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DESCRIPTION JPH07287934

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DESCRIPTION JPH07287934
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
noise canceller for removing high frequency noise from an audio signal.
[0002]
2. Description of the Related Art For example, as a technique used to reduce noise such as hiss
noise that is noticeable in high frequencies from an audio signal in an analog tape player etc., it is
widely known in Dolby, DBX, address etc. As in the prior art, there are techniques of compressing
a signal at the time of recording, decompressing and outputting at the time of reproduction, and
a technique of using a low pass filter.
[0003]
However, in the Dolby method, DBX method, address method, etc., of course, compression
processing based on that method is performed at the time of recording, and unless recording is
performed, the appropriate effect can not be obtained at the time of reproduction. There is a
problem that the playback device for which the reduction effect is effective is limited by the
system at the time of recording.
[0004]
Also, in the case of using a low pass filter, in order to obtain a sufficient noise reduction effect, it
is necessary to configure a filter of many orders, resulting in an increase in the number of parts
and an increase in hardware size. There is a problem that it can not be easily adopted in various
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sound output devices.
[0005]
SUMMARY OF THE INVENTION In view of such problems, the present invention eliminates the
need for matching with a system at the time of recording by performing noise reduction by
processing only at the time of reproduction, and also simple. An object of the present invention is
to provide a noise canceller that can be realized with a hardware configuration.
[0006]
Therefore, as noise cancellers, sampling means for sampling an input voice signal at
predetermined sample timing, n sample output means for outputting n past sample signals by the
sampling means at each sample timing, and n sample output means And output calculation
means for obtaining an output sound signal from the sum of n sample signals.
[0007]
According to the above configuration, that is, the simple moving average of the input signal is
taken and this is output, that is, the signal component is smoothed according to the setting of the
sample timing and the number of samples for which the simple moving average is taken, It is
possible to obtain an output in which high frequency noise is reduced.
[0008]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A noise canceller according to an
embodiment of the present invention will be described below with reference to FIGS.
This noise canceller is suitable for mounting on, for example, an analog tape player, and is
disposed as shown in FIG. 2 in the analog tape player.
That is, the audio signal extracted by the magnetic head 10 from the tape T on which the audio
signal is recorded is subjected to processing such as reproduction equalization and amplification
by the preamplifier 11. The output of the preamplifier 11 is supplied to the noise canceller 1 of
this embodiment. Be done.
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Then, the audio signal subjected to the noise reduction processing in the noise canceller 1 is
supplied to the power amplifier 12, amplified, and output from the speaker 13 as audio.
[0009]
The noise canceller 1 is configured as shown in FIG.
2 is a sample / hold circuit, 31 to 3 (n-1) are delay circuits, and 4 is a summing amplifier.
A clock CLK of about 48 KHz, for example, is supplied to the sample / hold circuit 2 and the
delay circuits 31 to 3 (n-1), and the sample / hold circuit 2 receives the audio signal SIN with the
clock CLK as sample timing. Sample and hold output.
[0010]
Each of the delay circuits 31 to 3 (n-1) gives a delay time of the clock CLK timing to the input
signal and outputs it, that is, shifts the signal according to the clock CLK, Do the action.
The delay circuits 31 to 3 (n-1) can be configured using, for example, a BBD circuit (bucket
brigate device).
[0011]
The signal S1 which is the output of the sample / hold circuit 2 is input to the delay circuit 31 in
accordance with the clock CLK and is also supplied to the summing amplifier 4, and the signal S2
which is the output of the delay circuits 31 to 3 (n-1). Sn is also supplied to the summing
amplifier 4 together with the delay circuit of the next stage. Therefore, the summing amplifier 4
supplies the past n times of sampled signals (ie, the signals S1 to Sn) from the signal sampled at
each sampling timing by the clock CLK, and the signals S1 to Sn are simple. The average is
obtained, which is taken as the output signal SOUT. For example, in the summing amplifier 4, the
calculation of SOUT = (1 / n) (S1 + S2 + S3.... + Sn) is performed and the signal SOUT is output.
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[0012]
Therefore, in the noise canceller 1, a simple moving average is obtained for the input signal SIN,
and this is used as the output signal SOUT. As shown in FIG. 3, for the input signal SIN containing
the high-frequency noise component, a moving average is taken by the n-sample signal and the
signal is smoothed to obtain the high-frequency signal as the output signal SOUT. The noise
component is considerably reduced, that is, a low pass filter noise canceller can be realized with a
simple configuration.
[0013]
Here, the frequency of the signal to be reduced is determined by the frequency of the clock CLK
and the number of stages of the delay circuit, that is, the number n of samples, and accordingly,
an appropriate design as a noise filter according to the frequency as noise to be reduced. Can be
done easily.
[0014]
The noise cancellation function is not limited to the recording method at the time of recording,
that is, even if it is an audio signal recorded on the magnetic tape T by normal recording without
compression, it is compressed by the Dolby method, DBX method, etc. The noise reduction
operation can be performed well even in the case of an audio signal recorded by performing the
above.
[0015]
In addition to being applied to the tape player as described above, such a noise canceller of the
present invention is suitable for various sound output devices, and is also effective as, for
example, a noise canceller for a listening sound in a telephone or radio receiver.
[0016]
As described above, the noise canceller of the present invention is realized by a very simple
configuration because the simple moving average of the input signal is taken to smooth the
signal so that the noise in the high region is reduced. There is an effect that noise reduction
operation can be realized without being limited to the state of the input voice (for example,
compressed signal / non-compressed signal).
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And by these effects, it will be able to employ | adopt in various apparatuses very versatile.
[0017]
Brief description of the drawings
[0018]
1 is a block diagram of an embodiment of the noise canceller of the present invention.
[0019]
FIG. 3 is a block diagram of a tape player in which the noise canceller of FIG. 2 embodiment is
employed.
[0020]
It is explanatory drawing of the noise reduction operation | movement of the noise canceller of
the FIG. 3 Example.
[0021]
Explanation of sign
[0022]
1 noise canceller 2 sample / hold circuit 31 to 3 (n-1) delay circuit 4 summing amplifier
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