WRIGHT-PATTERSON AIR FORCE BASE, Ohio (Dec. 7, 2018) In support of Naval Medical Research Unit Dayton's Environmental Health Effects Laboratory (NAMRU-Dayton/EHEL) hearing health research, Dr. Rachel Howes, audiologist, uses an array of auditory testing devices to measure distortion product otoacoustic emissions and broadband (click) and narrow frequency (tone burst) auditory brainstem response. (U.S. Navy photo by Megan Mudersbach)