Methods of objectively measuring the insertion loss of HPDs, including simulation of the bone conduction pathways

Abstract

While acoustical test fixtures (ATFs) for production testing of circumaural hearing protection devices (HPDs) have been shown to be practical (see related ISO‐ and ASA‐activities, for example), no ATF for intraaural HPDs has been standardized so far, and we are still far away from using artificial heads in type testing of HPDs. Additionally, an ideal ATF suitable for type testing of HPDs should also be eligible for measuring headphones of all kinds. This paper reviews the progress achieved in constructing ATFs by various researchers. Special emphasis is placed on the authors' own work, parts of which were presented at the 103rd and 106th meeting of the ASA: We attacked the elaborate goal of constructing an artificial head with appropriate circumaural and intra‐aural flesh simulations, which included a suitable ear simulator and a cast of an average pinna. Recently we have refined the method of taking bone conduction into account by including the vibration characteristics of circumaural HPDs and by modelin...