Those who have done the development work have such experience, test switching power supply of LED Linear Light or in the experiment have heard similar products to play bad pressure leakage or high voltage pull the sound of uninvited: its sound is large or small, or Sometimes without; its rhythm or deep or harsh, or change all who have.
Audio noise generally refers to the switching power supply itself in the process of work, can be heard by the ears of the frequency of 20-20kHz audio signal. Electronic and magnetic components of the oscillation frequency in the human hearing range, will produce a signal can be heard. This phenomenon has been known at the beginning of power conversion research. Transformers operating at 50 and 60 Hz often produce annoying AC noise. If the load is modulated by an audio element, the switching power converter operating at a constant ultrasonic frequency also generates audio noise.
At low power levels, the audio signal is usually independent of the converter. However, the designer may wish to reduce the acoustic emission of its circuit. In a low-power AC-DC converter, the core sheets of 50 or 60Hz transformers are welded together to reduce the AC noise to an acceptable level. High-frequency switching converters in the ferrite transformer also uses a similar technology.
In the past, advanced audio engineering equipment was used to study the acoustic radiation of switching power supply. This device can measure the absolute sound pressure level and sound spectrum very accurately, but the human perception of the sound is very subjective. It is hard to say how much sound is heard and it is more difficult to determine how much of the sound in a particular application will be considered unbearable noise.
Sonic radiation is similar to electromagnetic radiation, but there is no general benchmark for measuring auditory tolerance. Therefore, the designer can handle the problems related to audio noise and reduce the sound radiation of the product according to the following guidelines.