Abel, S.M., A. Sass-Kortsak, and A. Kielar. 2001. “The Effects of Safety Gear Worn in Combination and Hearing Loss on Earmuff Attenuation and Speech Understanding”. Canadian Acoustics 29 (3):50-51. https://jcaa.caa-aca.ca/index.php/jcaa/article/view/1379.