Effect of measurement method on an earmuff’s frequency response

Light, medium and heavy earmuffs’ amplitude frequency response was measured using
transmission loss technique with a microphone placed in subject’s ear (MIRE – microphone
in real ear) and on an artificial test fixture (ATF). Measurements were conducted in frequency
range up to 9 kHz employing maximum length sequence (MLS). This method shows details
of earmuffs’ amplitude frequency response, in contrast to sound attenuation data obtained
in octave bands according to the EN-ISO 4869-1 standard. The study compared ATF data
with results measured on a person when soft tissues influenced the ripples of the obtained
frequency response. Results were also judged against the sound attenuation data of the real
ear at threshold (REAT) method used in certification of hearing protectors.