I should add that buzzing in the head can also be medication-related. It could be as innocent as med withdrawal effects. For example, some meds (often antidepressants) are known to cause "brain zaps" during withdrawal. See Brain zaps: Definition, causes, and how they feel

Or buzzing sounds perceived (see Tinnitus causes: Could my antidepressant be the culprit? - Mayo Clinic)

Again, in the links above the causes range from quite innocent to a bit less so.