car engine noise
 

Hi, i'm new to this forum and not mechanically clued up on cars.
My Honda IVTEC engine 2000cc, 160bhp is making a weird sound after some acceleration(lots of gas etc)
Mechanic thinks its a bearing. Not sure what he means. I've checked power steering fluid which is fine. Is it the clutch release bearing or something else. car has done 25K mileage and engine otherwise seems sound. Has had good service history. I can't see it being engine since these engines last near 150k miles.

The sound is a humming sound/purring and is coming from near the fan belt. The belt is newish/not worn and is Ok. mechanic thinks its a bearing. Should it be changed urgently or can i leave it...I first noticed it around 6-8mths ago...so its not new symptom. It only occurs when car is hot not if its driven slowly...need hard accel to reproduce it.