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JPH05130691

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DESCRIPTION JPH05130691
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
earphone device, which is preferably applied to, for example, a headphone.
[0002]
2. Description of the Related Art Conventionally, when trying to listen to music in, for example,
the interior of a noisy train using a headphone stereo, external noise itself tends to be mixed in
through the headphone and raise the volume more than usual. On the contrary, the high-pitched
sound component leaking from the headphone may cause discomfort to the surrounding people.
[0003]
For this reason, only when there are many other people around, especially in a train car, etc., the
high pass component of the output audio signal to the headphone is reduced by a low pass filter
etc., thereby effectively enabling the high tone component leaking from the headphone. There
are headphone stereos designed to suppress.
[0004]
SUMMARY OF THE INVENTION In addition to the inevitable deterioration of the high-pitched
sound characteristics of the audio signal output from the headphone as a result, in the headphone stereo configured as above, it is possible to suppress the high-pitched component. There
was a possibility that the external noise would bother me and further increase the volume, which
was still insufficient for practical use.
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[0005]
Alternatively, it is possible to detect external noise with a microphone or the like, invert the
phase of the noise component obtained as a result, and feed back to the audio signal for output,
but this leads to cost increase. The design made it difficult to miniaturize the headphone stereo,
and it was still insufficient as a solution.
[0006]
The present invention has been made in consideration of the above points, and an object of the
present invention is to propose an earphone device capable of effectively suppressing noise
mixed from the outside with a simple configuration.
[0007]
SUMMARY OF THE INVENTION In order to solve the problems, in the present invention, a first
audio is obtained by inserting a series resistor R1 between the output stage 6 and the earphone 7
and obtaining the output stage 6 side of the series resistor R1. The noise component ΔN mixed
from the earphone 7 is detected based on the signal and the second audio signal obtained on the
earphone 7 side of the series resistor R1, and a delay noise component obtained by delaying the
noise component ΔN by a predetermined amount is output stage 6 To reduce the noise
component ΔN. .
[0008]
The noise component ΔN mixed from the earphone 7 is detected based on the audio signal
obtained on the output stage 6 side of the series resistor R1 inserted between the output stage 6
and the earphone 7 and the earphone 7 side, and the noise component thereof By feeding ΔN
back to the output stage 6, the noise component ΔN can be reliably reduced with a simple
configuration.
[0009]
An embodiment of the present invention will be described in detail with reference to the
drawings.
[0010]
In FIG. 1, reference numeral 1 generally indicates a headphone stereo according to the present
invention, and an audio signal S1 recorded on a magnetic tape 2 is reproduced through a
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2
magnetic head 3 and equalized in an equalizer 4 according to the magnetic recording and
reproducing characteristics. 5 has been entered.
[0011]
The signal processing circuit 5 executes noise reduction processing as necessary for the input
audio signal S1, and performs level control and equalization control according to the user-set
volume and equalizer characteristics, and the resulting audio is obtained. The signal S2 is sent to
the output amplifier circuit 6.
[0012]
The output amplifier circuit 6 has an operational amplifier configuration with a low output
impedance, and the audio signal S2 is input to this non-inverted input terminal, amplified at a
predetermined amplification factor, and passed through a resistor R1 of about 6 to 10 Ω as an
output audio signal S2. It is sent to the headphone 7.
[0013]
Here, in practice, the voltage on the output amplifier circuit 6 side of the resistor R1 inserted
between the output amplifier circuit 6 and the headphone 7 in this way is only the component S
of the output audio signal S2 because the output impedance of the output amplifier circuit 6 is
low. Assuming that the external noise mixed in from the headphone 7 is ΔN and the impedance
of the headphone 7 is Z, the voltage of the resistance R1 on the headphone 7 side is expressed by
the following equation
[0014]
Therefore, in the case of this embodiment, these signals are respectively input to the inverting
input end and the non-inverting input end of the mixing amplifier circuit 8 of the operational
amplifier configuration, and the component S of the output audio signal S2 can be removed.
When gain adjustment is performed, a signal obtained by inverting the phase of the noise
component ΔN is output from the output terminal of the mixing and amplification circuit 8 as
expressed by the following equation.
[0015]
Therefore, this signal is delayed by a predetermined amount by the delay circuit 9 composed of
the resistor R2 and the capacitor C1 and controlled to a predetermined level through the resistor
R3 and input to the inverting input terminal of the output amplifier circuit 6, The external noise
ΔN can be reduced.
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[0016]
According to the above configuration, the noise component ΔN mixed in from the headphone 7
is detected based on the audio signal obtained on the output amplifier circuit 6 side and the
headphone 7 side of the resistor R1 interposed between the output amplifier circuit 6 and the
headphone 7 Since the noise component ΔN is fed back to the output amplification circuit 6, it is
possible to realize the headphone stereo 1 capable of reliably reducing the noise component ΔN
with a simple configuration.
[0017]
In the above embodiment, although the present invention is applied to the headphone system,
the present invention is not limited to this. For example, the present invention is not limited to
the small compact disk player or headphone for listening to a compact disk with a headphone. It
can be widely applied to electronic devices adapted to listen to audio signals.
[0018]
As described above, according to the present invention, the noise component mixed in from the
earphone is detected based on the audio signal obtained on the output stage side of the series
resistor interposed between the output stage and the earphone and the earphone side. Since the
noise component is fed back to the output stage, it is possible to realize an earphone device
capable of reliably reducing the noise component with a simple configuration.
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