Copyright © American Speech-Language-Hearing Association From: An Electroacoustic Analysis of Over-the-Counter Hearing Aids Am J Audiol. 2008;17(1):14-24. doi:10.1044/1059-0889(2008/003) Legend: The three audiometric configurations used in the study. Symbol key: ○ = Audiogram 1 (mild-to-moderate high-frequency loss); x = Audiogram 2 (moderate to moderately severe, sloping hearing loss); □ = Audiogram 3 (flat moderate hearing loss). Date of download: 11/15/2017 Copyright © American Speech-Language-Hearing Association