Pervasiveness of Early Middle Ear Muscle Contractions
Abstract
Middle ear muscle contractions (MEMCs) are expected to reduce the transmission of energy through the middle ear. Some damage-risk criteria (DRCs) for impulsive noise include MEMCs as a form of protection. Early MEMCs (eMEMCs) have been assumed in some DRCs to reach maximum effect prior to the arrival of the hazardous impulse. Despite decades of conjecture leading to the inclusion of eMEMCs in DRCs, there is no conclusive evidence of protective eMEMCs in the scientific literature. The inclusion in MIL-STD-1474E of one model utilizing eMEMCs elevates greatly the need for certainty that eMEMCs are pervasive (i.e., present in 95 percent of the population with 95 percent confidence) in the military population. The current study was designed to determine whether eMEMCs are pervasive in the military population, either as conditioned responses or the result of prior experiences. Participants were adults with excellent or very good hearing sensitivity, and no evidence of dysfunction affecting the ear or relevant cranial nerves. Changes in the levels of a click-based probe signal developed in the ear canal were used as the indicator of MEMCs. None of the experimental tasks tested here produced proportions of eMEMCs approaching the requirement for pervasiveness. There was a very low likelihood of observing an eMEMC for any of the tasks relying on prior experience.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 11, 2020
- Accession Number
- AD1119686
Entities
People
- Gregory A. Flamme
- Heath G. Jones
- Kristy K Deiters
- Madeline V. Smith
- Nathaniel T. Greene
- Stephen M. Tasko
- William A. Ahroon
- William J. Murphy
Organizations
- United States Army Aeromedical Research Lab