JP2005223385

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DESCRIPTION JP2005223385
The present invention relates to an electroacoustic reproducing apparatus in which a speaker is
built in an enclosure, and suppressing the influence on the frequency sound pressure
characteristic of the speaker based on the resonance caused by the fixing of the enclosure and
the resonance of the apparatus itself. It is the purpose. An electric sound reproducing apparatus
according to the present invention is provided with a vibration detection device 5 on a bracket
which is an enclosure 2 or a support member 3 and negatively feedbacks a detected signal to an
amplifier 4 for driving a speaker 1. The vibration of the support member 3 is corrected and
reduced to prevent the generation of the resonance sound and to improve the sound quality.
[Selected figure] Figure 1
Electro-acoustic playback device
[0001]
TECHNICAL FIELD The present invention relates to an electroacoustic reproducing apparatus
configured by an enclosure such as a speaker box incorporating a speaker or the like.
[0002]
The prior art will be described with reference to FIG. 5 and FIG.
FIG. 5 is a block circuit diagram of a conventional electroacoustic reproducing apparatus, and
FIG. 6 is a mechanical equivalent circuit diagram thereof. According to the figure, 1 is a speaker
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which is an electroacoustic transducer and 2 is a speaker 1 An internally mounted enclosure 3 is
a support member for fixing the enclosure 2 to an indoor floor or a floor of a vehicle, 8 is an
input of an audio signal of the amplifier 4 whose output signal is input to the speaker 1 It is a
terminal and is connected to an output unit of an audio signal from an external device (not
shown).
[0003]
The above-mentioned electroacoustic reproducing apparatus receives an external audio signal at
the input terminal 8, amplifies it by the amplifier 4, inputs this amplified audio signal to the
speaker 1, and emits the sound from the speaker 1 into the vehicle interior or room It is.
[0004]
Although the amplifier 4 has been described as being outside the enclosure 2 in the prior art, it
may be installed in the enclosure 2.
[0005]
As prior art document information on the invention of this application, there is, for example,
Patent Document 1.
Japanese Patent Application Laid-Open No. 10-32895
[0006]
However, in the electroacoustic reproducing apparatus as described above, as shown in the
mechanical equivalent circuit diagram of FIG. 6, the vibration system mass of the speaker 1 on
the resonance system of the compliance 15 of the support member 3 and the mass 14 of the
enclosure 2 Since the resonance system of the support system compliance 12 of the speaker 1
and the speaker 1 is connected, when the audio signal is amplified by the amplifier 4 and the
speaker 1 is driven, the driving force is the vibration system mass 11 of the speaker 1 and the
enclosure Between the mass 14 and the same size in the opposite direction, resonance occurs
under the influence of each resonance system to affect the sound pressure frequency
characteristics of the sound emitted from the speaker 1, and electroacoustic reproduction It was
also the cause of noise generation of the device itself.
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[0007]
Here, 13 represents the mechanical resistance of the support system of the speaker, and 16
represents the mechanical resistance of the support member 3.
[0008]
The present invention solves the problems as described above by suppressing resonance and
provides an electroacoustic reproduction device with excellent acoustic characteristics.
[0009]
In order to solve the problems as described above, an electroacoustic reproducing apparatus
according to claim 1 of the present invention amplifies an input signal and outputs the amplified
signal to a speaker mounted in an enclosure, and a support member of the enclosure An electroacoustic reproduction device fixed to the other by a detection means for detecting the vibration
of the enclosure or the support member, and a negative feedback circuit for negatively feeding
back the vibration signal detected by the detection means to the amplifier The resonance of the
enclosure and / or the support member is suppressed to suppress the generation of abnormal
noise and improve the acoustic characteristics of the electroacoustic reproduction device.
[0010]
According to a second aspect of the present invention, an acceleration sensor is used as the
detection means according to the first aspect, and an integration circuit is provided in the signal
processor together with the availability as a sensor. It has the ease of handling that conversion to
speed signals and amplitude signals can be easily performed.
[0011]
According to a third aspect of the present invention, the vibration detected by the detection
means according to the first aspect is negatively fed back as a vibration signal proportional to the
velocity to reduce the sharpness of the mechanical resonance of the support member. Control
can be made possible and contribution can be made by suppression of vibration.
[0012]
According to a fourth aspect of the present invention, the vibration signal according to the third
aspect is negatively fed back to the amplifier through the low pass filter, and a high frequency
band with a large fluctuation in phase is cut to obtain a negative feedback circuit. It is intended to
be stabilized.
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[0013]
According to a fifth aspect of the present invention, the cutoff frequency of the low-pass filter
according to the fourth aspect is set to a frequency lower than a resonance frequency determined
by the mass of the enclosure and the compliance of the support member. In addition to the cut of
the region, the phase change of the low pass filter itself at the resonance frequency is reduced to
facilitate the handling in the signal processor.
[0014]
According to claim 6 of the present invention, the low pass filter according to claim 4 or claim 5
is an even-order filter, and the phase of the output with respect to the input of the low pass filter
is 0 degrees or 180 degrees. It is possible to simplify the processing circuit in the signal
processor at the time of the negative feedback circuit configuration via the mixer to the amplifier.
[0015]
As described above, the electroacoustic reproduction device of the present invention is provided
with means for detecting the vibration of the enclosure or the support member of the enclosure,
and the enclosure detected by this detection means is negatively fed back to the amplifier for
driving the speaker. And / or the resonance of the support member is suppressed to suppress the
generation of abnormal noise and improve the acoustic characteristics of the electroacoustic
reproducing apparatus.
[0016]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
In the description, the same parts as those of the conventional speaker used in the description of
the background art are denoted by the same reference numerals.
[0017]
Embodiment 1 FIG. 1 is a block diagram of an embodiment of an electro-acoustic reproduction
device according to the present invention, and FIG. 2 (a) is a machine applied to the electroacoustic reproduction device inputted to the voice input terminal. FIG. 2B is a voltage
characteristic diagram showing alternative voltage characteristics for generating resonance, and
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FIG. 2B shows the amplitude characteristics of the support member at the time of voltage
application of FIG. FIG. 2 (c) is an amplitude characteristic chart compared by presence or
absence, and FIG. 2 (c) shows the amplitude of the same support member when the frequency is
swept with a sine wave input to the voice input terminal according to the presence or absence of
the negative feedback circuit of this embodiment. It is a characteristic view compared, and
especially the invention according to claims 1 to 3 will be described with reference to the same
drawing.
[0018]
According to the figure, 1 is an electroacoustic transducer such as a speaker, 2 is an enclosure 2
such as a speaker box, and the speaker 1 is attached.
Further, the enclosure 2 is fixed to a floor surface such as indoors or a vehicle by a support
member 3.
An amplifier 4 has an input terminal 8 for an audio signal from an external device (not shown).
[0019]
The above-described electroacoustic reproducing apparatus is the same as the prior art, but in
the present embodiment, the vibration detecting device 5 is mounted on the supporting member
3 as the vibration detecting means.
The vibration detection device 5 converts the vibration of the support member 3 into an electric
signal, and the converted electric signal is a signal suitable for negative feedback via the signal
processor 6 connected to the vibration detection device 5. It is generated, mixed with the voice
input signal in the mixer 7 and input to the amplifier 4.
[0020]
In the signal processor 6, amplification is performed when the detection signal of the vibration
detection device 5 is small, and amplification is performed only for a desired control band such
as a mechanical resonance frequency or the like, or cutting frequencies in other bands Electrical
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signal processing of
[0021]
As described above, the electrical signal corresponding to the magnitude of the mechanical
vibration detected by the vibration detection device 5 is negatively fed back, and is input to the
speaker 1 through the amplifier 4 to perform the above-mentioned (of the enclosure 2 and the
support member 3) machine It controls and controls vibration.
[0022]
In the above embodiment, the vibration detection device 5 is described as being mounted on the
support member 3. However, since the same mechanical vibration is detected, the vibration
detection device 5 may be mounted on the enclosure 2 .
[0023]
Next, the effects will be described with reference to FIGS. 2 (a) to 2 (c). When a voltage having a
waveform as shown in FIG. 2 (a) is input to the input terminal 8 as an audio input signal, the
maximum vibration occurs at the rise of this input. It occurs and gradually declines.
This state is shown in FIG. 2 (b), where the line a shows the damping characteristics of the
vibration of the support member 3 of the electroacoustic reproducing apparatus of the present
embodiment, and the line b is the conventional electroacoustic for comparison. Although the
damping characteristic of the vibration of the supporting member 3 of the reproducing
apparatus is shown, it can be seen that the line b vibrates for a long time more than the line a.
[0024]
It is understood from the figure that the use of the negative feedback circuit of this embodiment
suppresses the vibration.
[0025]
FIG. 2 (c) shows the amplitude of the support member 3 when a sweep input signal is applied to
the input terminal 8 by sweeping the frequency, but the line a (amplitude characteristics of the
support member by the electroacoustic reproducing apparatus of this embodiment It can be
understood that) is more suppressed than the line b (the amplitude characteristic of the support
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member by the conventional electroacoustic reproducing apparatus).
[0026]
In addition, as the amplitude detection apparatus 5, a known acceleration sensor or speed sensor
is used.
The acceleration sensor is a signal proportional to the acceleration, but by providing an
integration circuit in the signal processor 6, it can be easily converted into a velocity signal or an
amplitude signal, and can be easily obtained.
[0027]
In addition, by setting the signal returned to the mixer at the front stage of the amplifier to be a
signal proportional to the vibration velocity of the support member by an acceleration sensor or
the like, control can be made possible to reduce the sharpness of mechanical resonance of the
support member. It can contribute by suppression of
[0028]
(Embodiment 2) FIG. 3 is a block diagram of another embodiment of the electroacoustic
reproducing apparatus of the present invention, FIG. 4 (a) is an amplitude characteristic diagram
of the support member, and FIG. FIG. 16 shows gain frequency characteristics of a low pass filter
which is a digital signal processing unit, and in particular, the inventions according to claims 4 to
6 will be described. The same reference numerals as in the first embodiment denote the same
parts. To explain.
A signal processor 9 replaces the signal processor 6 of the first embodiment, and is provided
with a low pass filter at the front stage.
[0029]
Noting that the low frequency component of vibration is the cause of abnormal noise etc., the
high frequency component is small, and the change in phase is also hard to obtain the
suppression effect by feedback, so it is difficult to cut the high frequency component Therefore, it
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is possible to apply negative feedback more stably.
[0030]
The cutoff frequency of the low pass filter is preferably a frequency lower than the resonant
frequency determined by the mass of the enclosure 2 and the compliance of the support member
3, and the position of the resonant frequency comes during the attenuation of the cutoff
frequency of the low pass filter. It is desirable to set as such, and still further, it should be set to a
more stable position of the phase.
[0031]
That is, as apparent from FIG. 4 (a), the resonance frequency between the enclosure 2 and the
support member 3 is around 60 Hz, and the cutoff frequency of the low pass filter is set to
around 15 Hz below that in FIG. 4 (b) By setting the point of this resonance frequency in the
middle of the attenuation of the gain of the low pass filter, the vibration signal at the time of the
sharp resonance is attenuated with the cut of the high region and the handling in the signal
processor 9 becomes easy. It is something like that.
[0032]
Furthermore, in the present embodiment, as shown in FIG. 4 (b), the smooth position of the phase
characteristic (the change of the phase (slope d) near the cutoff frequency is steep, and the foot
is inclined (c)) Since the position of the resonance frequency is set to be slow), the phase
fluctuation is small and the negative feedback circuit becomes stable, and the vibration
suppression effect can be stably obtained.
[0033]
Also, although the low pass filter of the signal processor 9 in the present embodiment is provided
as an even order filter, the phase of the output with respect to the input of the low pass filter is 0
degrees or 180 degrees by making it even order. The processing circuit in the signal processor 9
is prevented from being complicated when the negative feedback circuit is configured via the
mixer 7.
[0034]
The electroacoustic reproducing apparatus according to the present invention is effective in
suppressing resonance due to mechanical vibration including an enclosure and a support
member, and is effective in preventing generation of abnormal noise due to mechanical vibration
based on resonance of the acoustic device. It is a thing.
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[0035]
Also, the amplifier may be mounted within the enclosure or outside the enclosure, and the scope
of application of the present invention is for use in a wide range of audio equipment.
[0036]
Block diagram of one embodiment of electro-acoustic reproduction device of the present
invention (a) Voltage characteristics showing alternative voltage characteristics for generating
mechanical resonance applied to the electro-acoustic reproduction device input to the same
audio input terminal (B) Amplitude characteristic diagram comparing the amplitude
characteristic of the support member at the time of voltage application in FIG. 2 (a) with and
without the negative feedback circuit in this embodiment, (c) Frequency of sine wave at the same
voice input terminal Of the amplitude of the same support member when sweeping and input by
comparing the presence or absence of the negative feedback circuit of the present embodiment.
Block diagram of another embodiment of the electroacoustic reproducing apparatus of the
present invention (a) same support Amplitude characteristic diagram of the member, (b) Gain
frequency characteristic diagram of the low pass filter which is the main part Block diagram of
the conventional electroacoustic reproducing apparatus Same mechanical equivalent circuit
diagram
Explanation of sign
[0037]
Reference Signs List 1 speaker 2 enclosure 3 support member 4 amplifier 5 vibration detection
device 6 signal processor 7 mixer 8 input terminal 9 (with low pass filter) signal processor
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