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JPH03193000

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DESCRIPTION JPH03193000
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
noise reduction device that reduces noise only by an adaptive filter and a subtracter in a listening
room in which music signals and noise are mixed, for example, a general living room or a car
room. Prior Art Conventionally, there has been a strong demand for enjoying music and the like
in a room with a good S / N ratio. Therefore, as a method of reducing the noise level in a room
such as a general household or a car, it is practiced to equip an interior material or a sound
insulation material in the room. In addition, it is also practiced to surround the engine, which is a
noise source, with a sound insulating material such as metal or concrete. Problems to be solved
by the invention However, in the case of a general household, it is necessary to provide
soundproofing in advance at the time of new construction or at the time of new construction or
remodeling, and requires a large amount of cost. Also, depending on the location conditions, even
if soundproofing measures are taken, noise may be plagued. Similarly, in the passenger
compartment, a considerable amount of sound insulation is required to dampen the noise leveler
such as engine noise considerably, and the weight of the whole vehicle increases, so fuel
consumption type, power weight ratio, torque weight There was a problem that performance
such as ratio became worse. The present invention solves the above-mentioned problems, and by
using an electroacoustic means, it is possible to provide an inexpensive, small and light-weight
silencer that can easily reduce noise and improve S / N. It is the purpose. Means for Solving the
Problem In order to achieve this object, the silencer according to the invention comprises a noise
detector, an error detector, an adaptive filter for adaptively controlling the detected noise signal,
and a music signal from a sound source. It consists of a signal processing circuit to control, an
adder to add the music signal and the output of the adaptive filter, a subtractor to subtract the
output of the signal processing circuit from the output of the error detector, a power amplifier,
and a speaker . Operation With this configuration, the signal detected by the error detector is
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converted to only the noise signal by the subtracter, and this is used as the control signal of the
adaptive filter, whereby the noise signal detected by the noise detector is the noise at the
listening point. Is adapted to reduce the noise, added to the input signal such as the music signal
and reproduced from the speaker, the noise in the room is reduced and the S / N is improved.
Embodiment An embodiment of the present invention will be described with reference to the
drawings. FIG. 1 is a block diagram of a noise suppressor according to an embodiment of the
present invention. In FIG. 1, la and lb are microphones, 2a and 2b are adaptive filters, 3 is an
adder, 4 is a power amplifier, 5 is a speaker, 6 is a subtractor, 7a and 7b are switches, 8 is a
sound source device, 9 is a sound source device. It is a noise source.
The operation of the noise reduction device configured as described above will be described
below. Here, in order to simplify the description, consider the case of muting the engine noise in
the car room. First, the engine is turned off, the switch a is turned off, the switch 7b is turned on,
and the tone generator W8 is operated. This state is shown in FIG. The output signal S7 of the
sound source device 8 passes through the adder 3 and the power amplifier 4 and is reproduced
from the speaker 5. The reproduction signal 55-a from the speaker 5 is converted into an electric
signal 56-a by the microphone 1 b and input to the subtractor 6. On the other hand, the signal S7
is also input to the adaptive filter 2b, and the output S8 is input to the subtractor 6. Then, the
signal S8 is subtracted from the signal 56-a by the subtracter 6 to obtain an output signal 59-a,
whereby the adaptive filter 2b is adaptively controlled. Here, the transfer function of the adder 3
is Had, the transfer function of the power amplifier 4 is Ham, the transfer function of the speaker
5 is Hsp, the transfer function of the microphone 1b is Hm2, the transfer function of the
subtracter 6 is Hsu, and the adaptive filter 2b Assuming that the transfer function is HG2 and the
transfer function between the speaker 5 and the microphone 1b is G511, the signal 56-a is 56-aGs-Hm2-Hsp-Ham-Hac S7. Here, the adaptive filter 2b is adapted to attenuate the signal 59-a. In
other words, signal S8 is controlled to be equal to signal 56-a. That is, in S9-a = Hsu (S6-a-38),
the signal 59-a approaches "0". Therefore, the adaptive filter 2b realizes the following
characteristics. Ha2 ′ ′ Gsm 1 H @ 2 ° Hsp Ham Had Next, the sound source device 8 is
stopped, the switch 7 b is turned off, the switch 7 a is turned on, and the engine is turned on.
This state is shown in FIG. 3. When the noise N1 is detected by the microphone 1a and adjusted
by the adaptive filter 2a, it is reproduced by the speaker 5 through the adder 3 and the power
amplifier 4. On the other hand, the noise N2 is detected at the listening point from the engine
which is the noise source 9. At the same time, the reproduced sound 55-b from any of the
speakers 5 is also detected. Then, the detected signal 56-b passes through the subtracter 6 to
become the control signal 59-b of the adaptive filter 2a. The adaptive filter 2a adapts to
attenuate this control signal 59-b. Here, the transfer function of the microphone 1a is Hml, the
transfer function of the adaptive filter 2a is Hal, the engine sound is N1, the transfer function
between the engine 9 and the microphone 1a is G, the transfer function between the engine 9
and the microphone 1b is Gm2, and Then, the control signal 59-b is S9-h- (Hsp-Ham-Had-Hal-H-H1-Gw1x Gsn ++ Gm2) Hsu-Hm2-N.
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Therefore, since Hsp-Ham-Had-Hal-1 (+ 1.Gm1.Gs +++ Gm2 = 0 is sufficient, the adaptive filter 2a
realizes the following transfer function. Hal-Cd / Hsp-Ham-Had-Hml.Gml-Gsm With this, the noise
N2 at the listening point is canceled by the reproduced sound 55-b from the speaker 5. When the
above adjustment is completed, the sound source device 8 is operated. Then, since 53 = Had (S2
+ S7) is performed in the adder 3, the signal S6 is 56 = HI112 ((Hsp-Has-Had-Hal · Hml · C; 5IIIX
G111 + G52) N + Hsp − Ham · Had − Gsm · S 7). Since the signal S8 is S8 = Hsp-Ham-HadHm2.Gsm-37 from whichever result, the signal S9 is 59 = Hsu (S658) = (Hsp-Ham-Had-HalHml.Gsm -Gml + Gm2) It becomes Hsu-Hm2-N. Since this is the same as any signal 59-b, Hal may
be adapted so that 59 = 0. As a result, it is possible to attenuate only the noise in the car room
where the music signal and the noise are mixed. As described above, according to the present
embodiment, the signal from the sound source device 8 is adaptively controlled by the adaptive
filter 2b, and this is subtracted from the signal at the listening point detected by the subtracter 6
by the microphone 1b. Further, the noise signal detected by the microphone la by this control
signal is adaptively controlled by the adaptive filter 2a and added to the music signal by the
adder 3 to attenuate only the noise signal at the listening point. be able to. Therefore, good sound
of S / N can be enjoyed. In this embodiment, after the adjustment in FIG. 2 is completed, the
switches 7a and 7b are adjusted to be as shown in FIG. 3. However, identification of the adaptive
filter 2b or identification of the final filter 2a may be performed in advance. It is clearer than the
explanation of. Further, the sound source device 8, the power amplifier 4, and the speaker 5 may
use a hand-held device. According to the present invention, only the noise signal can be extracted
by controlling the music signal by the signal processing circuit and subtracting it from the signal
detected by the error detector by the subtractor, and using this control signal, adaptive control is
performed. By controlling the filter, the noise signal detected by the noise detector can be
adapted, and the signal and the music signal can be added by the adder and reproduced to
attenuate only the noise at the listening point.
Thus, the present invention can be realized inexpensively with a simple configuration. Further,
since the feedback from the error detector is used for the control signal of the adaptive filter,
various excellent effects such as stable operation can be obtained.
[0002]
Brief description of the drawings
[0003]
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FIG. 1 is a block diagram of a silencer according to an embodiment of the present invention, FIG.
2 is a block diagram when the switch 7b is closed and the switch 7a is opened in FIG. 1, and FIG.
3 is a switch in FIG. It is a block diagram when opening 7b and closing switch 7a.
la, lb... microphones 2a 2b adaptive filters 3 adders 4 power amplifiers 5. Speaker, 6 .....
Subtractor, 7a. 7b ························································ Noise source.
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