Fig. 2

Measurement of the acoustical properties of the powered air-purifying respirator (PAPR) system. A Illustration of the PAPR system on a head and torso simulator used for measurements. B One-third octave band noise levels (dB SPL) of the PAPR system (black line) and the noise floor of the anechoic chamber (grey line). C Frequency spectrum of the sound insulation (dBr) of the PAPR calculated as difference between the transfer functions to the position of the left eardrum with and without PAPR system