Auditory processor
The auditory processor was a Borg implant that controlled hearing, and also affected speech.

In 2376, The Doctor, with his ethical subroutines deleted by the  crew, performed an operation on Seven of Nine to extract her cortical array. During the procedure, he manipulated her auditory processor, so that she unconsciously accompanied him on a duet of "Oh My Darling, Clementine". ()

See also
Audio implant
Borg components