Source : Webster's Revised Unabridged Dictionary (1913)

Audiometer \Au`di*om"e*ter\, n. [L. audire to hear + -meter.]
   (Acous.)
   An instrument by which the power of hearing can be gauged and
   recorded on a scale.

Source : WordNet®

audiometer
     n : an instrument used to measure the sensitivity of hearing
         [syn: {sonometer}]