2001 V70 with 290k miles
In past 6 months - New serpentine belt; new timing belt, new alternator, new dual-mass clutch
5 speed manual

High pitched sound begins after 10 mins of driving; sound quiets when gas on pedal accelerating but then resumes
Present while driving and idle.
Annoying sound

Is this a pulley bearing? Any way to test?

 

After the engine runs for the 10 minutes you mentioned, remove the oil cap on the engine. If the sound stops, perhaps you have a PVC blockage leading to a higher pressure than normal.

 

Auditory hallucinations? When I was pregnant with my youngest I would be awoken by either a dolphin sound or a doorbell ten times louder than any I’d heard before

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