| 摘要 |
PURPOSE:To let a user notice a surrounding noise level and enable him to make an appropriate voice level call by providing a level meter indicating peripheral noise levels to a loudspeaking telephone set. CONSTITUTION:Transmission rectification output of a transmission rectification circuit 11 drives a level meter 15 through a meter driving amplifier circuit 14. In normal condition of distinguishing a periphery noise from sound signals, an easy noise meter can be constituted, which indicates noise levels to be inputted in a microphone 1 on a level meter 15 by giving characteristics analogous to audible sense correction characteristics A of JIS C1502 to frequency characteristics of the circuit 11 because accoustic energy of the periphery noise is in most part contained in a low frequency area. Therefore, in case of a user not uttering any sound, the user can know proper sound level because the meter 15 displays the periphery noise level collected. |
