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JP2018032962

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DESCRIPTION JP2018032962
PROBLEM TO BE SOLVED: To provide an acoustic device capable of continuously giving a
speaker a sound signal in a region higher than the audible range as much as possible, and
capable of reliably protecting the speaker. SOLUTION: A sound signal of high and low
frequencies outside the audible band is extracted by a first fixed filter 4 and integrated by a level
integrator 6 to obtain a first integrated value a1. The sound signal in the low frequency band f
(ΔL) within the audible band is integrated by the second fixed filter 5 by the level integrator 6 to
obtain the second integrated value a2. The control unit 7 determines whether the high frequency
sound signal is dominant or not by comparing the first integrated value a1 and the second
integrated value a2, and when it is dominant, the variable filter 8 drives the high frequency
speaker Attenuate the signal. [Selected figure] Figure 1
Acoustic controller
[0001]
The present invention relates to an acoustic control device that performs control so as to always
give an optimal speaker drive signal to a speaker.
[0002]
If a direct current flows in the voice coil of the speaker, the voice coil does not vibrate and the air
cooling effect does not work, heat may be accumulated, the temperature may rise, and the voice
coil may be broken.
09-05-2019
1
Therefore, many techniques for preventing direct current from flowing through the voice coil
have been proposed. In addition, there are many proposals for limiting the output when it is
expected that heat accumulation will be large even if it is an alternating current to which the air
cooling effect works. Incidentally, it is considered that the amount of energy is originally small
for an ultra high frequency component that exceeds the human audible range, and there are
many cases where measures against this are not considered in particular. Technologies have also
been proposed that consider measures for regional constituents.
[0003]
In Patent Document 1, it is considered that there is a possibility that the output transistor and the
voice coil of the speaker may be destroyed if the input signal of the superhigh frequency
component given to the speaker becomes excessive. Therefore, in the conventional audio power
amplifier, a low pass filter for passing only the audible band for safety is provided to attenuate an
input signal of 20 kHz or more which is a superhigh frequency component higher than the
audible band.
[0004]
However, recently, music sources recording high frequency components above the audible band
are increasing, and it is becoming more common to input an ultra high frequency input signal of
this type of music source to a speaker.
[0005]
Therefore, Patent Document 1 discloses an invention relating to a power amplifier for an acoustic
signal in which the low pass filter is removed so as to be compatible with the music source and
an input signal having an ultrahigh frequency component exceeding the audible band can be
input. Have been described.
[0006]
The acoustic signal power amplification apparatus is provided with a high pass filter unit that
extracts an ultra high frequency component of frequency components of the input signal.
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2
The output signal from the high pass filter unit is input to the level control unit, where the gain is
adjusted so that the level of the ultra high frequency component does not exceed a
predetermined value.
[0007]
The present invention does not cut the input signal in the high frequency band above the audible
frequency band with the low pass filter as in the prior art, but directly outputs it to the speaker
without attenuating this ultra high frequency band component, When the level of is high, the
level of the ultra high frequency component is limited.
[0008]
JP, 2009-65427, A
[0009]
The power amplifier for an acoustic signal described in Patent Document 1 is to limit the level of
the ultra high frequency component when the level of the ultra high frequency component is
large.
However, since the voice coil is stopped and the air cooling effect does not work in the ultra high
frequency range where the voice coil follows and vibrates, the heat is accumulated even if the
level of the ultra high frequency component is not particularly large. And the voice coil may be
damaged.
In addition, although the heat is not accumulated in the voice coil and there is no fear of damage,
the level of the ultra high frequency component is limited, and the sound effect is reduced.
[0010]
The present invention solves the above-mentioned conventional problems, and a sound signal
higher than the audible band can be used as a speaker drive signal as much as possible, and the
acoustic effect can be enhanced, and the overheating and the breakage of the speaker can be
surely prevented. It is an object of the present invention to provide an acoustic control device
that can
09-05-2019
3
[0011]
The present invention is an acoustic control apparatus that processes a sound signal from a
sound source input unit to generate a speaker drive signal, comprising: a first fixed filter for
passing a sound signal in a frequency band higher than a first frequency; A level integrator for
obtaining a first integrated value obtained by integrating the level of the sound signal that has
passed through the fixed filter, and a control unit are provided, in the control unit, the first
integrated value exceeds a predetermined value. Sometimes, the frequency band higher than at
least the first frequency is limited.
[0012]
The acoustic control apparatus according to the present invention uses the first fixed filter or
another fixed filter associated therewith, in the frequency band lower than the second frequency
(where the second frequency <the first frequency). A sound signal is passed, and the level
integrator integrates the level of the sound signal in the frequency band higher than the first
frequency and the level of the sound signal in the frequency band lower than the second
frequency, It is preferable to obtain the first integrated value.
[0013]
The acoustic control apparatus according to the present invention is provided with a second fixed
filter for passing a sound signal of a low frequency band divided into a predetermined range in a
frequency band lower than the first frequency, and the level integrator Obtaining a second
integrated value obtained by integrating the level of the sound signal in the low frequency band;
and in the control unit, when the second integrated value is larger than the first integrated value,
It is further preferable not to limit frequency bands higher than the first frequency.
[0014]
Further, according to the acoustic control device of the present invention, a second fixing is made
to pass a sound signal of a low frequency band divided within a predetermined range in a
frequency band lower than the first frequency and higher than the second frequency. A filter is
provided, and a second integrated value obtained by integrating the level of the sound signal in
the low frequency band is obtained by the level integrator, and the control unit is configured to
calculate the second integrated value with respect to the first integrated value. It is further
preferable not to limit the frequency band higher than the first frequency of the speaker drive
signal when it is large.
[0015]
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4
For example, in the acoustic control device according to the present invention, when the first
integrated value exceeds the predetermined value and the second integrated value is lower than
the predetermined value in the control unit, at least the first frequency is set. It limits high
frequency bands.
[0016]
Further, in the audio apparatus according to the present invention, the audio apparatus further
includes a frequency variable unit that changes a frequency distribution of the speaker drive
signal, and the control unit controls the frequency variable unit to control the first frequency of
the speaker signal. It limits the higher frequency band.
[0017]
In the resonance control device of the present invention, the first frequency is set to any value
within the range of 18 to 28 kHz.
[0018]
Also, the second frequency is set to any value within the range of 5 to 50 Hz.
Furthermore, the low frequency band is divided within the range of 20 Hz to 500 Hz.
[0019]
In the sound control apparatus according to the present invention, the control unit may perform
tone adjustment using the integrated value from the level integrator.
[0020]
The acoustic control device according to the present invention integrates the level of the sound
signal in the frequency band higher than the first frequency by the level integrator to obtain a
first integrated value, and the first integrated value exceeds a predetermined value. And limits the
frequency band higher than the first frequency of the speaker drive signal.
09-05-2019
5
Even when the level of the signal higher than the first frequency is high, it can be given to the
speaker as long as the first integrated value does not exceed the predetermined value, so the
acoustic effect can be maintained high.
In addition, even if the level of the signal in the higher region than the first frequency is lower, if
the first integrated value exceeds the predetermined value, the frequency band higher than the
first frequency is limited, so overheating and breakage of the speaker may occur. Can be reliably
prevented.
[0021]
Further, by providing a second fixed filter to extract a sound signal in a low frequency band and
adding a second integrated value obtained by integrating the signal level in the low frequency
band, it is possible to maintain the acoustic effect.
If the second integrated value is large and the sound signal level in the low frequency band is
high, the voice coil amplitude is large and the cooling effect is high, and the temperature rise is
suppressed. Level of the sound signal is not limited, and even if the high frequency level of the
sound signal is increased and the first integrated value is increased, the high frequency sound
signal at a higher level than the first frequency is obtained. It becomes possible to use it and it is
possible to further enhance the sound effect.
[0022]
FIG. 2 is a block diagram of the acoustic device according to the embodiment of the present
invention, a follow chart showing an example of control operation in the control unit shown in
FIG. 1, a line showing the relationship between the frequency of the speaker drive signal given
the voice coil of the speaker and the coil temperature. Figure,
[0023]
FIG. 1 shows a block diagram of the acoustic control device 1 according to the embodiment of
the present invention.
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6
The sound control device 1 has a sound source input unit 2.
A sound signal input from the sound source input unit 2 is given to the volume / tone adjustment
unit 3.
The volume and tone adjustment unit 3 can artificially adjust the volume and the reproduction
tone through an operation unit (not shown), but the adjustment operation is also performed by a
control signal from the control unit 7 described later.
[0024]
The sound signal adjusted by the volume / tone adjustment unit 3 is given to the first fixed filter
4 and the second fixed filter 5.
[0025]
The first fixed filter 4 passes a sound signal higher than the first frequency f1 and a sound signal
lower than the second frequency f2 and passes between the first frequency f1 and the second
frequency f2. Attenuate or block sound signals in the frequency band.
[0026]
The first fixed filter 4 passes sound signals outside the range of the human audible band, and the
first frequency f1 is any value within the range of 18 to 28 kHz, which is a value near the upper
limit frequency of the audible range. It is set to the value of
Preferably, the first frequency f1 is set to any value within the range of 18 to 22 kHz.
In the first fixed filter 4 of the embodiment shown in FIG. 1, the first frequency f1 is set to 20
kHz.
[0027]
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The second frequency f2 is set to any value in the range of 5 to 50 Hz, which is a value near the
lower limit frequency of the audible range.
Preferably, the second frequency f2 is set to any value within the range of 10 to 30 Hz.
In the first fixed filter 4 of the embodiment shown in FIG. 1, the second frequency f2 is set to 20
Hz.
[0028]
The first fixed filter 4 is a combination of a high pass filter (HPF) whose cutoff frequency is 20
kHz of the first frequency f1 and a low pass filter (LPF) whose cutoff frequency is 20 Hz of the
second frequency f2 It is configured as one element.
Alternatively, a high pass filter (HPF) and a low pass filter (LPF) configured as separate elements
may be used in combination.
[0029]
The second fixed filter 5 is a sound signal of a low frequency band f (L1 to L2) relatively lower
than the first frequency f1 (20 kHz) and higher than the second frequency f2 (20 Hz) and
relatively low. A band pass filter (BPF) that allows
The low frequency band f (L1 to L2) selected here is set in a range where the voice coil amplitude
is large when the speaker is driven, and a cooling effect on the voice coil can be expected. The
low frequency band f (L1 to L2) is a frequency band divided within the range of 20 Hz to 500 Hz,
and the low frequency band f (L1 to L2) of the second fixed filter 5 shown in FIG. Pass the sound
signal in the range of 300 Hz.
[0030]
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8
The sound signal that has passed through the first fixed filter 4 and the sound signal that has
passed through the second fixed filter 5 are provided to the level integrator 6. The level
integrator 6 obtains a value obtained by integrating the level (intensity) of the sound signal over
time. The level of the sound signal of the ultrahigh frequency above (or above) the first frequency
f1 (20 kHz) passed through the first fixed filter 4 is integrated for a predetermined time, and the
first fixed filter 4 is passed through the first The level of the sound signal of an ultra-low
frequency lower than (or less than) the frequency f2 of 2 (20 Hz) is also integrated for a
predetermined time. The sum of the integrated value of the level of the sound signal exceeding
the first frequency f1 and the integrated value of the level of the sound signal lower than the
second frequency f2 is a first integrated value a1.
[0031]
The sound signal in the low frequency band f (L1 to L2) (50 Hz to 300 Hz or less) that has
passed through the second fixed filter 5 is also sent to the level integrator 6, and the signal level
integrates the signal that has passed through the first fixed filter 4. The second integrated value
a2 is obtained by integration at the same time as Then, the first integrated value a1 and the
second integrated value a2 are sent to the control unit 7.
[0032]
The control unit 7 controls the cut frequency of the variable filter 8 which is a frequency variable
unit or on / off control based on the first integrated value a1 and the second integrated value a2.
The control unit 7 can also adjust the volume / tone adjustment unit 3 based on the first
integrated value a1 and the second integrated value a2.
[0033]
Among the sound signals adjusted by the volume / tone adjustment unit 3, the signal of the
frequency band row passing through the variable filter 8 is given as the speaker drive signal Sr to
the power amplifier 10 and given to the voice coil of the speaker 11 , Speaker 11 is driven.
[0034]
Next, the operation of the acoustic control device 1 will be described.
09-05-2019
9
FIG. 3 (A) shows the temperature change of the voice coil when a speaker drive signal of 10 Hz,
which is an ultra-low frequency near the direct current lower than the audible band, is applied to
the speaker. The temperature change of the voice coil when the speaker drive signal of 40 kHz
which is a super high frequency beyond the audible band is given to the speaker is shown. In
each case, the horizontal axis represents the passage of time (minutes), and the vertical axis
represents the temperature of the voice coil. In FIGS. 3 (A) and 3 (B), the temperature rise was
measured using a two-way speaker whose diameter of the cone (diaphragm) is 17 cm.
[0035]
In FIG. 3 (A), a temperature change of the voice coil is shown by a diagram (i) when a sine wave
of a single frequency of 10 Hz is given to the voice coil as a speaker drive signal and driven at 20
W. The change of the ambient temperature (room temperature) is shown in (ii).
[0036]
In FIG. 4 (B), a temperature change of the voice coil is shown by a diagram (iii) when a single
frequency sine wave of 40 kHz is given to the voice coil as a speaker drive signal and driven at
20 W. The change in ambient temperature is shown in (iv).
[0037]
According to the result in FIG. 3A, when a speaker drive signal of an ultra low frequency lower
than about 20 Hz which is the lower limit of the audible band is applied to the speaker, the
temperature of the voice coil is 30 ° C. in 14 minutes. Ascend to some extent.
According to the result in FIG. 3B, when a speaker drive signal of an ultra-high frequency above
the upper limit of 20 kHz, which is the upper limit of the audible band, is applied to the speaker,
the temperature of the voice coil is about 70.degree. To rise.
[0038]
As described above, when a very low frequency speaker drive signal or a very high frequency
speaker drive signal exceeding the audible band is applied to the voice coil of the speaker 11, the
09-05-2019
10
voice coil hardly moves and air around the voice coil Since it is not stirred, the heat of the voice
coil can not be dissipated sufficiently toward the surrounding space.
As a result, the voice coil is likely to have high heat and the risk of breakage is increased.
[0039]
Therefore, the first fixed filter 4 extracts a sound signal of a frequency above (or above) 20 kHz,
which is the first frequency f1, and a sound signal of a frequency of 20 Hz or less (or less), which
is the second frequency f2. Then, the level integrator 6 calculates a first integrated value a1
obtained by adding the integrated value of the level of the sound signal exceeding 20 kHz and
the integrated value of the level of the sound signal of 20 Hz or less. When it is determined that
the first integrated value a1 is too high, the control unit 7 controls the variable filter 8 so as to
suppress the speaker drive signal of the very high frequency band from being supplied to the
voice coil.
[0040]
On the other hand, the frequency of the 50 Hz to 300 Hz sound signal extracted by the second
fixed filter 5 is in the audible band. When a sound signal of this low frequency band f (L1 to L2)
is given to the voice coil of the speaker 11, the voice coil vibrates with a considerably large
amplitude. As a result, the air around the voice coil is agitated, the heat generated in the voice
coil is easily released to the air, and the cooling effect is enhanced.
[0041]
Therefore, the control unit 7 performs an operation from the first integrated value a1 of the level
of the sound signal that has passed through the first fixed filter 4 and the second integrated
value a2 of the level of the sound signal that has passed through the second fixed filter 5 Thus,
the pass band of the variable filter 8 which is a frequency variable unit is variably controlled.
[0042]
FIG. 2 shows a flowchart of the processing operation of the control unit 7.
09-05-2019
11
The control unit 7 mainly includes a CPU and a memory.
[0043]
In step 1 (ST1) shown in FIG. 2, when the first integrated value a1 and the second integrated
value a2 are given to the control unit 7, the control unit 7 adds the value of the second
integrated value a2, and It is determined whether or not the 1 integrated value a1 is large, and it
is determined whether or not the pass frequency of the variable filter 8 is to be changed.
[0044]
In ST2, when it is determined that the first integrated value a1 exceeds (is above) the first
threshold and the second integrated value a2 is less than (or less than) the second threshold ,
ST3 to change the pass frequency band of the variable filter 8 to a narrow band.
In ST2, when the condition that the first integrated value a1 exceeds the first threshold and the
second integrated value a2 is less than or equal to the second threshold is not satisfied, the
process proceeds to ST4. Thus, the pass frequency of the variable filter 8 is made to be a wide
band.
[0045]
That is, even if the value of the first integrated value a1 obtained by integrating the levels of the
sound signal exceeding the first frequency f1 and the sound signal below the second frequency is
high, the sound signal of the low frequency band f (L1 to L2) If the second integrated value a2
obtained by integrating the levels is high, the control rate of the sound signal of 50 to 300 Hz
exceeds a predetermined ratio, and it is possible to provide a sufficient cooling effect to the voice
coil. At this time, even if the variable filter 8 has a wide band and a speaker drive signal in a high
frequency band exceeding 20 kHz is applied to the voice coil, the risk of the voice coil being
damaged by excessive heat can be reduced.
[0046]
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12
On the other hand, the value of the first integrated value a1 obtained by integrating the levels of
the sound signal exceeding the first frequency f1 and the sound signal below the second
frequency is high and the sound signal of the low frequency band f (L1 to L2) When the second
integrated value a2 obtained by integrating the levels is low, the frequency at which the voice
coil is vibrated with a large amplitude is low in the low frequency band, and a cooling effect on
the voice coil can not be sufficiently expected. Thus, the speaker drive signal in the ultrahigh
frequency band above 20 kHz is attenuated. Alternatively, it shuts off a speaker drive signal in an
ultra high frequency band exceeding 20 kHz.
[0047]
The control unit 7 compares the first integrated value a1 with the second integrated value a2,
and calculates, for example, a ratio (a1 / (a1 + a2)) of the first integrated value a1, and this ratio
is a predetermined threshold value. The variable filter 8 may be changed to a narrow band to
attenuate the speaker drive signal of an ultra high frequency band exceeding 20 kHz, or to block
the speaker drive signal of an ultra high frequency band exceeding 20 kHz.
[0048]
Alternatively, the ratio (a2 / (a1 + a2)) of the second integrated value a2 may be calculated, and
the variable filter 8 may be changed to a narrow band when this ratio becomes less than (or less
than) a predetermined threshold.
[0049]
The setting for narrowing the variable filter 8 in ST3 may block signals of a frequency of 20 kHz
or more exceeding the audible band, or 20 kHz exceeding the audible band according to the level
of the first integrated value a1 and the ratio. The attenuation factor of the signal of the above
frequency may be changed.
Alternatively, the frequency band for passing the wide band in the variable filter 8 may be
changed within the range of 20 kHz to 40 kHz according to the level of the first integrated value
a1 and the ratio.
[0050]
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13
When the acoustic control device 1 is used, even in the case where the level of the sound signal
of the first frequency f1 or more and the level of the sound signal of the second frequency f2 or
less are high, in the low frequency band f (L1 to L2) If the integrated value of the voice level is
high, heating of the voice coil can be prevented and temperature rise can be suppressed.
Therefore, in this case, the speaker drive signal Sr of high frequency of 20 kHz or more can be
given to the power amplifier 10, and it becomes possible to form the sound including the sound
signal of high frequency.
[0051]
In the acoustic control device 1 shown in FIG. 1, when it is determined that the numerical value
of the first integrated value a1 is high, the volume / tone adjustment is performed with the
adjustment of the variable filter 8 or without performing the adjustment of the variable filter 8. A
control signal is given to the part 3, and tone adjustment of the sound signal, that is, adjustment
to reduce the level of the high frequency component is also performed.
[0052]
Hereinafter, modifications of the embodiment of the present invention will be described.
First Modification In the block diagram shown in FIG. 1, the first fixed filter 4 extracts only the
sound signal having a frequency of 20 kHz or higher, which is the first frequency, and supplies
the extracted signal to the level integrator 6. Only the level of the sound signal of the frequency
may be integrated to calculate the first integrated value a1. In this case, it is preferable to remove
a sound signal of 20 kHz or less by a low pass filter before being input to the sound source input
unit 2.
[0053]
Second Modified Example In the block diagram shown in FIG. 1, without providing the second
fixed filter 5, a first integrated value obtained by integrating the levels of the sound signal of
frequencies higher than the first frequency f1 in the level integrator 6. The first integrated value
a1 is obtained by taking a1 or taking into account the level integrated value of frequencies below
the second frequency f2, and the control unit 7 uses only the value of the first integrated value
a1 (second The variable filter 8 may be controlled without using the value a2.
09-05-2019
14
[0054]
For example, even if the level of the high-range sound signal exceeding 20 kHz is temporarily
high, there is no damage to the voice coil if it appears only occasionally without continuing for a
long time.
Therefore, when the value of the first integrated value a1 obtained by integrating the level of the
sound signal of the frequency higher than the first frequency f1 is low, the signal is given to the
speaker 11 even if the level of the high frequency sound signal is high. This makes it possible to
reproduce sound that makes use of the originality of the sound source.
[0055]
DESCRIPTION OF SYMBOLS 1 sound control apparatus 2 sound source input part 4 1st fixed
filter 5 2nd fixed filter 6 level integrator 7 control part 8 variable filter 11 speaker a1 1st
integrated value a2 2nd integrated value f1 1st frequency f2 2nd Frequency f (ΔL) low
frequency band
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