The CA51 accepted internationally 1 kHz
represents the "0 dB" reference point of A, B, C
Weighting and other filters utilized in acoustic
measurement. The Pistonphone - a mechanical
sound source - offers a slightly higher degree
of accuracy at a substantial increase in cost.
In addition, the 200 or 250 Hz operating
frequency is mechanically limited and not suited
for measurements of filtered inputs. The 0.2 dB
accuracy is quickly lost in the 0.7 to 1.5 dB
tolerances acceptable for weighting filters at
frequencies around 250 Hz. It's 94 dBSPL
due totheInternational standards
have established 1 Pascal (Pa) as 94 dBSPL. This
reference point is now accepted for specifying
the sensitivity of microphones. The uBar found
in some specifications refers to 74 dBSPL (20 dB
less than 1 Pa).
