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JPH0550495

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DESCRIPTION JPH0550495
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
silencer based on the principle of active silencer.
[0002]
2. Description of the Related Art As one of the noise reduction devices, there is an active noise
reduction device which adds a sound (interference sound) of opposite phase to noise and makes
noise reduction by an interference effect.
[0003]
As one mode of this active noise cancellation, there is an adaptive active noise cancellation that
detects an actually generated noise and generates an interference sound of the opposite phase.
[0004]
As another active noise reduction method, when the noise source is operated intermittently, the
noise generated by the noise source is stored in advance in the storage device, and when the
noise source is activated, the noise is reverse to the stored sound. There is also considered a
silencer that generates a phase interference sound.
[0005]
According to the active muffling apparatus, although the front area (the arrival area of the
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interference sound wave) of the speaker that outputs the interference sound can be muffled
efficiently, the arrival area of the interference sound wave can be obtained. There is a problem
that the muffling effect becomes extremely poor.
[0006]
If many active silencers are installed, such problems can be solved, but the equipment cost
becomes extremely high.
[0007]
SUMMARY OF THE INVENTION An active noise reduction system according to the present
invention comprises an interference sound generation circuit for generating an interference
sound in the opposite phase of noise and an interference sound upon receiving an output from
the interference sound generation circuit. An active muffling apparatus having a speaker for
generating a human body, comprising: a human body detection sensor for detecting a human
body position; and an attitude changing device for directing the speaker to the detected human
body position.
[0008]
In the active noise reduction device of the present invention, since the direction of the speaker is
changed to point to the human body, the ear of the human body can be spread over a wide range
without increasing the number of devices. The interference noise can be supplied to the active
noise cancellation.
[0009]
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram of an active silencer according to the embodiment, and FIG. 2 is a
perspective view of a bathroom provided with the active silencer.
[0010]
In FIG. 2, the bath 31 is provided with a bubble jet nozzle 32.
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Hot water in the bathtub 31 is circulated and supplied to the bubble jet nozzle 32 through a
pump.
Then, air is supplied so as to be sucked into the jet flow at the portion of the nozzle 32, and a
gas-liquid mixed jet is jetted from the nozzle 32 into the bath 31.
[0011]
At the time of the bubble spouting operation, in addition to the spouting noise from the nozzle
32, noise such as bubble bubbling noise or pump operation noise reaches the bather's ear.
[0012]
Therefore, in order to actively mute the noise, a speaker 9 is installed on the flange portion of the
bath 31 and configured to output a interference sound upon receiving a signal from the
interference sound generation circuit.
[0013]
As shown in FIG. 1, this interference sound generation circuit is provided with a microphone 1
for noise collection, a speaker 9 for interference sound output, an evaluation microphone 10 and
a human body detection sensor 16.
[0014]
As shown in FIG. 1, in this interference sound generation circuit, the detection sound of the
microphone 1 is taken in via the selection circuit 2 described later, amplified by the amplifier 3,
and then passed through the low pass filter (LPF) 4. Select only low frequency sound signals in
the audible band.
The low frequency sound signal is A / D converted by the A / D converter 5, and the phase
inverted signal is generated by the digital filter (DF) 6.
This inverted signal is D / A converted by the D / A converter 7 and then amplified by the
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amplifier 8 to produce a sound from the speaker 9.
The sound output to the speaker 9 is a sound detected by the microphone 1 or an interference
sound in reverse phase to the sound currently being detected, and the active noise reduction is
performed.
[0015]
In this embodiment, the adaptive active noise reduction is also used, and the adaptive active
noise reduction microphone (evaluation microphone) 10 is provided, and the adaptive active
noise reduction amplifier 12, the low-pass filter 13, the A / D. A converter 14 and an adaptive
controller 15 are provided.
The sound detected by the evaluation microphone 10 is taken in via the selection circuit 11
described later.
This sound is amplified, passes through a low pass filter (LPF) 13, is A / D converted, and is input
to the adaptive controller 15.
The adaptive controller 15 determines whether the muffling action is sufficiently exhibited, sends
a control signal to the digital filter (DF) 6 or the amplifier 8, optimizes the phase of the inverted
signal and the sound pressure of the inverted sound, and is sufficient. Mute.
[0016]
The speaker 9 is attitude controlled so as to always face the human body.
In order to specify the human body position, as shown in FIG. 2, a plurality of human body
detection sensors 35, 36 are provided on the wall surfaces 33, 34 respectively. Each sensor 35,
36 detects a human body in front of it. Since the sensor 35 of the wall surface 33 and the sensor
36 of the wall surface 34 are XY-arranged, the position of the human body in the bath 31 can be
specified.
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[0017]
The detection signals of the sensors 35 and 36 are input to a human body position detection
circuit 37 for specifying the XY position of the human body. The human body position detection
circuit 37 outputs control signals to the select circuits 2 and 11 and a motor drive circuit 38 to
be described next. The motor drive circuit 38 is for controlling a motor 39 for rotating the
speaker 9. The motor 39 is disposed below the flange portion of the bath 31 and rotates the
speaker 9 around a vertical axis.
[0018]
The microphones 1 and 10 are provided for each of the sensors 35 and 36. That is, one sound
collecting microphone 1 and one evaluation microphone 10 are disposed so as to form one set
for each sensor 35 or 36. The select circuits 2 and 11 transmit to the amplifiers 3 and 12
detection sounds of those of the microphones 1 and 10 of which the human body is detected in
front of the microphones 1 and 10 according to a signal from the human body position detection
circuit 37.
[0019]
In the active muffling apparatus configured as described above, the speaker 9 is subjected to
attitude control by the motor 39 so as to always face the human body in the bathtub 31. Then,
the sound in the vicinity of the human body is collected by the microphone 1, and the
interference sound of the opposite phase is output from the speaker 9. In addition, the active
muffling situation in the vicinity of the human body is detected by the evaluation microphone 10
and adaptively muffled.
[0020]
As a result, regardless of the position of the bather in the bath 31, an interference sound of a
sufficient volume can be supplied to the bather's ear, and the active noise cancellation can be
reliably performed.
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[0021]
Since the microphones 1 and 10 having no human body ahead are not operated, the frequency of
operation of the microphones is reduced, and the durability thereof is improved.
[0022]
Of course, since there is only one interference sound generation circuit as a whole, the
equipment cost is low.
When a plurality of human body detection sensors 35 or 36 simultaneously detect a human
body, the sum of the detection sounds of the microphone 1 close to each sensor 35 or 36 is
treated as noise, and the antiphase sound to this sum is output as interference sound Just do it.
[0023]
In the above embodiment, adaptive active noise reduction is performed. However, in the present
invention, noise data may be stored in a memory in advance, and interference noise may be
output based on the stored data.
[0024]
Further, in the present invention, the active muffling operation may be performed only when the
sound pressure level of the detection sound of the microphone 1 becomes equal to or more than
the threshold value.
In this way, the frequency of operation of the speaker or the like is reduced, and its durability is
improved.
[0025]
In the above embodiment, the vicinity of the ear of the human body in the bathtub 21 is actively
muffled by the speaker 9, but the rotation range of the speaker may be extended so as to muffle
the washing place 40.
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In addition, the speaker may be rotated in the vertical direction. The number of installed speakers
may be one or three or more.
[0026]
It is obvious that the installation position of the speaker may be a position other than that shown.
[0027]
Although the above embodiment relates to the noise reduction device for a bathroom, the present
invention can be applied to various rooms such as a living room, a kitchen, a toilet room, an
office room and the like.
[0028]
As described above, according to the active noise reduction device of the present invention, even
if the human body moves, the direction of the speaker can be changed accordingly and
interference sound can be supplied to the ear of the human body, which is certain. Can be
actively muted.
In addition, since the number of speakers can be small and a plurality of microphones are
connected to a common interference sound generation circuit, the equipment cost is low.
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