Background
Home appliances, such as the refrigerator, TVs, air conditioners, andmobile devices, have become an indispensable part of people’s lives. According to statistics[1], the overall appliances market is predicted to be more than 450 billion dollars by 2023. Recognizing the working appliances is of great importance for smart environment to provide services including energy conservation, user activity recognition, fire hazard prevention, etc.
[1]Statista. Household appliance retail sales value worldwide in 2014, 2018 and2023, by category. http://www.statista.com/statis
SMPS uses a switching element to transform the incoming power supply into a pulsed voltage and then smooths. SMPS repeats the ON-and-OFF operation at high frequency of 100kHz∼6MHz. When the SMPS is working, the transformer, inductance and capacitors in SMPS can both generate high frequency sound. The high frequency switching of SMPS results in high frequency alternating current and strong alternating magnetic field. The magnetic core and coil inside a transformer is seriously affected by the magnetic field. Under the influence of magnetic force, if periodic vibration, friction, material deformation, etc. happen to those magnetic materials, then high-frequency sound is produced. The similar phenomena is with the capacitor and the inductor.