Apparently there's a huge backlash concerning the new sound of F1 and though it is pretty much established that evolution = F1 and it is not the show that should define Grand Prix racing, the audio experience of Formula One has been on a downward spiral since Ferrari bid farewell to its V12 engines at the end of the 1995 season.
All of those looking for some screaming N/A sound in open-seaters must be highly disappointed in F1, so here are some series you should check out in need for ear protection as a must.
Auto GP should be one of the best sounding series currently, a bit like F1of 2013 with a slightly lower rev limit. 3.4-litre Zytek V8 engines for the rescue. You can find it on EuropSport
Formula Renault 3.5 uses almost almost Zytek engines to the ones in Auto GP, only the cars look much nicer (something like an F1 car around 2004) and mainly sponsored by the same companies as F1, sou you'll get your Lotuses, Red Bulls, Caterhams, etc. Your choice of F1.
Something you won't catch on TV, but BOSS GP is probably the best ever racing series on Earth. "BOSS" stands for Big Open Single Seaters, and it is basically a Formula Libre thing with former F1, Champ Car, GP2, Formula3000, etc. cars lining up at the start line. Here's another video to convince you:
To get your fixture, visit their website: http://bossgp.com/
EDIT: I totally forgot to insert Formula Nippon as I got wound up watching mixed class of cars running around at Monza. Formula Nippon is ultra-cool because the cars sound like F1 ones, and look like CART vehicles from the nineties, with an added fugly front wing: