Can anyone ID this chirping noise?!

Have had this high-pitched chirping sound for the last few days. I went through a pretty exhaustive process of elimination:
– Changed chain
– Removed jockey wheels and their dust caps and put a drop of oil in both
– Tried two different thru-axles (both with a little grease applied)
– Tried with a different cassette
– Checked wheel hub by removing end caps, added small amount of grease
– Removed disc rotor

None of these things made much difference.

I then removed disc rotor, cassette and chain and spun the wheel freely and I still heard the noise although it seemed less pronounced.

When I replaced everything and turned the cranks with bike in the stand, the sound was still very audible.

I have tried to hold my ear as close as possible to hear where the sound is coming from but it’s impossible for me to identify but I can only think it’s coming from the hub. However, when I took the wheel out, removed rotor and cassette and spun it on a thru axle, I couldn’t hear the sound!

When riding the bike, the sound comes and goes. Yesterday it was very audible at the start of the ride then much less so after 20km.

Any suggestions welcome.

Can anyone ID this chirping noise?!
byu/CornwallJon inbikewrench

by CornwallJon