VALIDATION OF THE CSA Z107.56 STANDARD METHOD FOR THE MEASUREMENT OF NOISE EXPOSURE FROM HEADSETS
The CSA Standard CAN/CSA-Z107.56-06 (R2011) “Procedures for the Measurement of Occupational Noise Exposure” deals with noise exposures found in industrial settings, where in most situations, the noise source is in the far field. The Standard also provides procedures for the measurement in situations where the noise sources include sources in the near field, which is the case with headsets. The procedures involve the use of sophisticated equipment and techniques that are generally difficult to implement in the workplace. However, the Standard also provides a simple calculation method that only requires the measurement of the background noise level using a sound level meter or a dosimeter. The calculation method assumes a signal-to-noise ratio (S/N) of 15 dBA, to ensure the most comfortable listening level for speech understanding. The noise exposure level of the ear under the headset is thus obtained as the sum of the background noise level (corrected for headset attenuation and duration of the signal) plus 15 dBA for the S/N. The objective of the present study was to assess the validity of the calculation method under different background noise conditions. Three different background noises were played at three sound levels. The noise exposure level under two headsets with different attenuations was assessed using a speech in noise paradigm. Participants were asked to adjust the signal level to comfortably understand the speech. The increase in sound level was measured for each combination of parameters using an artificial ear.
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