9320 Reference Controller Operating Manual 38 (52)
Several weighting options are available for the SPL display. The weighting option is selected in the GLM
configuration.
The audio signal for the sound level and noise dose measurements can come from the measurement
micorphone in case of loudspeaker-based monitoring or from the audio input directly in case of
headphone monitoring.
Fig. 32. Principles of obtaining the audio signal for SPL mearument and noise dose integration.
8.8.1 Principles of Exposure Calculation
The noise dose calculation (Table 1) works with the assumption that a constant noise level under the
noise dose safety limit for the duration of accumulation set in the national standard is unlikely to result in
a permanent hearing damage over time. The calculation of accumulation assumes that the listener is
exposed to the noise for the duration of a standard working day. Then, the noise dose accumulates to
100% during the standard working day, and this describes the limit of safe working conditions.
In media work, audio signal level variation is dynamic, and this must be considered. This is done by
using the exchange rate. The exchange rate explains how much dose accumulates at various listening
levels. This means that if the noise level is higher by the amount given as the threshold level, the
duration of accumulation is speeded up. The accumulation rate is doubled if the exceeds the threshold
by the amount shown in the exhange rate. If the threshold is at 80 dB SPL, but the actual sound level is
86 dB SPL, the daily dose accumulates in ¼ of the standard working day when the exchange rate is 3
dB and the sound level exceed the threshold by 2 x 3 dB = 6 dB. When the noise level is below the noise
dose threshold limit, this low level is considered safe and does not contribute to the noise dose for the
day.
Fig. 33. Selecting the noise dose standard, SPL reading weighting and reset of accumulated dose.
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