Can anyone ID this engine noise? Audi A3 Sportback 2006

In recent months I've noticed more engine noise than before.
I can't seem to pinpoint it but it seems to come from the drivers side lower engine section. Perhaps a very slight rattle and some kind of friction noise when acelerating?
It's a 2006 A3 Sportback with 104,000km/64,000 miles and full Audi service history.