\A*cous"tics\ (#; 277), n. [Names of sciences in -ics,
as, acoustics, mathematics, etc., are usually treated as
singular. See {-ics}.] (Physics.)
The science of sounds, teaching their nature, phenomena, and
laws.
      Acoustics, then, or the science of sound, is a very
      considerable branch of physics.          --Sir J.
                                               Herschel.
Note: The science is, by some writers, divided, into
      diacoustics, which explains the properties of sounds
      coming directly from the ear; and catacoustica, which
      treats of reflected sounds or echoes.