Sound reproducing device

Details Sound reproducing device Sound reproducing device

2000-05-25

2002-04-09

Harvey, Minsun Oh (Department: 2644)

Electrical audio signal processing systems and devices

Including frequency control

C381S097000, C381S059000, C381S056000

Reexamination Certificate

active

06370253

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an audio reproducing apparatus for reproducing a quality signal in a rather noisy environment.
BACKGROUND ART
FIG. 8
is a block diagram illustrating a conventional audio reproducing apparatus. In
FIG. 8
, an input signal received by input terminal
1
is fed into power amplifier
3
via gain-control-circuit
2
. An output signal supplied from power amplifier
3
is fed into speaker
4
mounted to baffle
5
and then reproduced. Microphone
6
disposed around speaker
4
collects signals radiated from speaker
4
together with the noises around baffle
5
. An output signal supplied from microphone
6
and the output signal from amplifier
3
are fed into subtractor
7
, where the input signal component is deducted from the sum of the radiated signal from speaker
4
and the noise around, thereby extracting the noise component around baffle
5
. An output signal supplied from subtractor
7
is proportionate to the noise around and restricts a bandwidth of the noise around via low-pass-filter
8
. An output supplied from low-pass-filter
8
is converted from ac to dc by rectifying circuit
9
and then supplied to gain-control-circuit
2
disposed at a stage before amplifier
3
. This structure allows gain-control-circuit
2
to change automatically an amplitude of an input signal responsive to the noise around speaker
4
so that the signal radiated from speaker
4
can be prevented from being masked by the noise around.
However, a conventional audio reproducing apparatus produces a difference between a signal component radiated from speaker
4
and that supplied from amplifier
3
, thus subtractor
7
cannot completely remove the signal component radiated from speaker
4
. Therefore, the noise component around the speaker is hard to be extracted, whereby the noises within only a limited bandwidth can be restricted.
SUMMARY OF THE INVENTION
The present invention aims to provide an audio reproducing apparatus that removes a signal radiated from a speaker correctly, and changes a gain responsive to noises around.
In order to achieve this objective, the audio reproducing apparatus of the present invention prepares a microphone disposed around a speaker and a detecting means for detecting a movement of a voice coil of the speaker. The microphone and the detecting means extract a noise component around. This structure allows the noise component around the speaker to be extracted correctly, so that masking compensation can be performed in a natural manner.


REFERENCES:
patent: 6122385 (2000-09-01), Konno et al.
patent: 1-282996 (1989-11-01), None
patent: 5-30588 (1993-02-01), None
Japanese search report for PCT/JP99/03502 dated Aug. 24, 1999.
English translation of Form PCT/ISA/210.

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