Sound Pressure Levels, or SPL’s, are a measurement of how efficient a given speaker is able to perform. There is a very complicated algorithm that is used to compute this, and the result is given in a unit called decibels, or Db. The testing process is fairly straightforward. A speaker is hung in a soundproofed room with a very accurately calibrated microphone. On the equipment end of the microphone is an extremely accurate meter that will measure both current and voltage from the microphone. A number of tones that fall within the frequency range of the speaker are fed to the speaker by a signal generator. One watt of power is produced by the signal generator and fed to the speaker. The voltage and current levels are recorded for each frequency reproduced. These readings are averaged and the algorithm is used to determine the SPL in Db’s.
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