Projected Dose

Dose measurements usually require the noise exposure to be measured over a full 8 hour working day. This can be simplified by using projected dose.

This Dose allows the present accumulated dose over the elapsed logged time duration to be projected forward to give the predicted 8 hour dose. This can be shown by the equation:
Projected Dose Equation
Where time is the elapsed time duration, in hours

The following should be taken into consideration when reporting projected dose figures:

  • The Projected dose assumes that the current dose rate will remain constant. ie the sound level does not change over the measurement period compared to the total 8 hours period.
  • The projected dose will be more accurate if the measurement duration is as long as possible.
  • Dose, and therefore Projected dose, are measured with ‘A’ frequency weighting selected.
  • If, say, a 12 hour day is word the 8 hour projected dose should simply be multiplied by 1.5 (ie 12/8) to calculate what the dose would be after 12 hours.

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