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DESCRIPTION JPH07181988

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DESCRIPTION JPH07181988
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
echo apparatus suitable for a so-called karaoke system etc. More specifically, digital signal
processing is applied to an audio signal from a microphone to generate an echo component, and
this echo component is The present invention relates to an echo apparatus that mixes and
outputs an audio signal from a microphone.
[0002]
2. Description of the Related Art FIG. 4 is a block diagram showing a schematic configuration of a
conventional echo apparatus. In the figure, 1 is a microphone connected to the echo apparatus
main body by wire or wirelessly, 2 is a voice from the microphone 1 Amplifier for amplifying the
signal, 3 is a band pass filter for passing only a predetermined band of the audio signal from the
amplifier 2, 4 is an echo digital signal processing circuit for generating an echo component of the
audio signal from the band pass filter 3 (DSP And 5 are mixing amplifiers for mixing the audio
signal from the band pass filter 3 and the echo component from the echo digital signal
processing circuit 4, and 6 is an amplifier for amplifying and outputting the audio signal from the
mixing amplifier 5.
[0003]
In such an echo device, the audio signal from the microphone 1 is amplified by the amplifier 2
and supplied to the echo digital signal processing circuit 4 through the band pass filter 3 and to
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the mixing amplifier 5.
The echo digital signal processing circuit 4 incorporating an A / D and D / A converter performs
digital signal processing such as delay processing by converting the input audio signal into a
digital signal and writing the digital signal in the built-in RAM. The echo component is generated
and output as an analog echo component. Examples of the echo digital signal processing circuit 4
include YSS 205 manufactured by Yamaha. The echo component from the echo digital signal
processing circuit 4 and the audio signal from the band pass filter 3 are mixed by the mixing
amplifier 5, amplified by the amplifier 6, and output.
[0004]
As described above, the echo digital signal processing circuit 4 is generally composed of a CMOS,
and the power supply voltage is a single power supply of + VDD. The signal that can be input to 4
is limited to 1/2 VDD (peak to peak).
[0005]
Therefore, the gain of the amplifier 2 at the front stage of the echo digital signal processing
circuit 4 is determined by the input sensitivity of the microphone 1 and the echo digital signal
processing circuit 4, and the dynamic range of the audio signal from the microphone 1 is limited.
The audio signal is saturated and distorted at the input of the echo digital signal processing
circuit 4 due to the variation of the input sensitivity of the microphone 1, and the generated echo
component is also distorted and the final output is also distorted. There is a drawback that
[0006]
The present invention has been made in view of the above-described points, and its object is to
improve the performance of an echo apparatus by increasing the dynamic range of an audio
signal.
[0007]
In order to achieve the above-mentioned object, the present invention is configured as follows.
[0008]
That is, the present invention is an echo apparatus comprising: a digital signal processing circuit
that generates an echo component of an audio signal from a microphone; and a mixing circuit
that mixes the echo component from the digital signal processing circuit with an audio signal
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from the microphone And a compression circuit for compressing the level of the audio signal
from the microphone on the front stage side of the digital signal processing circuit, and the level
of the audio signal corresponding to the compression on the rear stage side of the digital signal
processing circuit. An expanding circuit is provided.
[0009]
According to the present invention having the above configuration, the level of the audio signal is
compressed at the front stage of the digital signal processing circuit, and the compressed audio
signal is expanded at the rear stage of the digital signal processing circuit. As a result, it is
possible to improve the saturation and distortion of the audio signal input to the digital signal
processing circuit.
[0010]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present
invention will be described in detail below with reference to the drawings.
[0011]
FIG. 1 is a block diagram of an embodiment of the present invention, and portions corresponding
to the conventional example of FIG. 4 are denoted by the same reference numerals.
[0012]
In the figure, 1 is a microphone connected to the echo apparatus main body by wire or
wirelessly, 2 is an amplifier for amplifying an audio signal from the microphone 1, 3 is a band
pass filter for passing only a predetermined band of the amplified audio signal. , 4 is an echo
digital signal processing circuit (DSP) for generating an echo component of the audio signal from
the band pass filter 3; 5 is an audio signal from the band pass filter 3 and an echo component
from the echo digital signal processing circuit 4; A mixing amplifier for mixing and an amplifier 6
for amplifying and outputting an audio signal, and the above configuration is the same as that of
the conventional example.
[0013]
In this embodiment, in order to increase the dynamic range of the audio signal from the
microphone 1 to improve the performance of the echo device, the level of the audio signal from
the amplifier 2 is compressed in the previous stage of the echo digital signal processing circuit 4
A square root circuit 7 for outputting to the echo digital signal processing circuit 4 and the
mixing amplifier 5 through the band pass filter 3 is provided, and the level of the mixed audio
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signal is provided in the subsequent stage of the mixing amplifier 5 in accordance with the
compression. An expanding squaring circuit 8 is provided.
[0014]
The square root circuit (square unit) 7 and the square circuit 8 have input / output
characteristics shown by solid lines and broken lines in FIG. 2, respectively, and are
conventionally known circuits.
[0015]
In the echo apparatus having the above configuration, the audio signal from the microphone 1 is
amplified by the amplifier 7 and its level is compressed by the square root circuit 7.
For example, if the audio signal from the microphone 1 is 2 V, it is compressed to 1.41 V by the
square root circuit 7.
The audio signal compressed by the square root circuit 7 is applied to the echo digital signal
processing circuit 4 through the band pass filter 3 and to the mixing amplifier 5.
[0016]
The echo digital signal processing circuit 4 converts the input audio signal into a digital signal,
writes the digital signal in the built-in RAM, performs digital signal processing such as delay
processing by reading, generates an echo component, and generates an analog echo component.
Output as
Assuming that the power supply voltage VDD of the echo digital signal processing circuit 4 is, for
example, +5 V, the signal level that can be input to the echo digital signal processing circuit 4 is
1/2 VDD (peak to peak), and at most 2. It becomes 5Vp-p.
Therefore, up to about 6.25 Vp-p (= 2.52) at the input of the square root circuit 7 will be
acceptable.
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This makes it possible to increase the dynamic range by about 2.5 times as compared with the
conventional echo device.
[0017]
The echo component from the echo digital signal processing circuit 4 is mixed with the audio
signal from the band pass filter 3 by the mixing amplifier 5, squared by the squaring circuit 8
and restored, amplified by the amplifier 6 and outputted. Ru.
[0018]
As described above, the level of the audio signal is compressed by the square root circuit 7 and
input to the digital signal processing circuit 4 for echo, and the echo component generated by
the digital signal processing circuit 4 for echo and the audio signal are mixed. Since the signal is
expanded by 8, the signal level that can be input to the square root circuit 7 is increased, the
dynamic range is increased compared to the conventional example, and the voice is input to the
input of the echo digital signal processing circuit 4 as in the conventional example. It is
prevented that the signal is saturated and distorted.
[0019]
In the embodiment described above, the audio signal to the echo digital signal processing circuit
4 and the mixing amplifier 5 is compressed, and the audio signal mixed by the mixing amplifier 5
is expanded, but as another embodiment of the present invention As shown in FIG. 3, only the
audio signal input to the echo digital signal processing circuit 4 is compressed by the square root
circuit 7, and only the echo component output from the echo digital signal processing circuit 4 is
squared circuit 8 It may be extended by
[0020]
In the above embodiment, although the square root circuit is compressed and the square circuit
is expanded, the present invention is not limited to the square root circuit and the square circuit,
for example, logarithmic compression and expansion Good.
[0021]
As described above, according to the present invention, the level of the audio signal is
compressed at the front stage of the digital signal processing circuit that generates the echo
component, and the compressed audio signal is expanded at the rear stage of the digital signal
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processing circuit. Therefore, the limitation of the dynamic range of the audio signal supplied
from the microphone to the digital signal processing circuit is alleviated, and it is possible to
improve that the audio signal input to the digital signal processing circuit is saturated and
distorted. Performance is improved.
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