Have had a strange ticking noise for a month or so while driving the car, bit like the noise you would get by holding a piece of card in a bicycle wheels spokes.
Thought it might be tappets but the noise seems to stay the same if I dip the clutch and coast with engine rev at idle, so unsure if its drivetrain.

Car has been in for full service including gear and diff oil change (on monday) and it wasn't picked up on (wife dropped the car off and didn't mention it to the garage )

Any ideas folks? car is an 03 blob WRX with 78k on it.

 

Just an idea.

Check your spark plugs. i had a ticking noise for a couple of weeks which i thought was piston slap, until i wiggled 1 of the plugs and the noise stopped.

 

Headers, exhaust, up or down pipe leaking.

 

Have you checked your tyres for trapped stones or a nail/screw in them?

 

Thanks for the replies guys, no it isn't a stone. I have thought that it could be spark plugs, was hoping that they were going to be replaced on monday but they weren't touched. Guess that'll be the first thing to look at, had wondered if it was blown manifold gasket as well.
Can only really hear it when I'm going 30-40mph. Any quicker and engine revs and road/wind noise makes it inaudible. Doesn't get any more noticable with higher revs either.