Microgravity presents a potential risk to astronauts’ hearing due to its noisy environment. Suitable countermeasures and effective protective devices need to be developed to deal with this risk. This study will provide an understanding of hearing physiology and clarify the effects microgravity has on hearing. Testing will be accomplished preflight, inflight, and postflight using various tests including Otoacoustic emissions (OAEs) testing and psychoacoustic tests, such as ABR, tone audiometry, and impedance tests. Customized hardware will also be used to quickly conduct high frequency-resolution OAE measurements utilizing three different techniques: transient-evoked, distortion product, and stimulus-frequency OAEs.
The goal of this testing is to identify any changes in the functionality of the astronauts’ hearing in microgravity for application to ISS or any long duration missions. This data can also be applied to clinical and occupational health settings.
The potential risk for transitory or permanent effects of microgravity and noise during long term missions has to be assessed in order to evaluate the need for suitable countermeasures and protective devices. These experiments will also have an impact on the basic understanding of the physiology of hearing, clarifying the effect of microgravity on the fluids of the delicate cochlear mechanisms. The development of a sensitive and portable OAE measurement device will find important applications in the clinical and occupational health practice.
Pre and postflight data collection will be performed utilizing a wide range of standard clinical tests of hearing and an extensive selection of advanced optoacoustic tests conducted on the Acoustic Diagnostics apparatus. Prfe-light testing will be conducted at launch minus sixty plus or minus ten days (L-60 + 10d). Postflight testing will be conducted at return from flight plus or minus five (R+5d) days. Three prime sessions and three reserve sessions will be conducted during the flight. The standard testing will involve standard tonal audiometry, impedance tests, Auditory Brainstem Response (ABR), psychoacoustic tests measuring the frequency, and time resolution (measurements of the tuning curve) of hearing.
The extended otoacoustic measurements with the Acoustic Diagnostics system will include Stimulus-Frequency (SFOAE), Distortion Product (DPOAE) , Transient-Evoked otoacoustic Emission (TEOAE) tests.
Inflight testing will be conducted over a short duration due to the limited time available for testing. Testing will be limited to a short automatic sequence of optoacoustic tests, requiring less than ten minutes for each ear as well as the high frequency-resolution DPOAE tests. Calibration and equalization of the stimulus in the ear canal will be performed before each measurement session. Customized software will be used to reduce the time needed for the crew to complete the testing inflight.
This is an international experiment. NASA does not currently have an agreement with international space partners to archive their data in the LSDA.