Hi Roy,
Welcome to the forum!
If I put my ear against the body of my R5 when it's on I hear a
very faint 'tech-whir' sound. If this is what you're hearing I believe it's normal - so don't worry.
(I hear exactly same noise with my wife's R7).
Otherwise, although you say it isn't focus hunting, my first thought regarding 'unusual noise' would be 'Continuous AF'. I believe this feature is enabled by default - but it's a real battery drain so I always disable it. If it's enabled try disabling it to see if that makes a difference.
Phil
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