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DESCRIPTION JPH03113888

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DESCRIPTION JPH03113888
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
noise reduction device for a magnetic recording and reproducing apparatus, and more
particularly to a noise reduction device capable of realizing a stable noise reduction effect. 2.
Description of the Related Art FIGS. 5 and 6 show a conventional magnetic recording and
reproducing apparatus, showing a state in which a rotary head of a helical scan type VTR
transports while scanning a tape. In these figures, 1 is a magnetic head, 2 is a rotary drum, 3 is a
magnetic tape, 4 is a guide pin for guiding the magnetic tape 3 in its width direction, and 5 is a
fixed head. Reference numeral 6 denotes a capstan motor, which pinches and rotates the
magnetic tape 3 together with the pinch roller 7 to pull and transfer the magnetic tape.
Reference numeral 8 is a tape guiding drum for guiding the tape 3. Next, the operation will be
described. The magnetic head 1 installed on the rotary drum 2 scans the magnetic tape 3 at high
speed along with the rotary drum 2 rotating at high speed. At this time, the magnetic tape 3 is
wound around the tape guiding drum 8 by an angle by the guide boss 4 and is wound with an
appropriate tension to obtain stable contact between the magnetic tape 3 and the magnetic head
1. There is. Further, since the magnetic shield 1 contacts the magnetic tape 3 to exchange
signals, the magnetic shield 1 protrudes by several tens of micrometers from the outer periphery
of the rotary drum 2. Accordingly, at the tape guiding drum inlet 10 shown in FIG. 4, the
magnetic head 1 makes an impact contact with the magnetic tape 3 to excite vibration. Similarly,
at the tape guide drum outlet 11, the magnetic head 1 is excited at a high speed from the contact
with the magnetic tape 3 to excite vibration. Since the rotary drum 2 generally rotates at a
constant rotational speed, these vibrations become periodic noise and propagate in the air.
[Problems to be Solved by the Invention] Since the conventional magnetic recording and
reproducing apparatus is configured as described above, the generation of noise due to the
separation of the magnetic tape and the magnetic head can not be avoided, and this noise is
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output to the outside. There are problems such as poor heat dissipation to make it difficult, a
sealed exterior structure must be taken, and it is necessary to use an expensive material with
high damping effect as the exterior material. The present invention has been made to solve the
above problems, and provides a noise reduction device of a magnetic recording and reproducing
apparatus capable of largely attenuating the periodic noise generated due to the separation of
the magnetic tape and the magnetic head. The purpose is [Means for Solving the Problems] The
noise reduction device of the magnetic recording and reproducing apparatus according to the
present invention comprises means for converting periodic noise into an electric signal, means
for inverting the phase of the electric signal, and the inversion signal. Means for amplifying the
electric signal and sound generation means for converting the amplified electric signal into
sound.
[Operation] In the present invention, since the periodic noise is converted into an electric signal,
and the phase of the electric signal is inverted and amplified as a sound, the noise is canceled by
the sound whose phase is inverted. Noise can be reduced. Embodiments of the present invention
will be described hereinbelow with reference to the drawings. FIG. 1 is a view showing a noise
reduction device of a magnetic recording and reproducing apparatus according to a first
embodiment of the present invention. In the figure, the same reference numerals as in FIG. 6
denote the same or corresponding parts. Further, 21 is a microphone for converting noise into an
electric signal, 22 is a phase inverting circuit for inverting the phase of the electric signal from
the microphone 21, 23 is an amplifier for amplifying a signal whose phase is inverted, 24 is an
electric signal output from the amplifier Is a speaker that converts sound into sound. Next, the
operation will be described. As described in the conventional example, in the tape guide drum
population 10, the magnetic head 1 vibrates due to the contact with the magnetic tape 3 in an
impulsive manner, and at the tape guide drum outlet 11 the magnetic head l contacts the
magnetic tape 3 The vibrations are caused by the high-speed separation from the air, and these
vibrations propagate as periodic noises into the air. The microphone 21 converts the noise
generated by the separation of the magnetic tape 3 and the magnetic head 1 into an electrical
signal as shown in FIG. 2, and the phase reversal circuit 22 inverts the phase of the electrical
signal due to the noise. The amplifier 23 amplifies this phase-inverted signal, and the speaker 24
converts it into sound. Therefore, as shown in FIG. 2, the sound from the speaker 24 acts to
offset periodic noise, and the synthesized sound becomes small except for the non-periodic
component of the noise source. Thus, in the embodiment of the first brother 1, after the periodic
noise ヲ microphone 21 converts it into an electric signal, the phase of the electric signal is
inverted by the phase inverting circuit 22, and then it is amplified by the amplifier 23 and the
amplified electric signal Is output as a sound by the speaker 24. Therefore, the noise can be
canceled by the sound whose phase is reversed to reduce the noise. By the way, since the noise
reduction device of the first embodiment is configured as described above, the amplitude of the
sound generated by inverting the phase does not necessarily coincide with the amplitude of the
noise (in the phase inverted sound If the amplitude is smaller than the amplitude of the noise, the
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original noise can not be canceled out and a sufficient effect can not be obtained. If the amplitude
of the sound whose phase is reversed is larger than the amplitude of the noise, the sound whose
phase is reversed becomes the new noise. It will
Also, even if the amplification factor of the amplifier is first adjusted to the optimum, the
amplitude of the noise changes significantly with the ambient temperature and humidity and
further with the passage of time, so it is difficult to maintain the noise reduction effect. FIG. 3 is a
view showing a noise reduction apparatus according to a second embodiment of the present
invention which solves the above-mentioned problems. In the figure, the same reference
numerals as FIG. 1 denote the same or corresponding parts. Further, 31 is a microphone for
converting a synthetic sound of noise and a sound obtained by inverting the phase of the noise
into an electric signal, 32 is a quantization circuit for quantizing the amplitude of the electric
signal of the synthetic sound, and 33 is for taking this quantization information. Controller for
changing the amplification factor of an amplifier for amplifying a signal whose phase is inverted
based on this information, 34 is an amplifier for amplifying a signal whose phase is inverted, the
amplifier 34 is an instruction from the controller 33 Can change the amplification factor. Next,
the operation will be described. The microphone 31 converts the synthetic sound of the noise
and the sound obtained by inverting the phase of the noise into an electrical signal. Is sent to the
controller 33 by quantizing this signal. Here, the case where the amplitude of the noise is larger
than the phase-inverted sound as shown in 35. 36a of FIG. 4 will be described. The controller 33
instructs the amplifier 34 to reduce the amplification factor. At this time, however, as shown in
FIG. 4, since the sound 37a whose phase is reversed becomes small, the noise can not be
canceled out and the amplitude of the synthetic sound becomes large as shown in 37b. It is
recognized that the synthetic sound has become large. Then, the controller 33 instructs the
amplifier 34 to increase the amplification factor. As a result, as shown in FIG. 38a, the amplitude
of the inverted waveform increases, so that the amplitude of the synthesized sound decreases as
shown in FIG. The amplitude of the inverted sound exceeds the amplitude of the noise, and the
amplitude of the synthesized sound is increased. At this time, the control device 33 recognizes
the inflection point of this change as the optimum value and maintains this amplification factor.
This minimizes the amplitude of the synthetic sound waveform as shown in FIG. 4b. Thereafter,
when the amplitude of the noise changes for some reason and the amplitude of the synthesized
sound increases, the same operation is repeated to maintain the optimum amplification factor.
Conversely, when the amplitude of the noise is smaller than the phase-inverted sound, the same
operation as above is performed to maintain the optimum value of the amplification factor. Thus,
the amplitude of the noise and the phase of the noise inverted is controlled to about the same
level, and the synthesized sound is maintained at the minimum level.
As described above, in the embodiment of the pen 2, the amplitude of the synthetic sound of the
noise and the sound whose phase is inverted is quantized, and the amplification factor of the
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amplifier for amplifying the signal whose phase is taken into the control device is amplified. By
making this control unit change the amplification factor as variable, the control unit changes the
amplification factor and at the same time reads the quantization information of the synthetic
speech's amplitude while the synthetic speech's amplitude becomes the smallest. The
amplification factor can be obtained so that the noise can always be canceled out by the phasereversed sound. In the above embodiment, the noise to be reduced is described as the periodic
noise generated due to the separation between the magnetic head of the helical scan type
magnetic recording and reproducing apparatus and the magnetic tape, but the noise generation
source to be reduced is the periodicity. The same effect can be obtained for periodic noise
generated by cogging or the like during rotation of the motor, noise of a brush, or a gear device
rotating at a constant number of revolutions, for example. As described above, according to the
present invention, the means for converting periodic noise into an electric signal, the means for
inverting the phase of the electric signal, the means for amplifying the inverted signal, and the
amplification Since the configuration is provided with the sound generation means for converting
the electric signal into the sound, there is an effect that the noise can be offset by the sound
whose phase is reversed to reduce the noise. Furthermore, in the case of controlling the
amplification factor of the sound whose phase of the noise has been inverted to control the
synthetic sound to be the smallest (if it is controlled to be the smallest, even if the noise
amplitude initially varies, the amplification factor is individually optimized. The noise reduction
effect is most effectively obtained, and the synthetic sound is always suppressed to the lowest
level even when the amplification of the noise changes with the passage of time or temperature
humidity, and a stable noise reduction effect is obtained. Have the effect of
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a diagram showing the configuration of the noise reduction device of the magnetic
recording and reproducing apparatus according to the first embodiment of the present invention,
FIG. 2 is a diagram for explaining the operation of the device of FIG. The figure which shows the
structure of the noise reduction apparatus of the magnetic recording and reproducing apparatus
by 2nd Example of invention, FIG. 4 is a wave form diagram for demonstrating operation |
movement of the apparatus of FIG. 3, FIG.
FIG. 6 is a view for explaining the noise generation mechanism of the magnetic recording and
reproducing apparatus. 1 is a magnetic head, 2 is a rotating drum, 3 is a magnetic tape, 4 is a
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guide pin, 21 is a microphone, 22 is a phase inversion circuit, 24 is a speaker, 32 is a
quantization circuit, 33 is a control device, 34 is variable amplification factor amplifier. In the
drawings, the same reference numerals denote the same or corresponding parts.
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