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DESCRIPTION JPH0456499

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DESCRIPTION JPH0456499
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
active noise canceller having a function of actively canceling external noise. (Prior Art)
Conventionally, as an active noise canceller, for example, the one described in US Pat. No.
4,455,65'75 is known. The active noise canceller outputs, from the muffling speaker, cancellation
sound in reverse phase to the input sound from the monitoring microphone, and muffles external
noise by canceling out the external noise and the cancellation sound. However, according to this
prior art, there is a problem that it is difficult to install a monitoring microphone so as to input
the cancellation sound without bias and not to disturb the sound field of the cancellation sound.
In addition, since the monitor microphone needs to receive external noise as well, it needs to be
spaced to a certain extent from the muffling speaker, which causes a phase delay to cause
howling. Therefore, the applicant of the present application has proposed an active noise
canceller (hereinafter referred to as prior art) described in Japanese Patent Application No. 144790 as a means for solving the above conventional problems by means of a simple control
circuit that does not require feedback control. Proposed. In this prior art, the negative pressure
surface of the muffling speaker is provided with a sub-speaker emitting a secondary canceling
sound in the same phase as the canceling sound, and the sound in reverse phase to the canceling
sound radiated from the negative pressure surface of muff The monitor microphone is provided
at a position where the sub-cancellation sound and the sub-cancellation sound cancel each other
so that only external noise is input to the monitor microphone. (Problems to be Solved by the
Invention) In the above-mentioned prior art, when canceling external noise such as noise and the
like, it is necessary to perform 0N-OFF operation of the switch, which is troublesome. In addition,
there is also a problem that power consumption is increased if the cancellation operation is
always performed. The present invention has been made focusing on the problems as described
above, and it is an object of the present invention to develop an active noise canceller which can
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save energy by reducing the amount of power consumption while eliminating the
troublesomeness of switch operation. Do. (Means for Solving the Problems) In the active noise
canceller of the present invention, when the input sound from the monitoring microphone
indicates preset sound information, the cancellation sound generation signal and the sub
cancellation sound generation signal are output. The above problem is solved by providing the
noise cancellation circuit with a condition setting circuit that prohibits the operation and can not
output the set sound information when the set sound information is not obtained.
That is, in the active noise canceller according to the present invention, the muffling speaker
which radiates a predetermined canceling sound from the positive or negative surface toward the
muffling target space, and the same canceling sound toward the other surface of the muffling
speaker The sub-speaker that radiates the sub-cancellation sound of the phase, the monitor
microphone disposed at the position where the sound radiated from both speakers cancel each
other, and the cancellation sound of the opposite phase to the input sound from the monitor
microphone Output a cancellation sound generation signal for emission from one of the faces,
and output a sub cancellation sound generation signal for emission of a sub cancellation sound in
phase with the cancellation sound from the sub speaker to the other surface of the muffling
speaker And a noise cancellation circuit, provided in the noise cancellation circuit, from the
monitoring microphone. Allows the operation to output the cancellation sound generation signal
and the secondary cancellation sound generation signal when the heavy noise indicates preset
sound information, and prohibits the output of both generation signals when the set sound
information can not be obtained. And a condition setting circuit. (Operation) When muffling is
performed, the cancellation sound is emitted from the muffling speaker toward the muffling
target space based on the sound input from the monitoring microphone. Therefore, in the noise
reduction target space, the extraneous sound is canceled by the cancellation sound of the
opposite phase. Also, the monitoring microphone is disposed at a position where the sound from
both speakers is canceled, that is, at this position, the cancellation sound emitted from the
positive and negative sides of the muffling speaker and the other side are emitted Negative
cancellation sound in opposite phase to the cancellation sound and negative cancellation sound
in opposite phase to the cancellation sound emitted from the positive and negative sides of the
auxiliary speaker respectively (negative canceler) and auxiliary cancellation sound (= cancellation
sound) The sound from both speakers is not input, and only the external sound can be input. By
the way, in the present invention, the muting of the extraneous sound as described above is
performed when the extraneous sound input from the monitor microphone indicates the set
sound information in the condition setting circuit. That is, the sound pressure of the foreign
sound is higher than the setting, the frequency of the foreign sound is higher than the set
frequency, conversely, less than the set frequency, the width of the set frequency, or the set
waveform. In the noise cancellation circuit, the above-described cancellation sound generation
signal and the secondary cancellation sound generation signal are output. As described above,
when the input sound from the monitoring microphone does not indicate the set sound
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information, the noise cancellation circuit does not operate to output both generation signals,
and in this case, power is not consumed.
Moreover, the 0N-OFF operation of the device is unnecessary. An embodiment of the present
invention will be described below with reference to the drawings. More, explain the
configuration. FIG. 1 is an overall view showing a configuration of an active noise canceller
according to an embodiment of the present invention, in which 1 is a noise reduction speaker for
generating and emitting a predetermined cancellation sound to a user's ear cavity E; Sub-speaker,
3 is a monitor microphone for inputting the external sound A, 4 is a noise cancellation circuit for
outputting the cancellation sound generation signal a to the muffling speaker 1, and outputting a
sub-cancellation sound generation signal to the sub-speaker 2, 5 Is a partition, 6 is a cover. The
muffling speaker 1 is provided with a diaphragm Ib, a coil Ic and a magnet 1d. When the coil 1c
is energized, it is attracted to the magnet 1d and vibrates the diaphragm 1b. The diaphragm
surface 1e is a positive pressure surface. The back surface 1 f is a negative pressure surface. The
sub-speaker 2 is the same speaker as the muffling speaker 1, that is, an acoustically equivalent
speaker including a diaphragm 2b, a coil 2c and a magnet 2d, and the diaphragm surface 2e is a
positive pressure surface, and the diaphragm The back surface 2f is a negative pressure surface.
The partition 5 defines the inside of the headphone-like cover 6 into a noise reduction space B
and an extraneous sound side space C, and supports both the speakers 1.2. The support structure
supports the two speakers 1.2 symmetrically at the center of the partition 5 and forms an
intermediate chamber between the two speakers 1 and 2. Further, in the partition wall 5, a
communication hole 5a communicating the intermediate chamber and the extraneous sound side
space C is formed. The monitoring microphone 3 is attached to a mounting hole 5b formed in the
partition wall 5 at a lower position between the two speakers 1.2. The monitor microphone 3 and
the two speakers 1.2 are connected to the noise cancellation circuit 4. That is, the noise
cancellation circuit 4 causes the both speakers 1 and 2 to emit the cancellation sound 81 and the
auxiliary cancellation sound s2 based on the sound input from the monitoring microphone 3, and
the preamplifier 4c and the condition setting circuit 4a. , Filter circuit 4d. It has a power amplifier
4e and an inverting circuit 4f. The preamplifier 4c receives the signal from the monitor
microphone 3 and pre-amplifies this input signal. The filter circuit 4d removes an unnecessary
frequency range from the cancellation sound from the signal passing through the preamplifier 4c
obtained through the condition setting circuit 4 days, that is, can not be output from both the
speakers 1 and 2 It is configured to remove sound in the frequency range.
The power amplifier 4e mainly amplifies the signal that has passed through the filter circuit 4d
so that the sound pressure of the cancellation sound s1, which will be described later, becomes
equal to the external sound A. The inverting circuit 4 f is a circuit that shifts the phase of the
signal from the power amplifier 4 c by 180 degrees and outputs it to the muffling speaker 1. The
condition setting circuit 4a passes this signal to the filter circuit 4d when the sound pressure of
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the input sound indicated by the signal passed through the preamplifier 4c is equal to or higher
than a predetermined level, and cuts the signal when the sound pressure is lower than the
predetermined level. It is. The configuration of this condition setting circuit is shown in the
circuit diagram of FIG. 2. The symbols of (1) and (2) correspond to FIG. In part, the condition
setting circuit 4a includes operational amplifiers 41.42 and 43. And the relay switch 45 which is
normally open, and as shown in FIG. 3, when the sound pressure level of the input signal 9
obtained through the preamplifier 4c is less than the set level 1, the relay switch 45 is used. Is
open and the signal from the preamplifier 4c is cut off. Then, as shown in FIG. 4, when the sound
pressure level of the human power signal 9 exceeds the set level h, the relay switch 45 is closed
and the input signal 9 is passed to the filter circuit 4d side. A cancellation sound generation
signal a and a secondary cancellation sound generation signal are formed. Next, the operation
will be described. For example, when it is desired to prevent the external noise from being heard
under the external noise of a factory or the like where intermittent noise is generated, the
apparatus of this embodiment is applied to the ear cavity E as shown in the drawing. The
operation at this time will be briefly described. First, external noise (external noise) A is input to
the monitoring microphone 3, converted to an electric signal, and input to the noise cancellation
circuit 4. Then, after this signal is preamplified by the preamplifier 4c, it is judged in the
condition setting circuit 4a whether the sound pressure level of the input signal 9 is the set level
1 or higher, and the sound pressure level exceeds the sound level h. Is transmitted to the side of
the filter circuit 4d. As described above, when the signal is transmitted to the filter circuit 4d
side, this signal is subjected to amplification and filter processing, and a cancellation sound is
generated which is a signal obtained by inverting the phase of the external sound A with respect
to the muffling speaker 1 A signal a is output, while an auxiliary cancellation sound generation
signal which is a signal in the same phase as the extraneous sound A is output to the auxiliary
speaker 2. Therefore, from the muffling speaker 1, the cancellation sound s1 of the opposite
phase to the foreign sound A is emitted toward the muffling space B, and on this muffling space
day, the foreign sound A cancels the canceling action by the cancellation sound s1 of this
opposite phase. Received and muted.
Then, when generation of a loud noise such that the sound pressure level of the input signal 9
exceeds the set level h stops, the relay switch 44 of the condition setting circuit 4a is opened to
shut off the input signal 9, and a cancellation sound generation signal The generation of the a
and the secondary cancellation sound generation signal is stopped. Therefore, since it is not
under the loud noise and the cancellation operation is not performed, the conversation etc. can
be performed. By the way, when the cancellation sound $ 1 is emitted from the muffling speaker
1, a negative cancellation sound t1 having a phase opposite to that of the cancellation sound s1
is emitted from the diaphragm back surface 1f which is the negative pressure surface. On the
other hand, the sub-speaker 2 is supplied with a sub-cancel sound generation signal in reverse
phase to the cancel sound generation signal a, that is, from the diaphragm back surface 2 f
toward the muffling speaker 1 The cancellation sound s2 is emitted, and the negative
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cancellation table t2 (= negative cancellation sound t1) having a phase opposite to that of the
auxiliary cancellation sound s1 (= cancellation sound s2) is emitted from the diaphragm surface
2e toward the extraneous sound side space C. Ru. Accordingly, in the middle room between the
two speakers 1.2, the negative cancellation sound t1 emitted from the muffling speaker 1 and the
auxiliary cancellation sound s2 emitted from the auxiliary speaker 2 are canceled out by the
opposite phase, so that In the monitor microphone 3, the sounds from both the speakers 1 and 2
are not input, and only the external sound A can be input. As mentioned above, although an
Example was described based on a drawing, a concrete composition is not given to this example.
For example, in the embodiment, the sound pressure of the input sound is indicated as the sound
information set in advance in the condition setting circuit, but the frequency or waveform of the
sound may be set. That is, when only certain high-pitched noises and low-pitched noises are
muted, and intermediate frequencies such as conversational sounds are not desired to be erased,
a bypass filter, low-pass filter, etc. are provided in the condition setting circuit. Only when the
signal passes, the signal may be passed to form the cancellation sound generation signal and the
secondary cancellation sound generation signal. Further, when only a predetermined sound is
desired to be muted, the waveform may be set, and the signal may be allowed to pass only when
the signal of the waveform is input. In the example, the positive pressure surfaces 1e and 2e of
the diaphragms + b and 2b of both speakers 1.2 are arranged toward the noise reduction target
space B and the extraneous sound side space C, but they are rotated by 180 ░ and negative The
pressure surfaces 1f and 2f may be directed in the direction thereof.
(Effects of the Invention) As described above, in the Acty 7 noise canceller of the present
invention, when the input sound from the monitoring microphone indicates preset sound
information, the cancellation sound generation signal and the auxiliary sound are generated.
Since the noise cancellation circuit is provided with a condition setting circuit that prohibits the
output of the both generation signals when it is possible to output the cancellation sound
generation signal and the set sound information can not be obtained, the noise cancellation
circuit When performing the mute operation to output the cancellation sound generation signal
and the secondary cancellation sound generation signal, the sound generation operation is
automatically performed when the sound to be extinguished is input without performing the ON
/ OFF operation, and operated otherwise. Since it is stopped, there is no bother of ON и ? FF
operation, and unnecessary power consumption can not be achieved, and energy saving can be
achieved. Obtained.
[0002]
Brief description of the drawings
[0003]
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Fig. 1 is a general view showing the structure of the Acty 7 noise canceller of the embodiment of
the present invention, Fig. 2 is a circuit diagram showing the main part of the embodiment, and
Figs. 3 and 4 are input sound levels and set levels It is Kura 7 showing the relation with.
1 ... muffling speaker 1e ... diaphragm surface (positive pressure surface) 1f --- diaphragm back
surface (negative pressure surface) 2 ... secondary speaker 3 ... monitoring microphone 4 ... noise
cancellation circuit 4 days ... и Condition setting circuit a и и и Cancel sound generation signal b и и и и
secondary cancellation sound generation signal sl и и и и и Cancel sound s 2 иии Secondary
cancellation sound Fig. 2 41.42.43 и и и Op amp 44 Transistor 45 иии relays inch
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