Why do we calibrate sound level meters to 94dB?
94 dB is equivalent to a sound pressure level of approximately 1.0 Pa – a nice, round, convenient number that also works as a reasonable point of reference. SPL = 20 log( P / Pref ) Where Pref = 2.0E-5 Pa A 94 dB reference point is moderately loud, but not so loud as to produce distortion in the measurement instrumentation or so quiet as to cause the measured signal to be contaminated with background noise (i.e., the instrument’s noise floor). Remember that standards such as these were developed when instrumentation was far less sophisticated than it is today and is used with all grades of instrumentation (Type 0, laboratory; type 1, precision; type 2, general-purpose; type 3, survey).
