close

Вход

Забыли?

вход по аккаунту

?

JP2010183126

код для вставкиСкачать
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 JP2010183126
[Object] To reproduce acoustic information lower than the lowest resonance frequency of a
speaker in a natural state in terms of hearing. A low-pass signal S2 of a frequency f2 lower than
the lowest resonance frequency of a speaker to be used is extracted from an input signal S1
supplied from a signal source, a sine wave signal S3 of a frequency f3 and the low-pass signal S2
And a first multiplication unit for obtaining a converted signal S4 of frequency f3 ± f2, and a
converted signal S5 including a component of frequency f3 and a component of frequency f3 ±
2f2 from the low band signal S2 and the converted signal S4. And adding the converted signal S4
and the converted signal S5 to obtain a pseudo low band signal S7 including the component of
the frequency f3 and the component of the frequency f3 ± f2 and the component of the
frequency f3 ± 2f2 And a unit. [Selected figure] Figure 1
Sound reproduction apparatus and sound reproduction system
[0001]
The present invention relates to an audio reproduction apparatus and an audio reproduction
system, and more particularly to an audio reproduction apparatus and an audio reproduction
system capable of reproducing audio information below the lowest resonance frequency of a
speaker.
[0002]
In recent years, advances in mobile telephone devices and portable digital playback devices are
remarkable.
08-05-2019
1
These devices are used not only to play music, but also to play movies such as movies and TV
shows.
[0003]
A speaker with a diameter of 20 mm or less may be used as a speaker built into this type of
portable device, due to restrictions on the mounting location or the mounting position or the
design. The minimum resonance frequency of such a small-aperture speaker is about 500 Hz to 1
kHz due to the restriction of the vibration area and the structure. Therefore, it is not possible to
reproduce low frequency signals (bass) around 100 Hz.
[0004]
In order to reproduce the bass part included in music using such small-aperture speakers, it is
generally common to emphasize the low-pass part using a loudness compensation circuit or a
tone control circuit. It has been done.
[0005]
However, simply emphasizing the low band part in this way, it is necessary to reproduce a high
amplitude low band signal exceeding the capability of the small aperture speaker, which causes a
problem of increased distortion.
Therefore, there is a method of representing a bass feeling by creating a harmonic component of
this low frequency signal instead of the low frequency signal as it is, and reproducing this
harmonic signal. It is proposed by patent document 2 grade | etc.,.
[0006]
In the method of Patent Document 1, a low frequency signal is multiplied to generate a harmonic
signal of a frequency of squared frequency. Moreover, the method of patent document 2
produces | generates the signal of the double frequency by full-wave rectification of a low-pass
08-05-2019
2
signal.
[0007]
In addition to this, when listening to two signals at the same time, it is a psychoacoustic
phenomenon in which the frequency difference (beat) is felt as a bass, or a basic sound that does
not exist when listening to a plurality of signals of equally spaced frequencies. There is a
psychoacoustic phenomenon known as the missing fundamental that feels like.
[0008]
JP, 2001-245339, A JP, 5-328481, A
[0009]
In the method of emphasizing the low band part using the above loudness compensation circuit
and tone control circuit, the signal below the minimum resonance frequency of the speaker is
amplified, which has limited amplification degree and it is difficult to obtain sufficient bass
volume feeling. In such a case, there is a problem that distortion increases and the sound
becomes unnatural.
[0010]
When the various processes described in Patent Documents 1 and 2 described above are
executed as digital processes, hardware such as a DSP that can perform product-sum operations
at high speed is used.
When an audio signal is processed by an arithmetic system such as a DSP, the input signal is
quantized by the number of quantization bits of the arithmetic system.
For example, when processing an input signal in the range of -1 V to +1 V with a quantization bit
number of 16 bits, the input signal in the range of -1 V to +1 V is associated with a numerical
value in the range of -32768 to +32767 It is processed.
[0011]
In the actual processing inside the DSP, when multiplication is performed using the value in the
08-05-2019
3
range of -32768 to +32767, the calculation system overflows the digit immediately because the
range of values that can be processed by the operation system is in the range of -32768 to
+32767. There is a problem that can not be done.
[0012]
Therefore, calculation is performed by associating the range of -32768 to +32767 with the value
of -1 to +1 inside the DSP, so that the calculation result does not exceed the range of -1 to +1,
regardless of how many multiplications are repeated. Overflow will not occur.
Therefore, this method is generally used when performing multiplication with a DSP or the like.
[0013]
Here, in the case of realizing the method of Patent Document 1 described above using digital
signal processing, assuming that the low band signal is cubed to obtain the third harmonic, the
relationship between the input and output of the multiplier is , It becomes like the formula shown
below.
[0014]
[0015]
The input and output of the mathematical expression by the above trigonometric function
calculation is illustrated as shown in FIG. 13. When the input signal becomes smaller, the level of
the output signal becomes extremely small because it is cubed, and the SN ratio is not good
become.
[0016]
In this case, although it is necessary to amplify the third harmonic obtained at the output of the
multiplier in order to obtain a low-pass signal of a necessary level, there is a problem that noise
is also amplified at that time. Do.
[0017]
Further, in the methods described in Patent Documents 1 and 2 described above, low frequency
08-05-2019
4
signals are multiplied to generate a second harmonic and a third harmonic, and a 100 Hz bass is
reduced to 200 Hz and 300 Hz low frequencies. It simulates in a signal.
[0018]
Therefore, in a device using a small diameter speaker with a minimum resonance frequency of
about 500 Hz to 1 kHz, it is necessary to generate fifth to tenth harmonics having a frequency
higher than the minimum resonance frequency from a low frequency signal of 100 Hz. .
In this case, due to the above-described noise problem in the signal generation process, noise is
further increased and a practical signal can not be obtained, so the low frequency signal to be
reproduced and the reproducible frequency band are separated. If this is the case, it will be
impossible to reproduce by harmonics.
[0019]
On the other hand, the perceptual level at each frequency is known to change depending on the
sound pressure (volume), and is known as an equal sensitivity curve (Robinson-Dadson curve)
shown in FIG.
It can be seen from this figure that the lower the sound pressure, the harder it is to feel the lower
bass.
Therefore, when the low frequency signal of 100 Hz is multiplied to generate the low frequency
signal of 200 Hz, the signal level of the harmonics changes between when the sound pressure is
large (high volume) and when the sound pressure is low (small volume) It means that you need to
let it go.
[0020]
However, none of the above-mentioned patent documents and other documents have attempted
to realize bass reproduction in consideration of the Robinson-Daddson curve.
08-05-2019
5
That is, with the various conventional methods, it was difficult to reproduce natural bass in terms
of hearing.
[0021]
The present invention has been made to solve the problems as described above, and provides an
audio reproduction apparatus and an audio reproduction system capable of reproducing audio
information lower than the lowest resonance frequency of a speaker in a naturally audible state.
The purpose is
[0022]
The present invention for solving the above problems is as described below.
(1) The invention according to claim 1 comprises a filter unit for extracting a low frequency
signal S2 of frequency f2 lower than the lowest resonance frequency of a speaker to be used
from an input signal S1 supplied from a signal source, and a sine wave signal of frequency f3. A
first multiplication unit for obtaining a converted signal S4 of frequency f3 ± f2 from S3 and the
low band signal S2, and a component of frequency f3 and a component of frequency f3 ± 2 f2
from the low band signal S2 and the converted signal S4 And the converted signal S4 and the
converted signal S5 are added, and a component including the component of the frequency f3
and the component of the frequency f3 ± f2 and the component of the frequency f3 ± 2 f2 is
added. This sound reproduction apparatus is characterized by including an addition unit to be
obtained as the low band signal S7.
[0023]
(2) According to the second aspect of the present invention, there is provided a filter section for
extracting a low frequency signal S2 of frequency f2 lower than the lowest resonance frequency
of a speaker to be used from an input signal S1 supplied from a signal source, and a sine wave
signal of frequency f3. A first multiplication unit for obtaining a converted signal S4 of frequency
f3 ± f2 from S3 and the low band signal S2, and a component of frequency f3 and a component
of frequency f3 ± 2 f2 from the low band signal S2 and the converted signal S4 And the
converted signal S4 and the converted signal S5 are added, and a component including the
component of the frequency f3 and the component of the frequency f3 ± f2 and the component
of the frequency f3 ± 2 f2 is added. An adding unit for adding a low-pass signal S7 to the input
08-05-2019
6
signal S1 to obtain a pseudo low-pass signal containing output signal S8, and an amplifying unit
for amplifying the pseudo low-pass signal containing signal S8 to drive the speaker With That is
a sound reproduction device.
[0024]
(3) In the invention according to claim 3, the frequency f3 of the sine wave signal S3 is not less
than twice and not more than 12 times the upper limit frequency f2max passing through the
filter section, and can be reproduced in the frequency band reproducible by the speaker. It is set,
It is a sound reproduction apparatus of Claim 1 or Claim 2 characterized by the abovementioned.
[0025]
(4) In the invention according to claim 4, the first multiplication unit and the second
multiplication unit are digital processing units that execute digital processing, normalize an input
signal within a range of ± 1, and perform multiplication processing It is the sound reproduction
apparatus according to any one of claims 1 to 3, characterized in that frequency conversion is
performed.
[0026]
(5) According to the fifth aspect of the present invention, there is provided a filter section for
extracting a low frequency signal S2 of frequency f2 lower than the lowest resonance frequency
of a speaker to be used from an input signal S1 supplied from a signal source, and a sine wave
signal of frequency f3. A first multiplication unit for obtaining a converted signal S4 of frequency
f3 ± f2 from S3 and the low band signal S2, and a component of frequency f3 and a component
of frequency f3 ± 2 f2 from the low band signal S2 and the converted signal S4 And the
converted signal S4 and the converted signal S5 are added, and a component including the
component of the frequency f3 and the component of the frequency f3 ± f2 and the component
of the frequency f3 ± 2 f2 is added. Acoustic reproduction of an addition unit to be obtained as
the low band signal S7, the input signal S1 and the pseudo low band signal S7, or a pseudo low
band signal-containing output signal S8 obtained by adding the input signal S1 and the pseudo
low band signal S7 A sound reproduction system, characterized in that it includes a transmission
unit to be transmitted to the location.
[0027]
(6) In the invention according to claim 6, the frequency f3 of the sine wave signal S3 is not less
than twice and not more than 12 times the upper limit frequency f2max passing through the
filter section, and can be reproduced in the frequency band reproducible by the speaker. It is a
08-05-2019
7
setting, It is a sound reproduction system of Claim 5 characterized by the above-mentioned.
[0028]
(7) In the invention according to claim 7, the first multiplication unit and the second
multiplication unit are digital processing units that execute digital processing, normalize an input
signal within a range of ± 1, and perform multiplication processing 7. A sound reproduction
system according to claim 5, wherein frequency conversion is performed.
[0029]
(8) In the above (3) and (6), the frequency f3 of the sine wave signal S3 is not less than twice and
not more than 12 times the upper limit frequency f2max passing through the filter section, It is
desirable that it is set to a reproducible frequency band.
[0030]
(9) In the above apparatus or system, it is desirable to provide a sine wave signal source that
generates a sine wave signal of a predetermined frequency.
[0031]
According to the present invention, the following effects can be obtained.
(1) In the invention of the sound reproduction apparatus according to the first aspect, the lowpass signal S2 of the frequency f2 lower than the lowest resonance frequency of the speaker to
be used is extracted by the filter unit from the input signal S1 supplied from the signal source.
The converted signal S4 of frequency f3 ± f2 is generated by the first multiplication unit from
the sine wave signal S3 and the low band signal S2, and the component of frequency f3 and the
frequency f3 ± 2 f2 are generated from the low band signal S2 and the converted signal S4. And
the converted signal S5 is added by adding the converted signal S4 and the converted signal S5
to include the component of the frequency f3 and the component of the frequency f3 ± f2 and
the component of the frequency f3 ± 2f2 The pseudo low band signal S7 is generated by the
adder.
[0032]
As a result, the low frequency signal S2 of frequency f2 lower than the lowest resonance
08-05-2019
8
frequency of the speaker to be used has a frequency interval f2 (± f2, ± 2 f2) centered on the
frequency f3 of the sine wave signal S3 in the reproducible frequency band of the speaker Each
frequency conversion is performed to a pseudo low band signal S7 including a signal component.
[0033]
As a result, the basic sound f2 can be felt by the listener due to the missing fundamental from the
pseudo low band signal S7 including the signals at equal intervals at the center frequency f3 and
the frequency interval f2 in the reproducible frequency band of the speaker.
[0034]
For this reason, the phenomenon that distortion increases when simply emphasizing the low
band portion with the frequency does not occur.
In addition, even when the low frequency signal to be reproduced is separated from the
reproducible frequency band, the low frequency signal can be reproduced without difficulty
unlike the case where the low frequency signal harmonics are generated by multiplication.
become.
Therefore, acoustic information lower than the lowest resonance frequency of the speaker can be
reproduced naturally in a state of hearing.
[0035]
Also, due to the equal sensitivity curve of the Robinson-Daddson curve, several dB to several tens
of dB are easily perceived even if the middle range is reproduced with the same sound pressure
than the low range, so the sound pressure is lower than the actual low range. The low power
consumption of the device can be reduced because the low frequency signal is sufficiently
perceived even when reproduced.
[0036]
(2) In the invention of the sound reproducing apparatus according to the second aspect, the low
frequency signal S2 of the frequency f2 lower than the lowest resonance frequency of the
speaker to be used is extracted by the filter unit from the input signal S1 supplied from the signal
08-05-2019
9
source. The converted signal S4 of frequency f3 ± f2 is generated by the first multiplication unit
from the sine wave signal S3 and the low band signal S2, and the component of frequency f3 and
the frequency f3 ± 2 f2 are generated from the low band signal S2 and the converted signal S4.
And the converted signal S5 is added by adding the converted signal S4 and the converted signal
S5 to include the component of the frequency f3 and the component of the frequency f3 ± f2
and the component of the frequency f3 ± 2f2 The pseudo low band signal S7 is generated and
the pseudo low band signal S7 and the input signal S1 are added to generate the pseudo low
band signal containing output signal S8 by the addition section, and the pseudo low band signal
containing signal S8 is amplified by the amplification section. Increase To drive the speaker was.
[0037]
As a result, the low frequency signal S2 of frequency f2 lower than the lowest resonance
frequency of the speaker to be used has a frequency interval f2 (± f2, ± 2 f2) centered on the
frequency f3 of the sine wave signal S3 in the reproducible frequency band of the speaker Each
frequency conversion is performed to a pseudo low band signal S7 including a signal component.
Then, the pseudo low band signal containing signal S8 including the pseudo low band signal S7 is
reproduced by the speaker.
[0038]
As a result, the basic sound f2 can be felt by the listener due to the missing fundamental from the
pseudo low band signal S7 including the signals at equal intervals at the center frequency f3 and
the frequency interval f2 in the reproducible frequency band of the speaker.
[0039]
For this reason, the phenomenon that distortion increases when simply emphasizing the low
band portion with the frequency does not occur.
In addition, even when the low frequency signal to be reproduced is separated from the
reproducible frequency band, the low frequency signal can be reproduced without difficulty
unlike the case where the low frequency signal harmonics are generated by multiplication.
08-05-2019
10
become.
Therefore, acoustic information lower than the lowest resonance frequency of the speaker can be
reproduced naturally in a state of hearing.
[0040]
Also, due to the equal sensitivity curve of the Robinson-Daddson curve, several dB to several tens
of dB are easily perceived even if the middle range is reproduced with the same sound pressure
than the low range, so the sound pressure is lower than the actual low range. The low power
consumption of the device can be reduced because the low frequency signal is sufficiently
perceived even when reproduced.
[0041]
(3) In the invention of the sound reproduction device according to claim 3, the frequency f3 of
the sine wave signal S3 is not less than twice and not more than 12 times the upper limit
frequency f2max passing through the filter portion, and can be reproduced by the speaker
Because the band is set, the low frequency signal S2 of frequency f2 below the lowest resonance
frequency of the speaker to be used has a frequency interval centered on the frequency f3 of the
sine wave signal S3 within the reproducible frequency band of the speaker The frequency is
converted to a pseudo low band signal S7 including signal components every f2 (± f2, ± 2f2).
Therefore, acoustic information lower than the lowest resonance frequency of the speaker can be
reproduced naturally in a state of hearing.
[0042]
(4) In the invention of the sound reproduction apparatus according to claim 4, the first multiplier
and the second multiplier perform frequency conversion by normalizing the input signal within a
range of ± 1 and performing digital multiplication processing. Since the multiplication process
includes the sine wave signal S3 having a constant signal level, the input and output signal levels
are stabilized as compared with the conventional case where the multiplication process is
performed by the low band signal itself.
08-05-2019
11
As a result, a good low frequency signal can be obtained without deterioration of the SN ratio, so
that acoustic information below the lowest resonance frequency of the speaker can be
reproduced in a natural state in terms of hearing.
[0043]
(5) In the invention of the sound reproduction system according to claim 5, the low-pass signal
S2 of frequency f2 lower than the lowest resonance frequency of the speaker to be used is
extracted by the filter unit from the input signal S1 supplied from the signal source. The
converted signal S4 of frequency f3 ± f2 is generated by the first multiplication unit from the
sine wave signal S3 and the low band signal S2, and the component of frequency f3 and the
frequency f3 ± 2 f2 are generated from the low band signal S2 and the converted signal S4. And
the converted signal S5 is added by adding the converted signal S4 and the converted signal S5
to include the component of the frequency f3 and the component of the frequency f3 ± f2 and
the component of the frequency f3 ± 2f2 The pseudo low band signal S7 is generated by the
adder, and the pseudo low band signal S7 or the pseudo low band signal containing signal S8 is
transmitted by the transmitter to the sound reproduction apparatus.
[0044]
As a result, the low-frequency signal S2 of the frequency f2 lower than the lowest resonance
frequency of the speaker used in the sound reproducing device has a frequency interval f2 (± 2)
around the frequency f3 of the sine wave signal S3 in the reproducible frequency band of the
speaker. The frequency is converted to a pseudo low band signal S7 including a signal
component every f2, ± 2 f2).
[0045]
As a result, the basic sound f2 can be felt by the listener due to the missing fundamental from the
pseudo low band signal S7 including the signals at equal intervals at the center frequency f3 and
the frequency interval f2 in the reproducible frequency band of the speaker.
[0046]
For this reason, the phenomenon that distortion increases when simply emphasizing the low
band portion with the frequency does not occur.
08-05-2019
12
In addition, even when the low frequency signal to be reproduced is separated from the
reproducible frequency band, the low frequency signal can be reproduced without difficulty
unlike the case where the low frequency signal harmonics are generated by multiplication.
become.
Therefore, acoustic information lower than the lowest resonance frequency of the speaker of the
audio reproduction apparatus can be reproduced in a natural state in terms of hearing.
[0047]
Also, due to the equal sensitivity curve of the Robinson-Daddson curve, several dB to several tens
of dB are easily perceived even if the middle range is reproduced with the same sound pressure
than the low range, so the sound pressure is lower than the actual low range. It is possible to
reduce the power consumption of the system because the reproduction of the low band signal is
sufficiently perceived.
[0048]
(6) In the invention of the sound reproduction system according to claim 6, the frequency f3 of
the sine wave signal S3 is not less than twice and not more than 12 times the upper limit
frequency f2max passing through the filter section, and can be reproduced by the speaker Since
the band is set, the low frequency signal S2 of the frequency f2 lower than the lowest resonance
frequency of the speaker used in the sound reproducing apparatus is the frequency f3 of the sine
wave signal S3 within the reproducible frequency band of the speaker. Is frequency-converted to
a pseudo low band signal S7 including signal components at every frequency interval f2 (. +-. F2,.
+-. 2 f2).
Therefore, acoustic information lower than the lowest resonance frequency of the speaker can be
reproduced naturally in a state of hearing.
[0049]
(7) In the invention of the sound reproduction system according to claim 7, the first multiplier
and the second multiplier perform frequency conversion by normalizing the input signal within a
range of ± 1 and performing digital multiplication processing. Since the multiplication process
08-05-2019
13
includes the sine wave signal S3 having a constant signal level, the input and output signal levels
are stabilized as compared with the conventional case where the multiplication process is
performed by the low band signal itself.
As a result, a good low frequency signal can be obtained without deterioration of the SN ratio, so
that acoustic information below the lowest resonance frequency of the speaker can be
reproduced in a natural state in terms of hearing.
[0050]
It is a block diagram which shows the structure of the sound reproduction apparatus of 1st
embodiment of this invention.
It is a block diagram which shows the structure of the sound reproduction apparatus of 1st
embodiment of this invention.
It is a characteristic view which shows the characteristic of the sound reproduction apparatus of
1st embodiment of this invention.
It is a characteristic view which shows the characteristic of the sound reproduction apparatus of
1st embodiment of this invention.
It is a characteristic view which shows the characteristic of the sound reproduction apparatus of
1st embodiment of this invention.
It is a characteristic view which shows the characteristic of the sound reproduction apparatus of
1st embodiment of this invention.
It is a block diagram which shows the structure of the sound reproduction apparatus of 2nd
embodiment of this invention.
08-05-2019
14
It is a block diagram which shows the structure of the sound reproduction apparatus of 3rd
embodiment of this invention.
It is a block diagram which shows the structure of the sound reproduction apparatus of 4th
embodiment of this invention. It is a block diagram which shows the structure of the sound
reproduction apparatus of 5th embodiment of this invention. It is a block diagram which shows
the structure of the sound reproduction apparatus of 6th embodiment of this invention. It is a
characteristic view showing the characteristic of sound reproduction. It is a characteristic view
showing the characteristic of conventional sound reproduction. FIG. 6 is a characteristic diagram
showing the auditory iso-sensitive characteristic of sound reproduction.
[0051]
Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an
embodiment) will be described in detail with reference to the drawings. First Embodiment FIG. 1
is an explanatory view schematically showing a configuration of a sound reproducing apparatus
100 according to a first embodiment of the present invention.
[0052]
Here, the signals S1 to S8 are assigned to the respective signals, and the frequencies of the
respective signals S1 to S8 are f1 to f8. The filter unit 110 is configured of a low pass filter (LPF)
or a band pass filter (BPF), and is supplied with a low frequency signal S2 of a frequency f2 lower
than the lowest resonance frequency of the speaker used from a signal source (not shown) It
extracts from input signal S1 (frequency f1).
[0053]
The sine wave signal source 120 generates a sine wave signal S3 (frequency f3), and supplies the
sine wave signal S3 to the first multiplication unit 130 described later. When the sound
reproducing apparatus 100 is realized by digital signal processing, there are a method of
generating a sine wave, a method of using an IIR filter, and a method of approximating a sine
wave with a polynomial and sequentially calculating. As a simpler method, there is a method in
which a value of a sine wave calculated in advance is stored in a memory and read out, and there
08-05-2019
15
is also an advantage that calculation time can be shortened and a slow DSP can be used.
[0054]
In the above configuration, the frequency f3 of the sine wave signal S3 is twice or more and 12
times or less the upper limit frequency f2max passing through the filter unit 110 or the cutoff
frequency fLPF, and the frequency band reproducible by the speaker 190 It is desirable that it is
set to. By selecting f3 in this range, it is possible to reproduce acoustic information below the
lowest resonance frequency of the speaker in a natural state in terms of hearing.
[0055]
The first multiplication unit 130 uses, for example, multiplication of the conversion signal S4 of
frequency f4 = f3 ± f2 from the sine wave signal S3 of frequency f3 and the low frequency
signal S2 of frequency f2 output from the filter unit 110. Obtained by frequency conversion.
When the first multiplication unit 130 is realized by digital signal processing, a multiplier can be
used.
[0056]
In addition, when the first multiplication unit 130 is a digital processing unit that executes digital
processing, frequency conversion is performed by normalizing an input signal from one of the
input terminals into a range of ± 1, and performing multiplication processing. It is desirable to
do.
[0057]
The second multiplication unit 140 generates the frequency f3 from the low-frequency signal S2
of the frequency f2 output from the filter unit 110 and the conversion signal S4 of the frequency
f4 = f3 ± f2 generated by the frequency conversion of the first multiplication unit 130. The
converted signal S5 of the frequency f5 including the component of f and the component of the
frequency f3 ± 2 f2 is obtained by frequency conversion using multiplication or the like.
The second multiplier 140 can use a multiplier when it is realized by digital signal processing.
08-05-2019
16
[0058]
In addition, when the second multiplication unit 140 is a digital processing unit that executes
digital processing, frequency conversion is performed by normalizing an input signal from one of
the input terminals into a range of ± 1, and performing multiplication processing. It is desirable
to do.
[0059]
The filter unit 150 is configured of a high pass filter (HPF) or a direct current cut filter, and the
signal processing of the above frequency conversion includes a signal whose frequency is 0 Hz
(direct current component) in the converted signal S5. It is a filter which removes a direct current
component and generates conversion signal S6 (conversion signal which removed a direct
current component from conversion signal S5).
[0060]
Here, since the upper limit frequency passing through the filter unit 110 is f2max (or fLPF), and
f4 = f3 ± f2, f5 = (f3, f3 ± 2f2), the lowest frequency f5min after frequency conversion is f5min
= f3-2f2max.
[0061]
Here, if the frequency f3 is the upper limit frequency f2max passing through the filter unit 110
or twice the cutoff frequency fLPF, then f5 min = 0, and a DC component is generated, so the
filter unit 150 described above is necessary. become.
[0062]
As described above, in the case of f3 = 2f2max, that is, f3 = 2f2LPF, it is desirable to set the
cutoff frequency fHPF of the filter unit 150 configured by the high pass filter as fHPF ≦ fLPF to
remove the DC component.
[0063]
In the case where the entire circuit of the sound reproducing apparatus is configured not to
output a direct current component or an ultra low band signal, or when the above frequency f3 is
set larger than f2max or fLPF and the direct current component is not generated. Alternatively,
the filter unit 150 can be omitted.
08-05-2019
17
[0064]
The addition unit 180 adds the converted signal S4 and the converted signal S6 (the converted
signal S5 when the filter unit 150 is not used), and includes the component of the frequency f3,
the component of the frequency f3 ± f2, and the component of the frequency f3 ± 2f2. A
pseudo low band signal (S7) is generated, and the pseudo low band signal (S7) and the input
signal S1 are added to generate a pseudo low band signal containing output signal S8.
[0065]
Although FIG. 1 shows a configuration in which S1, S4 and S6 are added at one time by adding
section 180, as shown in FIG. 2 described later, S4 and S6 are added to add pseudo low band
signal S7. After generation, the pseudo low band signal-containing output signal S8 may be
generated by adding the input signal S1 to the pseudo low band signal S7.
[0066]
The amplification unit 180 is a low frequency amplification unit (audio amplifier) that amplifies
the pseudo low band signal-containing output signal S8.
The speaker 190 is an electronic acoustic conversion element driven by the pseudo low band
signal-containing signal S8 amplified by the amplification unit 180 and performing acoustic
reproduction.
The speaker 190 has a characteristic that the frequency f2 exists below the lowest resonance
frequency because the low frequency signal is reproduced by the pseudo low frequency signal
frequency-converted as described above.
[0067]
That is, the speaker 190 is a speaker of various small diameters which can not reproduce the low
frequency signal S2 to be reproduced due to the restriction of the vibration area and the
structure due to the relation of the minimum resonance frequency.
08-05-2019
18
Alternatively, the speaker 190 is not limited to the small-aperture one, and various types of
speakers that can not reproduce the low-frequency signal S2 of the deep bass to be reproduced
due to the restriction of the vibration area and the various structures including the enclosure. It
is.
[0068]
A pseudo low-pass signal including the component of frequency f3, the component of frequency
f3 ± f2 and the component of frequency f3 ± 2f2 by adding conversion signal S4 and
conversion signal S6 (conversion signal S5 when filter unit 150 is not used) And the pseudo low
band signal and the input signal S1 to generate a pseudo low band signal-containing output
signal S8.
[0069]
The sound reproducing apparatus 100 shown in FIG. 1 described above converts the frequency
of the low frequency signal S2 to generate a pseudo low frequency signal of a frequency band
reproducible by the speaker 190, and generates the pseudo low frequency signal and the input
signal S1. The sound is reproduced from the speaker 190 by the addition and the pseudo low
band signal-containing output signal S8.
[0070]
On the other hand, in the sound reproducing apparatus 100 of FIG. 2, the low band signal S2 is
frequency converted to generate the pseudo low band signal 7 of the frequency band
reproducible by the speaker 190, and the sound reproduction from the speaker 190 is
performed only by the pseudo bass signal S7. Configuration.
That is, it is a kind of subwoofer that acoustically reproduces the low band signal S2 that can not
be reproduced originally as a pseudo low band signal.
[0071]
Here, the relationship of the frequencies when the frequencies of the above-described respective
signals S1 to S8 are f1 to f8 are as shown in FIG.
08-05-2019
19
Here, for the pseudo low band signal S7, f7 = f3 ± (0,1,2) f2 = f3-2 f2, f2-f2, f3, f2 + f2, f3 + 2 f2.
[0072]
That is, the low frequency signal S2 of the frequency f2 lower than the lowest resonance
frequency of the speaker 190 to be used is centered on the frequency f3 of the sine wave signal
S3 in the reproducible frequency band of the speaker. The frequency is converted to a pseudo
low band signal S7 including signal components at every frequency interval f2 (± f2, ± 2f2).
[0073]
As a result, the basic sound f2 can be felt by the listener from the pseudo low band signal S7 in
which the signals at equal intervals are included at the center frequency f3 and the frequency
interval f2 in the reproducible frequency band of the speaker 190 (perceivable ) Would be.
That is, it is perceived by the listener as if there is a signal S2 of frequency f2 which is below the
lowest resonance frequency of the speaker 190 and which is not actually reproduced.
[0074]
For this reason, the phenomenon that distortion at the time of reproduction with the speaker 190
increases when the low band portion is simply emphasized with the frequency as it is does not
occur.
In addition, even when the low frequency signal to be reproduced is separated from the
reproducible frequency band, the low frequency signal can be reproduced without difficulty
unlike the case where the low frequency signal harmonics are generated by multiplication.
become.
Therefore, acoustic information lower than the lowest resonance frequency of the speaker can be
reproduced naturally in a state of hearing.
08-05-2019
20
[0075]
The amplitude level of each component of the pseudo low band signal S7 as described above is
calculated as follows.
First, the conversion signal S4 is expressed by the following equation.
[0076]
[0077]
Further, the conversion signal S5 is expressed by the following equation.
[0078]
[0079]
As a result, the amplitude B of the sine wave signal S3 is constant, and the amplitude A of the low
band signal S2 changes. Therefore, the conversion signal S4 (frequency f4 = f3 ± f2) is
proportional to A / 2. It will be.
Therefore, as shown in FIG. 4, the level of the converted signal S4 is -6 dB of the low band signal
S2.
[0080]
Further, since the amplitude B of the sine wave signal S3 is constant and the amplitude A of the
low band signal S2 changes, the f3 ± 2f2 included in the converted signal S5 is set to (1/1 as
shown in FIG. 4) It will be proportional to A <2>.
08-05-2019
21
Similarly, the sine wave signal S3 included in the pseudo low band signal S7 is proportional to
(1/2) A <2> as shown in FIG.
[0081]
Therefore, when the level (low axis in FIG. 4) of the low band signal S2 is sufficiently large, each
component (S4 (f4) and S5 (f5)) included in the pseudo low band signal S7 as shown in FIG.
Becomes close to the level, so that the interval between the components becomes f2, and the
listener perceives that the low-frequency signal S2 of the frequency f2 is present.
[0082]
On the other hand, when the level of the low band signal S2 (horizontal axis in FIG. 4) is
sufficiently small, as shown in FIG. 6, S5 of the components included in the pseudo low band
signal S7 is significantly smaller than S4. As the level becomes, the interval of the main
component becomes 2 f 2 and the harmonic component of twice the low-pass signal S 2 mainly
exists and the fundamental wave component of the low-pass signal S 2 is faintly present As
perceived by the listener.
[0083]
Since the changes in FIG. 5 and FIG. 6 change as shown in FIG. 4 according to the above
equation, the perceived low band state also gradually changes according to the level of the low
band signal S2.
This change is close to the above-mentioned equal sensitivity curve (Robinson-Dadson curve),
and the perception level at each frequency is changed by the sound pressure (volume).
[0084]
Second Embodiment FIG. 7 is an explanatory view schematically showing a configuration of a
sound reproducing apparatus 100 according to a second embodiment of the present invention.
Here, the same components as those in FIG. 1 of the first embodiment are denoted by the same
reference numerals, and duplicate descriptions will be omitted.
08-05-2019
22
[0085]
In the second embodiment, a state is shown in which the sound reproducing apparatus 100
according to the first embodiment described above is configured to be compatible with stereo
reproduction.
Since the sine wave signal S3 can be used in common, the sine wave signal source 120 is used in
common.
The other circuit units have two channels using the same configuration on the left (L) and the
right (R).
[0086]
In this case, since the low bass signal S2 is independently processed in each channel to generate
the pseudo bass signals S7L and S7R, it is possible to maintain the spread feeling and the sound
image localization in the excellent state even in the low band reproduction. become.
[0087]
Even in the case of a multi-channel having a larger number of channels, it is possible to use the
sine wave signal S3 in common.
Third Embodiment FIG. 8 is an explanatory view schematically showing a configuration of a
sound reproducing apparatus 100 according to a third embodiment of the present invention.
Here, the same components as those in FIG. 1 of the first embodiment and FIG. 7 of the second
embodiment are denoted by the same reference numerals, and duplicate explanations are
omitted.
[0088]
08-05-2019
23
In the third embodiment, a state is shown in which the stereo-compatible 2ch sound reproducing
apparatus 100 of the second embodiment described above is adapted to surround sound. Since
the sine wave signal S3 can be used in common, the sine wave signal source 120 is used in
common. The other circuit units have two channels using the same configuration on the left (L)
and the right (R).
[0089]
Then, the surround processing is applied to the pseudo low band signal containing signal S8L
and the pseudo low band signal contained signal S8R by the surround circuit 101, and then
amplified by the amplifiers 180L and 180R, respectively, and sound reproduction is performed
by the speakers 190L and 190R.
[0090]
Also in this case, since the low-frequency signal S2 is processed independently in each channel to
generate the pseudo low tone signals S7L and S7R, it is possible to maintain the spread feeling
and the sound image localization in an excellent state even in the low-frequency reproduction. It
will be possible.
[0091]
In addition, since surround processing is performed using pseudo bass signals S7L and S7R
generated by processing independently in each channel, surround while maintaining a sense of
spread and sound image localization even in low-pass reproduction. It is possible to generate an
effect.
[0092]
In addition, even in the case of a multi-channel having a larger number of channels, it is possible
to use the sine wave signal S3 in common and to execute the surround processing by the
surround circuit 101.
[0093]
Fourth Embodiment FIG. 9 is an explanatory view schematically showing a configuration of a
sound reproducing apparatus 100 according to a fourth embodiment of the present invention.
08-05-2019
24
Here, the same components as those in FIG. 1 of the first embodiment are denoted by the same
reference numerals, and duplicate descriptions will be omitted.
[0094]
The fourth embodiment is effective when it is desired to reduce the amount of calculation of
signal processing as compared to the first embodiment described above, and the low frequency
signal is monaural processing.
That is, the addition unit 105 combines the left input signal S1L and the right input signal S1R to
generate a monaural input signal S1 ', and generates a low band signal S2' from the input signal
S1 '.
Then, the pseudo low band signal S7 'is generated by the same processing as the above first
embodiment.
[0095]
The pseudo low tone signal S7 'is added to the left input signal S1L by the adder 160L and
amplified by the amplifier 180L to reproduce the pseudo low band signal containing signal S8L
from the speaker 190L.
The pseudo low tone signal S7 'is added to the right input signal S1R by the adder 160R and
amplified by the amplifier 180R to reproduce the pseudo low band signal containing signal S8R
from the speaker 190R.
[0096]
In this case, since the pseudo low tone signal S7 'common to each channel is used, a DSP with
low processing capability can be used, and power consumption can be reduced. Fifth
08-05-2019
25
Embodiment FIG. 10 is an explanatory view schematically showing a configuration of a sound
reproducing apparatus 100 according to a fifth embodiment of the present invention. Here, the
same components as those of the fourth embodiment shown in FIG.
[0097]
In the fifth embodiment, as in the fourth embodiment described above, this is effective when it is
desired to reduce the amount of calculation of signal processing, and monaural processing is
performed for the low band signal. Further, in this configuration, the frequency f3 of the sine
wave signal S3 is set to a frequency band which is 12 times or less of the upper limit frequency
f2max passing through the filter unit 110 or the cutoff frequency fLPF and which can be
reproduced by the speaker 190.
[0098]
As a result, the filter unit 150 can be omitted, and when the sound reproducing apparatus 100 is
realized by digital signal processing, the amount of calculation of signal processing can be
suppressed more than in the fourth embodiment described above, and further, There is an
advantage that a low processing power DSP can be used and power consumption can be reduced.
[0099]
Sixth Embodiment FIG. 11 is an explanatory view schematically showing a configuration of a
sound reproducing apparatus 100 according to a sixth embodiment of the present invention.
Here, the same components as those in FIG. 1 of the first embodiment are denoted by the same
reference numerals, and duplicate descriptions will be omitted.
[0100]
In each of the above embodiments, a low frequency signal below the lowest resonance frequency
(see the speaker impedance characteristic in FIG. 12) that can not be reproduced by the speaker
190 is also amplified by the amplifier 180 and applied to the speaker 190. Here, according to the
08-05-2019
26
speaker impedance characteristic shown in FIG. 12, the impedance reaches a peak at the lowest
resonance frequency, and the impedance becomes close to the DC resistance of the voice coil in
the low band below that. In this case, power is consumed by the impedance of the voice coil even
if it is a low-pass signal that is not efficient and is not output as sound.
[0101]
Therefore, as shown in FIG. 11, the low band signal included in the input signal S1 is removed by
the filter unit 103 configured by a high pass filter or the like. In this case, the cutoff frequency of
the filter unit 103 is set near or above the upper cutoff frequency of the filter unit 110 that
extracts the low band signal S2. As a result, the low-frequency signal component that the speaker
190 can not reproduce easily is removed, and the low-frequency signal is artificially reproduced
in a frequency band that can be reproduced by the speaker 190.
[0102]
In this case, due to the equal sensitivity curve of the Robinson-Daddson curve, several dB to
several tens of dB are easily perceived even if the middle range is reproduced with the same
sound pressure than the low range, so the sound pressure is lower than the actual low range.
Even if it reproduces a low-pass signal, it is sufficiently perceived. Therefore, it is possible to
reduce the power consumption of the amplifier 180 because it is sufficient to reproduce the lowpass signal artificially reproduced at a level smaller than the original low-pass signal in order to
make the low-pass signal perceptible to the listener Become. That is, it is possible to suppress the
power consumption of the device or the entire system while performing reproduction of the low
frequency that can be perceived by the listener.
[0103]
The sixth embodiment using the filter unit 103 can be applied to each of the above-described
embodiments. <Other Embodiments (1)> In the above embodiments, the sound reproduction
device 100 is provided with the amplification unit 180 and the speaker 190. However, the
present invention is not limited to this.
[0104]
08-05-2019
27
That is, up to the amplification unit 180 may be configured as the sound reproduction device
100 so that any speaker can be freely connected. Further, up to the adding unit 160 may be
configured as the sound reproducing apparatus 100 so that an arbitrary amplification unit and
an arbitrary speaker can be freely connected.
[0105]
<Other Embodiments (2)> In the above embodiments, the sound reproduction device 100 is
provided with the amplification unit 180 and the speaker 190. However, the present invention is
not limited to this.
[0106]
That is, instead of the amplifying unit 180 and the speaker 190, various receiving devices (not
shown) are connected, and for a receiving device having a small-aperture speaker but not the
sound reproducing device 100 of the present embodiment, An acoustic transmitter or an acoustic
reproduction system that transmits an audio signal including a pseudo low band signal is also an
embodiment of the present invention.
[0107]
<Other Embodiments (3)> In the above embodiments, it has been described that a low-aperture
speaker can be used to perceive a low frequency signal by frequency conversion, but the
invention is limited to a small-aperture speaker is not.
[0108]
For example, when it is desired to reproduce a deep bass of about 20 Hz in a bookshelf type
speaker device, by using a pseudo low band signal S7 of 20 Hz intervals, a deep bass of about 20
Hz may be used as a basic sound by the missing fundamental for listeners. It will be felt
(perceivable).
[0109]
That is, also in this case, the listener is perceived as if there is the signal S2 of the frequency f2
which is below the lowest resonance frequency of the speaker 190 and is not actually
reproduced.
08-05-2019
28
Also, even when low-pass signals are hard to be perceived by the listener due to road noise from
tires, such as car audio, the low-pass signals are easily perceived by the listener by using the
frequency-converted pseudo low-pass signal S7. Area reproduction becomes possible.
[0110]
Also, when the original low frequency signal is difficult to be perceived by the listener due to the
noise around the place to be listened to, the user can listen by using the pseudo low frequency
signal S7 frequency-converted to the frequency apart from the noise frequency. This makes it
possible to reproduce low frequencies that are easily perceived by people.
In this case, the control unit may be configured to measure ambient noise and automatically
determine the frequency to be converted.
[0111]
DESCRIPTION OF SYMBOLS 100 sound reproduction apparatus 110 filter part 120 sine wave
signal source 130 1st multiplication part 140 2nd multiplication part 150 filter part 160
addition part 180 amplification part 190 speaker
08-05-2019
29
Документ
Категория
Без категории
Просмотров
0
Размер файла
43 Кб
Теги
jp2010183126
1/--страниц
Пожаловаться на содержимое документа