Measurement of very high frequency (VHF) sound in our daily experiences

Abstract

Recently, it is frequently reported that very high frequency (VHF) sounds are emitted from daily necessaries such as home electric appliances. Although we measured VHF sounds from home electric appliances in our previous study, the origins of such VHF sounds have not yet been identified. In the present study, we tried to identify the VHF sound source in each home electric appliance using a "sound camera", which visualizes the spatial distribution of the sound intensity using a microphone array. The sound camera visualized the location of the sound source at frequencies from 2 to 52 kHz with a field of view of 63 degrees. The sound camera elucidated that the VHF sounds were emitted from the power source of a LET light, the ventilation duct of an electric fan, and the body of an IH cooker. Their frequency characteristics were dependent on the sound source, i.e., combinations of pure tones in the LED light and distributing in a wide frequency range in the electric fan.