@article{ref1,
title="Effect of earplugs on passenger speech reception in rotary-wing aircraft",
journal="Aerospace medicine",
year="1971",
author="Williams, C. E. and Forstall, J. R. and Parsons, W. C.",
volume="42",
number="7",
pages="750-752",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0001-9402",
doi="",
url="http://dx.doi.org/"
}