To use a decibel meter, first ensure it has a battery, and then direct the microphone in it at the source you are testing to take the decibel measurement. To test specific frequencies between 500 and 10,000 Hertz, use "A-weighted." For the entire frequency range, use "C-weighted." For average sound levels, use a slow response time. For peak levels, use a fast response time.
When calibrating speakers, use pink noise found on a test CD. Use the meter to assess the sharp peaks or above average sound levels. Test the speakers at different parts of the room, and turn up the volume until the meter reads at zero. Play each test tone, write down the meter measurements, and find where the speaker produces measurements at zero for each tone. Adjust the speaker placement to achieve a zero reading.
When testing each speaker placement, secure the device to a tripod with the mount threads under the meter. This allows for an accurate measurement because you are near the meter, affecting the reading in any way. Raise the tripod to "ear" level, or an optimal listening position, and move away from the speaker. Be aware of any speakers that also utilize an equalizer to ensure it produces the best possible sound.