Check the fan belt. It is a known location for “belt squeal” or slight belt slip. My car had that and I cured it by taking the belt off and cleaning the pulleys and wiping the belt clean. I think ( it was several years ago) I used brake cleaner on a cloth for the pulleys to avoid overspray onto bearings etc and meths on a cloth for the belt. Refitted the belt and tensioned it. No noises after that. The noises pre cleaning came and went as revs changed and MIGHT be the case with your car. A simple job that can find or eliminate the cause.
Gomog has a section on it and another option was to replace the belt with a slightly narrower one.
