Auditory processor

From Memory Alpha, the free Star Trek reference

The auditory processor is a Borg implant that controls speech.

In 2376, the Doctor, with his ethical subroutines deleted by the USS Equinox 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 "My Darling Clementine". (VOY: "Equinox, Part II")