In-Depth Survey Report: Comparison of Three Noise Reduction Rating Calculators for Passive and Active Hearing Protection Devices.

摘要

Active Noise Cancellation (ANC) hearing protection devices (HPDs) are evaluated for their passive attenuation and the active contribution to the total attenuation when the device is worn. The USAF Air Force Research Laboratory (AFRL) at Wright Patterson Air Force Base (WPAFB) conducted measurements of the real-ear attenuation at threshold (REAT) and microphone in real ear (MIRE) performance of four ANC earmuffs: Bose A20 Aviation headset, Pilot Independence DNC PA1779T headset, Sennheiser HMEC headset and the Telex Stratus Heli-XT Aviation headset. The octave band REAT attenuations were measured according to the ANSI/ASA S12.6-2008 standard. The one-third octave band MIRE data were measured and combined according to the ANSI/ASA S12.42-2010 standard to estimate the active component by measuring the device when it is turned on versus off. The total attenuation ratings from three calculators were compared for the overall Noise Level Reduction Statistic for A-weighting [NRS(A)] and the four values resulting from the Graphical Noise Level Reduction Statistics computed according to the ANSI/ASA S12.68-2007 standard. The three calculators were MATLAB(R) code, the ANSI/ASA S12.68 Excel spreadsheet and the HPDCalc software developed by NIOSH for the EPA. The rounded NRSA rating values for the 10th and 90th protection percentiles agreed. The NRSG values were determined to the hundredth of a decibel and the three calculators agreed to within 0.1 decibels.