The noise from the cars has been toned down lately, so it's not as noisy as it used to be,
That said, I think the F1 cars are due another noise upgrade for 2017 ??
I once attended the British Touring Car Championships at Brands Hatch (around 1994 or so i think), and we were stood right next to the starting grid.
When the lights started changing for the race to start and they upped the revs to many thousands, the noise, and the shaking ground was unbelievable. I remember my girlfriend looking totally startled, mouthing "OH MY GOD" and trying to hang onto something due to the huge amount of vibration through the ground.
It was a lot of fun.