I have the same. I'm afraid I have to report that my condition was thoroughly investigated when it first started, even under anaesthetic, with the ENT team.
No cause was found, other than tinnitus being there. You learn to live with it and, get used to it.
On top of this I have a heart beat that seems to skip a beat but is really just beating twice, and I don't hear the 2nd beat.
There is no relief but, "familiarity breeds contempt" and you get used to it.
Some people get this really bad and it disrupts their sleep. At AOHL they recommend listening to something quietly.
Tinnitus is when the ear is straining to hear something or anything when it is quiet, so listening to something else may help.
Might i make a point here as we may be misleading the OP in some of our answers.
The wife of the OP is suffering from PULSATILE TINNITUS which is quite different in cause and management from the more commoner inner ear nerve damage tinnitus.
Pulsatile tinnitus makes up about 3-5 % of all cases of tinnitus and is due to an abnormality of blood flow.Masking procedures e.g listening to music or tinnitus maskers, have no part to play in this type of tinnitus.