New timing belt noise
 

I had the timing belt changed (plus water pump) because it was due (10 years old). I noticed straight away pulling away from the garage that the engine sounded different - there was a kind of high-ish pitch turbine-like whine. Not loud or what I'd call alarming - just annoying. I went back to the garage and they said it was fine - the belt was correctly fitted.

So I took it to another garage for a 2nd opinion. They heard the noise but said it was nothing to worry about, it's just because it was new.

Do you think the noise will disappear? Do belts 'bed in' or something?

if the noise is from the belt area .
i would look at it another way , if i was fitting a belt /pump .
no noise before it was fitted and once a new belt fitted i get a whine , my first thought would be faulty bearings or pump .
but first i would remove the alternator/aux belt then start the engine to see if i still have the noise if i do then i would have the timing belt cover off and investigate ,
if the noise has gone then start looking around the aux belt for the problem

I don't know what engine you have but if it's a D5 then replacing auxiliary belt is just as important as replacing the timing belt. When the aux belt snaps on these engines it tends to be thrown into the timing belt which will cause serious and expensive engine damage.

It's a 1.6D. The work was done at a garage, using a replacement 'kit' that I assume comes with all the necessary/advised parts to change (tensioners etc). Ditto the water pump. So I don't know in detail what was/wasn't replaced.

I've had the Cambelt/Aux Belt and Water Pump changed in one operation on our 3 cars:

Volvo = Whine afterwards (Volvo Water Pump used)

Citroen = Whine afterwards (Citroen Pump used)

Renault = No Whine after

I don't know the reason for it other than the Cambelt Kits were perhaps different to the original factory fit.

I must say that the whine is more at high revs say ~ 4000rpm +