What does acoustics mean?
The definition of acoustics
A*cous”tics (#; 277), n.
Etym: [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.