It's all relative. 80 decibels in the day isn't that loud. It's the sound of a vacuum cleaner. At night on the other hand 80db is loud. Considering that the F1 are 140DB the sound differences are massive.
These FE cars are MUCH quieter than their F1 cousins.
From http://trace.wisc.edu/docs/2004-About-dB/
So it's really 2^6 = 64x as loud, perceptually.
http://www.marca.com/2014/01/30/motor/formula1/1391085772.ht... (Spanish)
I grew up near a F1 track during the "big bang" turbo era (1,350+HP from a 1.5 litre engine that would only last 3 alps in qualifying trim)[1]. I'm pretty sure we'll never hear engines like those in circuit races again, and I'm not sure that's a bad thing.
[1] http://en.wikipedia.org/wiki/Formula_One_engines#1966.E2.80....