| 摘要 |
PURPOSE:To automatically obtain a sound volume corresponding to the noise state of an environment and to prevent the excessive amount of volume from occurring by converting the sounds from the environment into an electrical signal, making the said signal to be an amplification-variable signal, and supplying it to an amplification circuit. CONSTITUTION:When an input is supplied from a microphone 2 or a magnetic tape reproducer 3 to the amplification circuit 1, the input signal is amplified by the circuit 1 and propagated from a speaker 4. A sound collector 5 detects the state of noise at all time and inputs a signal to an amplification circuit 6. A comparator 7 compares the output of the circuit 6 and the set value of a value-setter 8. In case the noise level from the environment is lower than the set value set by the setter 8, a command circuit 9 lowers the amplification ratio of the circuit 1. If the noise level is higher than the set value, the circuit 9 rises the ratio. The said comparison and judgment are executed at all time, however, at the time when the collector 5 receives a sound from the speaker 4 and the level rises instantaneously from the immediately preceding level, a control circuit 10 stops the operation of the circuit 9, and lets the circuit 9 amplify at the immediately preceding level. |
