Relation of physical characteristics of foam earplugs to insertion loss

The relation between the physical characteristics of foam earplugs (i.e., weight, length, width, density, expansion pressure, and expansion force) and attenuation in high noise levels (105 dB SPL) was investigated using KEMAR. The results indicated that all commercial polymer foam earplugs have similar physical properties; frequency (Hz) is the single most important variable in determining attenuation of foam earplugs; and chlorination seems to have a pronounced effect on attenuation. The measured attenuation does not change in a consistent manner with changes in physical properties which may reflect an incomplete understanding of cause-effect relationships between the variables studied.