If your SPL Meter is a portable model, install the battery. Turn the meter on.
Adjust the sound range until a reading appears on the meter.
Set the response time. A low response time will result in a faster readout, while a high response time will result in a less accurate, but more steady readout.
Set the meter's weighting. This setting effects the meter's frequency response curve, allowing the user to fine tune the meter for various applications. Many meters roll off a low frequency response to measure sound pressure levels in an ambient setting, as opposed to a musical setting.
Read the level indicator. The number indicates in decibels the sound pressure level above the threshold of human hearing.