But, of course, I don't know if it is the same circuit
It certainly wasn't.
1972-1978 had the track in its 6'th generation, 13.640km long
First of all, there were no chicanes on the long Mulsanne straight, but the 3km section from Arnage to the Ford chicane was modified for the 1972 season, into what we now call the Porsche Curves. (i-e- Maison Blanche was no longer on the track).
The max average speed on that track was Renault Alpine A443 at 229 km/h in 1978, while the fastest Matra was Cevert in the MS 670B in 1973 at 223.607km/h
Fastest average (race-) speed of all time was not surprisingly set just before the Mulsanne chicanes were introduced in 1991, by the Jaguar XJR9 in 1989 - at 242.093 km/h (a Sauber Mercedes C9 did 249.826 km/h in that years test-weekend)
Today we're up to track incarnation 14, which is 13.629km long. Even with the two chicanes on the 7km Mulsanne-straight, and the longer and slower Dunlop complex, the winning Audi did 236.183 km/h on its best race-lap.
And the only sound you hear from that car is wind and tyres ... the Peugeot had a little engine noise, but nowhere near the wonderful Matra's. I think the Jan Lammers's ear-splitting "Racing for Holland" Dome from the last few years comes closest. :-)
The nicest sounding car in the pack this year is IMO still the Spyker ... definitely not the fastest or most reliable (sadly) but BOY does it sound great.
/Lennart