Date of Graduation


Document Type


Degree Type



Statler College of Engineering and Mineral Resources


Industrial and Managements Systems Engineering

Committee Chair

Steven E. Guffey

Committee Co-Chair

Ashish D. Nimbarte

Committee Member

Mohammad A. Virji


Earmuffs provide necessary protection from the hazardous effects of noise for workers and the general population. The wearability and effectiveness of these devices is crucial for protection of hearing in noisy conditions. One component critical to the function of the earmuff is the clamp force that keeps the earmuff securely against the head and around the pinna. This clamp force must be high enough to provide a good seal, but not so high that it makes the muff uncomfortable. This study investigated the relationship between noise reduction (NR) and the force on the ear. This force was incrementally varied by attaching counter weights, ranging from 200--1200 grams, to the muffs. The NR values for four (4) muffs used by six (6) human subjects were determined in a reverberation chamber using the MIRE test method. Each muff-subject combination was tested twice. When all muffs were considered as a group, at least one NR test value was below 10 dBA for test forces in the range of 0.9--2.3 lbs. However, if the Bilsom was not considered, there were no NR 15 dBA was 1.95 lbs. It is doubtful that increasing the total force would improve performance further. As expected NR values fell with decreasing force on the ear (p < 0.01). Subject, MuffId and the interaction of MuffId and Subject all showed significance (p < 0.001).