A bit of history on standards for acoustical measurements of hearing aids.
Lybarger
S F
SF
Radioear Corporation, McMurray, PA, USA.
Preves
D A
DA
Olsen
W O
WO
D001298:Audiology / Q000266:history; D006310:Hearing Aids / Q000266:history* / Q000592:standards*; D049673:History, 20th Century; D013061:Speech Acoustics; D014481:United States