Emily Dickinson Lexicon

A-COUS'TICS, n.

1. The science of sounds, teaching their cause, nature, and phenomena. This science is, by some writers, divided into diacoustics, which explains the properties of sounds coining directly from the sonorous body to the ear; and catacoustics, which treats of reflected sounds. But the distinction is considered of little real utility.
2. In medicine, this term is sometimes used for remedies for deafness, or imperfect hearing. – Quincy.