It all depends on the body, the place, resonance and a number of factors. When I tested my M6TTLs against my M3 in my studio, the M3 came off as the quietest. Oddly enough, I checked them in my living room and the M6TTLs won this time. Why? Beats me, but then, any Leica will be quieter than any SLR 🙄 , and that's the thing that counts.