Acoustic characteristics of respirators

In some workplaces, employees are obliged to wear a respirator to protect them from harmful substances. However, an acoustical problem with respirator design is that respirators diminish the voice. Frequency analysis of sound through respirators could help tackle the problems associated with this design. We used a mannequin with a loudspeaker attached to its mouth and emitting pink noise. We measured the noise with 59 combinations of respirators and filters. For half-face masks with one or two filters, attenuation of the noise under 1 kHz was relatively small. The attenuations over 1 kHz varied widely among the tested respirators. With full-face masks, the attenuated frequency was lower than with the half-face masks. Respirators with a speaking diaphragm conducted louder sound over 3 kHz than did respirators without a speaking diaphragm. Among disposable masks, the attenuations were smaller than with half-face masks. We discuss the requirements for smooth communication among workers using respirators in light of the attenuation values of respirators at different frequencies.