Jepp, you're right, but I the sound is pretty characteristic also without turbochargers, as long as it is inline 5 sylinder.
Here is another one, from a small hillclimb I use to visit every year not far from here, two videos of an Audi Sportquattro S1. The music is a bit too loud in the first clip, but you can still hear the sound pretty well.
wvideo_audi_s1.wmv
inboard the same car;
AudiS1.wmv

My post no. 100