Field evaluation of ear-muffs: Which is more suitable—insertion loss or transmission loss?

Abstract Among the complementary procedures for the subjective measurement of the attenuation characteristics of ear-muffs through the real ear attenuation at threshold, the most widely used are several objective paradigms. Measurements can be performed through Insertion or Transmission Loss procedures; nevertheless, they give different attenuation values in the mid- and high-frequency range, not explained in the literature. This paper describes the origin of these differences, that are attributable to diffraction effects, demonstrating the equivalence of both magnitudes through a measurable parameter.