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Otoacoustic Hearing Assessment (NEEMO-OAE)
Principal Investigators
Research Area:
Species Studied
Scientific Name: Homo sapiens Species: Human

Otoacoustic emissions (OAE) are physiologic signals that arise from vibration of the outer hair cells (OHC) in the cochlea of the inner ear. Outer hair cells are highly metabolically active, and can be damaged by ototoxic medications, hypoxia, and high-energy noise exposure. Since otoacoustic emissions arise from the outer hair cells and it is the outer hair cells that are most affected by noise exposure and other insults, measuring outer hair cell function using otoacoustic emissions can be a sensitive way to assess inner ear damage.

Otoacoustic emissions can be evoked by introducing tones into the ear canal at two frequencies (f1, f2) that have a defined relation to each other (f1/f2=1.2). This type of evoked OAE is called a distortion-product otoacoustic emission (DPOAE). DPOAEs are frequency specific and usually can be detected in people with hearing thresholds of 50 dB or better. DPOAE testing can provide insight into potential hearing damage before pure tone audiometry thresholds change; it can potentially be used to identify noise-susceptible individuals. Reduction of DPOAE amplitude has been observed with short (hour) and long-term (years) noise exposure. Recent NASA-sponsored research has shown that DPOAEs can be reliably measured in a noisy environment using passive hearing protection, and they are repeatable over time.

Otoacoustic hearing assessments were evaluated as a screening tool to assess vulnerability to barometric pressure related hearing loss. Otoacoustic emissions are an objective, noise-tolerant technique and are therefore well suited for use in operational environments.

The objective of this project was to validate the procedures and verify the repeatability of self-administered tests in an operational setting. These data are important for successfully completing the planned otoacoustic emissions measurements on the International Space Station.

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Buckey JC Jr, Musiek FE, Kline-Schoder R, Clark JC, Hart S, Havelka J. Hearing loss in space. Aviat Space Environ Med. 2001 Dec;72(12):1121-4.[]

Audiometry, pure-tone
Auditory threshold
Hearing disorders
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Data Information
Data Availability
Archive is complete. Data sets are not publicly available but can be requested.
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Distortion product amplitude
Frequency intensity
Hearing acuity
Interactions, number
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Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
NEEMO 4 09/23/2002 09/27/2002 5 days
NEEMO 5 06/16/2003 06/29/2003 14 days

Additional Information
Managing NASA Center
Johnson Space Center (JSC)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Pamela A. Bieri
Institutional Support
National Aeronautics and Space Administration (NASA)
Alternate Experiment Name