The calibration certificate of the sound level meter is useless. Only if a calibration certificate is issued and a qualified conclusion and accuracy level are obtained, it can be used normally. The daily calibration of sound level meters requires a lot of equipment, including calibrators, standard condenser microphones, signal generators, measurement amplifiers, burst signal generators, precision attenuators, voltmeters, sound sources, mufflers (free field), etc. It requires at least 30W to be fully equipped, and it occupies a large space and has certain technical requirements; at the same time, there are not many instruments for sound level meter verification, and the standard equipment must be submitted for inspection every year, so establishing a complete set of acoustic verification equipment is not cost-effective, resulting in Many provincial metrology institutes have not established sound level meter calibration equipment and cannot issue sound level meter calibration certificates.