Ultrasonic detectors provide a method of detecting sounds greater than 20 kHz. Loose electrical connections emit characteristics sounds that are beyond the range of the human ear. The ultrasonic detector provides a method of converting inaudible sounds to sounds and tones that match our hearing capabilities. Flashovers across an insulator make crackling sounds that are detectable even when there are no visible signs of arcing. The basic operation of the ultrasonic detector is relatively simple. A transducer, generally equipped with some type of mechanical sound focusing aid, collects the sound energy and passes it to the amplifier, which feeds the modular section where the collected sound is mixed with a signal from the oscillator section. A typical use for the ultrasonic detector is detection of loose or arcing connections inside an enclosed cabinet or panel board.