Tinnitus is a neurological condition usually caused by any form of hearing loss from ear wax to sensori-neural, but it can also be brought on by neck jaw issues or head trauma
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4208401/
Hearing Loss
https://trainingandrehabilitation.com/association-tinnitus-neck-tmj/
https://www.dizziness-and-balance.com/disorders/hearing/tinnitus/cervical tinnitus.html
Neck/Jaw and TMD
https://www.virginiatrialfirm.com/blog/2013/may/traumatic-brain-injury-tinnitus-ringing-in-the-e/
Head trauma TBI
Does he have hearing loss or trouble hearing in background noise?
if he was exposed to loud noise a lot such as concerts, mp3 palyers, a band then yes.
Does he have TMD neck/jaw problems?
Did he suffer a head injury?
Does he have sensitivity or painful sensitivity to noise? (hyperacusis)
Does he have balance issues?
Does his tinnitus get louder when he yawns or turns his neck side to side?