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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
echo canceller for removing echo (reverberation) in a hole or the like. [Background of the
invention] There are some halls and the like that are designed in consideration of reverberation
characteristics, but when music or the like is emitted by a speaker in a hall where the
consideration has not been taken into consideration, the original sound is echoed. It is very
annoying to the audience. SUMMARY OF THE INVENTION An object of the present invention is
to provide an echo canceller which can effectively cancel such an echo. [Means for Solving the
Problems] For this purpose, the present invention is a series connection of a delay circuit for
delaying the phase of an input signal, a gain setting circuit for adjusting the gain, and an
equalizer for setting the passband frequency. The output of the circuit is added to the above
input signal, and the added output is input to the speaker. The present invention will now be
described by way of examples. As shown in FIG. 2, when the speaker 2.3 is placed on the front
side of the hole 1 and emitted from there, the sound waves A and B are reflected by the opposite
wall 1a and echoes A 'and B are generated. 'Become spectator seat (reference position) 4 and
return. The echoes A 'and B' arrive after a lapse of time after the sound waves A and B have
arrived, as shown in FIG. Therefore, if a sound wave having the same level as that of the echoes A
'and B' in phase opposite to that of the echoes A 'and B' is emitted from the speaker 2.3, the
echoes A 'and B' are canceled. FIG. 1 is a block diagram of an echo canceller therefor. An audio
signal to be reproduced by the speaker 2 is input to the input terminal 10, and an audio signal to
be reproduced by the speaker 3 is input to the input terminal 11. Then, the audio signal input to
the input terminal 10.11 is converted from an analog signal to a digital signal of about 8 bits by
the A / D converter 12.13, then manually input to the addition point 14.15, and output therefrom
Then, it is converted back to an analog signal by the D / A converter 16.17, and input from the
output terminal 18.19 to the speaker 2.3. Between the A / D converter 12.13 and the summing
point 14.15, only the delay circuit 20.21 using a memory, the gain (attenuation) setting circuit
22.23, and a signal of a specific frequency band are used. Equalizers 24.25 to be passed are
connected in series. Here, the delay time of the delay circuit 20.21 is adjusted to the time
obtained by adding the time for inverting the signal to the time t in FIG. 2 and the attenuation
amount of the gain setting circuit 22.23 is output at the spectator seat 4 The sound wave is
adjusted to be at the level of the echo A'B ', and the equalizer 24.25 works as a low pass filter of,
for example, a 4 kHz cutoff frequency.
Thus, when an audio signal to emit sound waves A and B is input to the input terminal 10.11, the
sound wave ASB is immediately emitted from the speaker 2.3. Then, after that, the sound wave
for cancellation of the 4 KHz or less component of the signal whose level is set by delaying the
sound signal is emitted from the speaker 2.3. This component is an inverted sound wave of the
same level as that of the echoes A 'and B', and the echo A'B 'in the spectator seat 4 is canceled by
the canceling sound wave from the speaker. The central audience seat 4 is preferably the center,
but can be adjusted by setting the delay amount by the delay circuit 20.21 and the attenuation
amount by the gain setting circuit 22.23. From the above, according to the present invention,
there is an advantage that echo removal in holes can be performed effectively and easily.
Brief description of the drawings
FIG. 1 is a block diagram of an echo canceller according to an embodiment of the present
invention, FIG. 2 is an explanatory view of an echo generation, and FIG. 3 is an explanatory view
of an echo.
DESCRIPTION OF SYMBOLS 1 ... Hall, 2.3 ... speaker, 4 ... spectator seat (reference position)
10.11 ... input terminal 12.13 ... A / D converter, 14.15. · · · Addition point, 16.17 · · · D / A
converter, 18. 19. · · · output terminal, 20.21 · · · delay circuit, 22.23 · · · gain setting circuit, 24.25
· · · ·equalizer. Figure 1 Figure 2
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