| 摘要 |
PURPOSE:To easily prevent a howling from occurring by shifting, when amplifying an inputted sound and outputting through a loudspeaker, the entire spectrum of the inputted sound slightly toward the lower frequency waves or the higher frequency waves simultaneously with the a amplifying. CONSTITUTION:An original signal, for instance, of a sound signal (fa) of a certain level is inputted to a mixer 22 from an input terminal. Then a high frequency component (f0) whose frequency is sufficiently higher than the fa is generated by a transmitter 27, and the mixer 22 amplitude-modulates the f0 with the fa. The output of the mixer 22 is filtered by a BPF 23, and only the upper side band wave of the modulated signal is taken out. Thereafter an oscillator 28 oscillates a wave at f0+ or -DELTAf (DELTAf is a very small amount), which is mixed with the output from a BPF 23 by a mixer 24. Then an LPF 25 cuts off the f0, and fa+ or -f0 is outputted. f0 is in such small amount as not noticeable through auricles. In such way, the howling is effectively prevented from occur ring. |
