 is
supplied to the pitch shift circuit 42 through the band pass filter 41. A harmonic overtone
component S42 (shown by a solid line) having a frequency of 140 Hz which is four times as large
is formed, and this harmonic overtone component S42 is supplied to the addition circuit 24.
Therefore, even if the frequency of the low frequency component S21 (S41) is 35 Hz, it is
possible to obtain a bass feeling corresponding to the low frequency component S21 by the
harmonic component S42 having a frequency four times that of the low frequency component
S21 (S41).
[0041]
For example, as shown in FIG. 7B, if the frequency of the low frequency component S41 (S21) is
60 Hz, then if the harmonic overtone component S42 (indicated by the broken line) having a
frequency four times that of the low frequency component S41 is generated, the frequency is
Since the frequency is 240 Hz and exceeds the upper limit frequency f1 (.apprxeq.200 Hz) at the
time of adding the harmonics, supplying the harmonics component S42 to the speaker 5 results
in an unpleasant sound.
[0042]
However, in the apparatus of FIG. 5, if the frequency of the low frequency component S41 (S21)
08-05-2019
11
is 60 Hz, the low frequency component S41, ie, the low frequency component S21, is supplied to
the pitch shift circuit 22 through the band pass filter 21. The harmonic component S22 (shown
by a solid line) having a frequency of 120 Hz which is twice as high as that of the doubled
component is supplied to the adding circuit 24.
Therefore, even if the frequency of the low frequency component S41 (S21) is 60 Hz, a bass
feeling corresponding to the low frequency component S41 can be obtained by the harmonic
component S22 having a frequency twice as high as that.
[0043]
[3] Third Example FIG. 8 shows a third example of the present invention, in which a low-pitched
feeling can be effectively obtained even if f0> f1 / 2.
That is, as in the apparatus of FIG. 5, the middle high frequency component S 2 and the low
frequency component S 11 are extracted from the input audio signal S 1 and supplied to the
addition circuit 3.
[0044]
Further, as shown in FIG. 9A (same as FIG. 6C), the band-pass filters 21 and 41, the pitch shift
circuits 22 and 42, and the addition circuit 24 as in the apparatus of FIG. , S42 is formed, and the
harmonic component S24 is formed, and the harmonic component S24 is supplied to the low
pass filter 25.
The low pass filter 25 has a frequency characteristic in which the vicinity of the resonance
frequency f0 is a cutoff frequency and the input signal component is substantially blocked at the
upper limit frequency f1, as shown by, for example, a curve F25 in FIG. 9B.
[0045]
Therefore, the low-pass filter 25 outputs the double and quadruple harmonic component S25
08-05-2019
12
(hatched portion) of the harmonic component S24 that does not give a sense of discomfort.
Then, the harmonic component S25 is supplied to the addition circuit 3 through the gain control
circuit 23, and is also supplied to the level detection circuit 71, and the peak level V22 in one
cycle period Tx is provided for each one cycle period Tx of the harmonic component S25. Is
detected, and the detection signal S71 is supplied to the gain control circuit 23 as a control
signal of the gain in the one cycle period Tx.
[0046]
According to such a configuration, the pitch shift circuits 22 and 42 form the harmonic
component S22 or S42 having a frequency twice or four times that of the low frequency
component S21 or S41, as in the apparatus of FIG. As described above, the speaker 5 is perceived
as if a sound having a resonance frequency f 0 or less is output, and therefore, even if the
speaker 5 has a small aperture, it can obtain a bass feeling. it can.
[0047]
Then, in this case, the harmonic component S23 of 2 times and 4 times is added to the middle
high frequency component S2 in the adding circuit 3, but the level of the harmonic component
S23 is reduced by the low pass filter 25 as it approaches the upper limit frequency f1. Therefore,
even if the overtone component S24 contains a signal component exceeding the upper limit
frequency f1, it is not included in the overtone component S23.
As a result, even if f0> f1 / 2, for example, it is possible to obtain a bass feeling without giving a
sense of incongruity.
[0048]
[4] An example of the pitch shift circuits 22 and 42 The overtone components S22 and S42
having a frequency twice or four times the low frequency components S21 and S41 can be
formed, for example, by the method shown in FIG.
That is, as shown in FIG. 10A, it is assumed that digital data DA that can be D / A converted in
08-05-2019
13
one cycle of the sine wave signal SA is stored in the memory. The symbol ● indicates the sample
point. Further, the period TA is one cycle period of the sine wave signal SA, and the period 1 / fc
is one sample period.
[0049]
Then, when the digital data DA is read out from the memory, one cycle of the sine wave signal SA
can be obtained in the period TA by reading out one sample at a time at a clock frequency fc
equal to that at the time of writing.
[0050]
When digital data DA is read out from the memory, as shown in FIG. 10B, it is thinned out and
read at a rate of 1 for every 2 addresses at a clock frequency fc equal to that at the time of
writing. Two cycles of a sine wave signal SB having a frequency twice that of the sine wave signal
SA can be obtained at TA.
That is, the harmonic component SB having a frequency twice that of the sine wave signal SA can
be obtained in the period TA.
[0051]
Furthermore, when reading digital data DA from the memory, as shown in FIG. 10C, while
thinning out and reading at a rate of 1 for every 4 addresses at a clock frequency fc equal to the
time of writing, reading is repeated four times, the period Four cycles of a sine wave signal SC
having a frequency four times that of the sine wave signal SA can be obtained at TA. That is, the
harmonic component SC having a frequency four times that of the sine wave signal SA can be
obtained in the period TA.
[0052]
Therefore, the pitch shift circuit 22 (and 42) can be configured, for example, as shown in FIG.
That is, in FIG. 11, reference numeral 22M denotes a memory circuit which is configured by, for
example, a ring buffer and has an address (capacity) of a substantially sufficient size. Further, it is
08-05-2019
14
assumed that the low-frequency component S21 is, for example, a waveform as shown in FIG.
12A, a signal obtained by A / D converting this is digital data D21, and its sampling frequency
(clock frequency) is fc.
[0053]
Further, a point in time when the polarity of the digital data D21 (low range component S21)
inverts, for example, from negative to positive is taken as time tx. In addition, a period from a
certain time point tx to the next time point tx, that is, one cycle period of the low-frequency
component S21 is a period Tx.
[0054]
Then, in FIG. 11, the digital data D21 is supplied to the memory circuit 22M through the input
terminal 22A, and as shown in FIG. 12A, the digital data D21 is sequentially written in each
address of the memory circuit 22M every one sample. Go. Therefore, the period Tx in FIG. 12
corresponds to the period TA in FIG. 10, and FIG. 12A corresponds to FIG. 10A.
[0055]
At the same time as this writing, digital data D21 written to the memory 22 in the immediately
preceding period Tx is read from the memory 22. In FIG. 12, for the sake of simplicity, the period
Tx on the write side and the period Tx on the read side are assumed to be the same.
[0056]
The reading from the memory 22 is executed in the same manner as in FIG. 10B, that is, it is read
by thinning out at a rate of 1 for every 2 addresses at a clock frequency fc equal to that at the
time of writing. In addition, the reading is repeated twice in the period Tx. Therefore, if the read
out digital data D22 is D / A converted, it is possible to obtain the harmonic component S22
having a frequency twice that of the original low frequency component S21.
08-05-2019
15
[0057]
Furthermore, the low frequency component S41 is also A / D converted and written to the
memory in the same way, and if it is read as in FIG. 10C, that is, the clock frequency fc is equal to
that at the time of writing. If thinning out and reading out are repeated four times in the period
Tx, when the read out digital data is D / A converted, it is possible to obtain the harmonic
component S42 having a frequency four times that of the original low frequency component S41.
.
[0058]
[5] Summary According to the above-described apparatus, even if the frequency of the low
frequency component S21 is lower than the resonance frequency f0 of the speaker 5, the pitch
shift circuit 22 forms the harmonic component S22 of a frequency higher than the resonance
frequency f0 of the speaker 5 Since this is added to the mid-high frequency component S2 and
supplied to the speaker 5, a low-pitched feeling can be obtained even if the diameter of the
speaker 5 is small.
[0059]
Moreover, in this case, since the level of the multiplication component S22 is dynamically
changed according to the level, for example, as shown in FIG. 3, it is possible to obtain sharp bass
with reduced distortion. Can.
[0060]
Furthermore, when the low frequency component S21 is multiplied, since the harmonic
component of the multiplication result falls within the band between the resonance frequency f0
of the speaker 5 and the upper limit frequency f1, it is doubled or quadrupled. There is no sense
of discomfort.
[0061]
Also, for example, the harmonic component of the frequency of 3 times is not in an octave
relation to the original fundamental sound component, and thus gives a sense of discomfort, but
the harmonic component of the frequency of 2 or 4 times is the original basic The frequency
component is higher by one octave or two octaves with respect to the wave component, and the
reproduced sound does not have a sense of discomfort.
[0062]
08-05-2019
16
[6] Others In the above description, the level detection circuit detects the peak level V22 in one
cycle period Tx and controls the gain for the one cycle period Tx, but detects the average level in
one cycle period Tx. The gain for the cycle period Tx can also be controlled.
Alternatively, the level may be detected for each sample of the multiplied component supplied to
the detection circuit 71, that is, the envelope may be detected to control the gain.
At that time, the attack time, the release time, and the like can be set in consideration of the
characteristics of the speaker 5.
[0063]
Furthermore, the control characteristic of the gain control circuit 23 can be reversed from that in
FIG. 4, that is, when V22> VTH, the gain is smaller than one.
When V22 = VTH, the gain is 1 ×.
When V22 <VTH, the gain is greater than 1 ×.
In this case, since it acts like an AGC, a bass feeling can always be obtained.
[0064]
Further, in the above, the signal system for obtaining the output audio signal S3 from the input
audio signal S1 is actually realized by digital processing using a DSP or dedicated hardware, so,
for example, the pitch shift circuit 22 and The memory can be shared with the gain control
circuit 23.
[0065]
Also, in the above description, as shown in FIG. 10, the pitch shift circuit 22 doubles the
frequency of each low frequency component D21 (S21) input in units of one cycle as a unit
(division). It is also possible to multiply by 2 in units of the period of the unit, in which case,
08-05-2019
17
process so that the last part of the waveform of one period and the first part of the waveform of
the next period are connected smoothly. Can.
[0066]
Furthermore, although the frequency f0 is the resonance frequency of the speaker 5 in the above
description, in an actual product, it may be set to another frequency corresponding to the
frequency to obtain a bass feeling.
In addition, since low-frequency components with considerably low frequencies may be recorded
in CDs and SACDs, etc., when bass is to be obtained from these low-frequency components as
well, in addition to the double and quadruple harmonic components. Is an overtone component
such as 8 times, 16 times, 32 times, etc., that is, an overtone component whose frequency does
not exceed the upper limit frequency f1 and N times the low frequency component for which a
low-pitched feeling is desired (N = 2 <n>).
A harmonic component of n = 1 to 6 can be added.
[0067]
[List of Abbreviations] A / D: Analog to Digital AGC: Automatic Gain Control CD: Compact Disc D /
A: Digital to Analog DSP: Digital Signal Processor SACD: Super Audio CD
[0068]
It is a systematic diagram showing one form of this invention.
It is a frequency characteristic figure for demonstrating this invention. It is a wave form diagram
for explaining this invention. It is a control characteristic view for explaining this invention. It is a
systematic diagram which shows the other form of this invention. It is a frequency characteristic
figure for demonstrating the apparatus of FIG. It is a frequency characteristic figure for
demonstrating the apparatus of FIG. It is a systematic diagram which shows the other form of
this invention. It is a frequency characteristic figure for demonstrating the apparatus of FIG. It is
a wave form diagram for explaining this invention. It is a systematic diagram for explaining this
08-05-2019
18
invention. It is a wave form diagram for demonstrating the circuit of FIG. It is a systematic
diagram for explaining this invention. It is a frequency characteristic figure for demonstrating the
circuit of FIG.
Explanation of sign
[0069]
DESCRIPTION OF SYMBOLS 1 ... Input terminal, 2 ... High pass filter, 5 ... Speaker, 11, 21 and 41
... Band pass filter, 22 and 42 ... Pitch shift circuit, 23 ... Gain control circuit, 71 ... Level detection
circuit
08-05-2019
19

Download Report