1) Auditory hallucination 2) Hallucination 
Rarely used term for an auditory hallucination in which indefinite sounds, such as ringing or hissing, are heard. ... Synonym: acouasm. ... Origin: G. Akousma, something heard ... (05 Mar 2000) ... 
acousma A simple auditory hallucination, such as ringing or buzzing sounds "in the ears"; also acouasm.