B&K 2250 Light, User Manual, Page: 186 / 208

2250 Light – User Manual 176
Our hearing covers a surprisingly wide range of sound pressures – a ratio of over a million to one. The
dB scale makes the numbers manageable
Dose, ProjDose: The Noise Dose is the equivalent averaged A-weighted Noise Level (taking
the Threshold Level into account) using Exchange Rate = 3 for an 8 hour
period (reference duration) relative to the maximum allowed (the Criterion
Level) – expressed in percentage.
Example: If the Criterion Level is 85 dB and a person is exposed to a constant
sound pressure level of 85 dB for 8 hours, then the Dose is 100%. A constant
level 88 dB results in a Dose of 200% and a constant level of 82 dB results
in a dose of 50%.
The Projected Dose is the Noise Dose based on measurement duration less
than 8 hours, assuming the sound level for the remaining time stays the same.