| 摘要 |
PURPOSE:To automatically adjust the sound volume in response to the noise level in the environment by converting the noise inputted from a microphone from AC to DC signal and changing the audio signal generated in the audio system in proportion to the noise signal level subjected to DC conversion. CONSTITUTION:The microphone 1 inputs the external noise at reproduction and a voice to be recorded at recording, and a switch section 2 switches the inputted voice by the microphone 1 to an AC-DC conversion section 4 at reproduction and the reproducing/recording section 3 at recording. Moreover, the voice inputted from the microphone 1 at reproduction is recorded by a reproducing/recording section 3 and the noise inputted from the microphone 1 is converted into a DC level signal proportional to the noise level by the AC/DC conversion section 4. Thus, even if a surrounding noise level is changed, the sound is listened always to a proper level automatically.
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