JPS6482890A - Sound output device - Google Patents

Abstract

PURPOSE:To improve the howling preventing effect, and to enlarge the degree of freedom at the time of using by constituting the titled device of an input part, a converting part for working a sound signal, an amplifying part for executing a variable gain amplification in accordance with a waveform and a frequency of the signal, and an output part. CONSTITUTION:This device is constituted of an input part 1 consisting of a microphone and a band limiter, a converting part 2, an amplifying part consisting of a pre-amplifier and a variable gain amplifier 5, and an output part 4 consisting of a cone loudspeaker. The converting part 2 is constituted of an integrator consisting of an integration circuit and a correcting circuit for correcting its value to match an electric circuit of the post-stage, a square device for squaring a sound signal and an output of the integrator respectively, an adder for adding the respective outputs, a high-pass filter for bringing said output to filtering and detecting an AC component, and a gain limiter for receiving its output, and the gain limiter can increase an amplification factor of the variable gain amplifier by about 80dB in case when the AC component exists, comparing with the case when it does not exist. That is, the variable gain amplifier repeats alternately the amplification factor between 80dB and 0dB in accordance with whether the AC component exists or not.