PURPOSE: To prevent an emotion unstable phenomenon and to secure a comfortable living space by radiating an ultrasonic sound to the internal part of a closing construction.

CONSTITUTION: A microphone 3 is located outside a closing construction 1 and gathers an external acoustic sound. A filter 4 is a high-pass filter or band- pass filter to pass only the signal of an ultrasonic band and to interrupt the others among sound signals gathered by the microphone 3. An interrupting frequency is made into the degree of 10KHz, and in the case of the band-pass filter, it is made into the degree of 10W30KHz. The signal to pass the filter is amplified by an amplifier 5 and radiated in a room by a loudspeaker 6. An external surrounding noise is dummily generated. The output of a signal generator 7 can be radiated from the loudspeaker 6 by being amplified by the amplifier 5. The signal generator 7 generates a white noise by using, for example, a shift register. Through an electric equalizing circuit, a correction to a pink noise can be easily executed. A reproduction may be executed by gathering ultrasonic noises into a memory beforehand.