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JPH10234095

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DESCRIPTION JPH10234095
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound reproducing apparatus particularly suitable for use in vehicles.
[0002]
2. Description of the Related Art FIG. 6 shows a block diagram of a conventional sound
reproducing apparatus. In FIG. 6, a reproduced signal from a signal source 1 such as a CD player,
a radio receiver, a tape recorder, etc. The signal is input to the power amplifier 3 for power
amplification, and the signal output from the power amplifier 3 is input to the speaker 4 for
reproduction.
[0003]
On the other hand, a microphone 5 is disposed around the speaker 4, and the microphone 5
collects the reproduced sound component from the speaker 4 and an extraneous noise
component of about 100 Hz or less around the speaker.
[0004]
The output signal from the microphone 5 is amplified by the microphone amplifier 6 and fed
back to the subtracter 2, thereby acting to attenuate extraneous noise components in the
reproduced sound field.
08-05-2019
1
[0005]
However, in the conventional sound reproducing apparatus, since the extraneous noise
component VN and the reproduced sound component VM are fed back to the reproduction signal
by the microphone amplifier 6, not only the extraneous noise component but also the
reproduction is reproduced. The sound component is also reduced in the low band, and there is a
problem that the balance of reproduction frequency characteristics is broken as shown by the
broken line in FIG.
[0006]
An object of the present invention is to provide an acoustic reproduction device that attenuates
extraneous noise components by means of a feedback loop, but has no imbalance in reproduction
frequency.
[0007]
SUMMARY OF THE INVENTION In order to solve this problem, the present invention is provided
with a filter for correcting the reproduction frequency characteristic when the extraneous noise
component is attenuated.
[0008]
As a result, the extraneous noise component can be attenuated without the loss of balance of the
reproduction frequency.
[0009]
The invention according to claim 1 of the present invention is a reproduction system including a
power amplifier for amplifying a reproduction signal from a signal source, and a speaker for
reproducing a signal output from the power amplifier. A microphone disposed around the
speaker and provided on the input side of the power amplifier, and a microphone for picking up
the reproduced sound component by the speaker and external noise components around the
speaker, and subtracting the output signal from the microphone from the reproduced signal A
sound reproducing apparatus comprising: a feedback system including a subtractor for
attenuating extraneous noise components; and a filter for correcting the reproduction frequency
characteristic at the time of attenuation of the extraneous noise components in either the
reproduction system or the feedback system. It has the effect that the balance of the
reproduction frequency characteristics is not lost when the extraneous noise component is
attenuated.
08-05-2019
2
[0010]
The invention according to claim 2 of the present invention is the sound reproduction apparatus
according to claim 1, characterized in that the filter has the inverse characteristic of the feedback
transfer function, and attenuates the extraneous noise component without the balance of the
reproduction frequency being lost. It has the effect of
[0011]
The invention according to claim 3 of the present invention is a reproduction system including a
power amplifier for amplifying a reproduction signal from a signal source and a speaker for
reproducing a signal output from the power amplifier, and arranged around the speaker A
microphone for picking up the reproduced sound component by the speaker and an extraneous
noise component around the speaker, and an input side of the power amplifier, which subtracts
the output signal from the microphone from the reproduced signal to attenuate the extraneous
noise component A noise detection means for extracting only an extraneous noise component by
subtracting an output signal from the microphone and a reproduction signal from the signal
source, and outputting the noise by the output of the noise detection means. A sound
reproduction apparatus configured to change the filter characteristics of a variable filter
provided in the system, and the balance of the reproduction frequency is not broken. It has the
effect of attenuating the coming noise component.
[0012]
The invention according to claim 4 of the present invention is a reproduction system including a
power amplifier for amplifying a reproduction signal from a signal source and a speaker for
reproducing a signal output from the power amplifier, and arranged around the speaker A
microphone for picking up the reproduction component by the speaker and an external noise
component around the speaker, and a subtracter provided on the input side of the power
amplifier and subtracting an output signal from the microphone from the reproduction signal to
attenuate the external noise component And the feedback system is configured to vary the
feedback amount according to the magnitude of the external noise component, and the
reproduction system is provided with a variable filter having the inverse characteristic of the
feedback transfer function, The sound reproducing apparatus is configured such that the variable
filter has variable filter characteristics according to the size of the extraneous noise component,
and the variable filter is configured according to the size of the extraneous noise component.
Changing the Kaeryou, it has the effect of varying the filter characteristics for correcting the
reproduction frequency characteristic according to external noise component corresponding to
the feedback amount.
[0013]
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3
The invention according to claim 5 of the present invention is the sound reproduction apparatus
according to claim 4, further comprising noise detection means for extracting an extraneous
noise component by subtracting a reproduction signal from a signal source from an output signal
from a microphone. The invention according to claim 4 has the same function.
[0014]
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to
5.
(First Embodiment) FIG. 1 is a block diagram of a first embodiment of a sound reproducing
apparatus according to the present invention.
In FIG. 1, reference numeral 11 denotes a signal source such as a CD player, a radio receiver, and
a tape recorder, and a reproduction signal from the signal source 11 is input to a subtractor 12.
The subtractor 12 subtracts an output signal from a microphone 15, which will be described
later, and the reproduction signal, inputs the output thereof to the power amplifier 13, and
amplifies the power.
The signal output from the power amplifier 13 is input to the speaker 14 and reproduced.
A microphone 15 is disposed around the speaker 14, and the microphone 15 collects a
reproduced sound component VM from the speaker 14 and an extraneous noise component VN
around the speaker.
An output signal from the microphone 15 is amplified by the microphone amplifier 16 and input
to the subtractor 12 to be negatively fed back with respect to the reproduction signal.
Here, a filter 17 is provided at the front stage of the subtractor 12, and is configured to apply a
reproduction signal to the subtractor 12 through the filter 17.
08-05-2019
4
[0015]
Now, the reproduction signal from the signal source 11 is Vin, the characteristic of the filter 17 is
TF, the output of the subtractor 12 is Vo / A, the amplification degree of the power amplifier 13
is A, the output of the power amplifier 13 is Vo, the characteristic of the speaker 14 If Tsp, the
reproduction output of the speaker 14 is VM, and the external noise is VN, the output signal of
the microphone 15 is VN + VM, and is converted to VN + VoTsp.
Therefore, the output Vo / A of the subtractor 12 is Vo / A = VinTF− (VN + VoTsp) (Expression
1), and the output Vo of the power amplifier 13 is Vo = AVinTF−AVN−AVoTsp (Expression 2)
Vo (1 + ATsp) = AVinTF-AVN (formula 3) Vo = (A / 1 + ATsp) TFVin- (A / 1 + ATsp) VN (formula
4).
Here, if the characteristic TF of the filter 17 is set to TF = (1 + ATsp) / A (equation 5), the output
Vo of the power amplifier 13 is Vo = Vin− (A / 1 + ATsp) · VN (equation 6) .
By making the characteristic of the filter 17 an inverse characteristic of the feedback transfer
function as shown by the solid line in FIG. 2 in this manner, the reproduction frequency
characteristic of the output reproduced by the speaker 14 is flat as shown by the solid line in FIG.
As a result, the external noise VN can be attenuated and, at the same time, the characteristic can
be corrected so that there is no frequency variation.
[0016]
Second Embodiment FIG. 3 is a block diagram of a sound reproducing apparatus according to a
second embodiment of the present invention.
In FIG. 3, reference numeral 11 denotes a signal source, and a reproduction signal from the
signal source 11 is input to a subtractor 12.
The subtractor 12 subtracts a control signal based on an output signal from the microphone 15,
which will be described later, and the reproduction signal, inputs the output thereof to the power
08-05-2019
5
amplifier 13, and amplifies the power. The signal output from the power amplifier 13 is input to
the speaker 14 and reproduced.
[0017]
A microphone 15 is disposed around the speaker 14, and the microphone 15 collects a
reproduced sound component VM from the speaker 14 and an extraneous noise component VN
around the speaker. An output signal from the microphone 15 is amplified by the microphone
amplifier 16 and negatively fed back to the subtractor 12.
[0018]
Here, the reproduction signal from the signal source 11 is input to one input end of the second
subtractor 21 through the speaker equivalent filter 20, and the output signal of the microphone
amplifier 16 is output from the second subtractor 21. The signal of only the extraneous noise
component VN is extracted from the second subtractor 21 by being input to the other input
terminal and subjected to subtraction processing. A signal derived only from the extraneous
noise component is input to the AC / DC converter 22, subjected to detection and integration
processing, and a control voltage is output from the AC / DC converter 22.
[0019]
The control voltage from the AC / DC converter 22 is applied to a voltage control amplifier 19
provided between the microphone amplifier 16 and the subtractor 12 to control the gain of the
voltage control amplifier 19, thereby performing the subtraction. The magnitude of the output
signal from the microphone amplifier 16 negatively fed back to the unit 12 is changed. On the
other hand, the control voltage from the AC / DC converter 22 is applied to a voltage control
filter 18 provided between the signal source 11 and the subtractor 12 to change the
characteristics of the voltage control filter 18. Therefore, the feedback amount of the feedback
loop from the microphone 15 to the subtractor 12 is changed in conjunction with the external
noise component input to the microphone 15, and at the same time the correction of the
reproduction frequency characteristic to the reproduction signal from the signal source 11 is
automatically performed. Can be done.
08-05-2019
6
[0020]
Specifically, when there is no output of the second subtractor 21, that is, no extraneous noise
component, the gain of the voltage control amplifier 19 is G0 as shown by the solid line in FIG. 4
and the voltage control is made as shown by the solid line in FIG. Assuming that the
characteristics of the filter 18 are determined, the gains of the voltage control amplifier 19 are
G1 and G2 as shown by the broken line and the alternate long and short dash line in FIG. 4 as the
output of the second subtractor 21, ie, the external noise component increases. At this time, the
filter characteristics of the voltage control filter 18 are changed as shown by the broken line and
the alternate long and short dash line in FIG. Here, the filter characteristic of the voltage control
filter 18 has the inverse characteristic of the feedback transfer function of the feedback loop.
[0021]
As described above, according to the present invention, the filter having the filter characteristic
related to the feedback transfer function of the feedback loop from the microphone to the
subtractor is subjected to the characteristic correction of the reproduction frequency for the
reproduction signal from the signal source. With such a configuration, it is possible to suppress
the variation in reproduction frequency characteristics caused by the feedback loop provided to
attenuate the external noise, and to attenuate the influence of the external noise without the
deterioration of the reproduction frequency balance.
08-05-2019
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