acoustic

Concise Oxford English Dictionary © 2008 Oxford University Press:
acoustic /əˈkuːstɪk/

▶adjective

• 1 relating to sound or hearing.

  ■ (of building materials) used for soundproofing or modifying sound.

  ■ (of a device or system) utilizing sound energy.

  ■ (of an explosive mine) set off by sound waves.

• 2 (of popular music or musical instruments) not having electrical amplification.

▶noun

• 1 the properties of a room or building that determine how sound is transmitted in it.

• 2 (acoustics) [treated as sing.] the branch of physics concerned with the properties of sound.

– derivatives
acoustical adjective,
acoustically adverb,
acoustician noun.

– origin C17: from Gk akoustikos, from akouein ‘hear’.