Source : Webster's Revised Unabridged Dictionary (1913)

Phonetics \Pho*net"ics\, n.
   1. The doctrine or science of sounds; especially those of the
      human voice; phonology.

   2. The art of representing vocal sounds by signs and written
      characters.

Source : WordNet®

phonetics
     n : the branch of acoustics concerned with speech processes
         including its production and perception and acoustic
         analysis