PURPOSE: To inspect a quality of a reproduced signal of a device under inspection without individual differences by reporting the state when the signal, from which a fundamental frequency component is removed, exceeds a threshold value with respect to the fundamental frequency component.

CONSTITUTION: A sine wave reference signal from a test CD is supplied to a half-wave rectifier circuit 8 and a band-removing filter 31 through an amplifier 6. When clicks are included in the sine-wave reference signal, the pointer of a distortion meter 12 shakes in response to the signal which has undergone half-wave rectification by a half-wave rectifier circuit 37. When the half-wave rectified signal from the circuit 37 exceeds the threshold value of a comparator 38, the output of the comparator 38 is at a 'H' level. At the time of the 'H' level, an alarm LED41 is lit, and the state is visually notified to an inspector. A multivibrator 39 is triggered at the 'H' level, and pulses are outputted for a specified period. Thus, a buzzer 40 is sounded.