PURPOSE: To obtain a switching device which has no mechanical contact pieces and no thrusting portions by providing a switching circuit which outputs switching signals when the one-end opening of a cylindrical member is blocked or when a detected object gains access to the one-end opening.

CONSTITUTION: A cylindrical member 2 has one end A open and the other end provided with a standing-wave generating means 1 such as a dynamic speaker, a ceramic speaker or etc., which is driven at preset frequencies to generate standing waves in the cylindrical member 2, and with detecting portions 1a-1d to detect that, when the one-end opening A is blocked by an object 3 such as a human finger or when a detected object 3 gains access to the one-end opening A, the standing waves in the cylindrical member 2 is in an anti-resonant or resonant state and the drive coil 1b is at high impedance or low impedance, so that when high impedance or low impedance is detected switching signals can be output. It is thus possible to easily obtain an audible switching device which has no mechanical contact pieces and no thrusting portions.