So manufacturers are installing these in new cars and i like the idea of it. Does anyone know how they do it?

İntake noise on most turbo cars arent as good as na's so id personally only do this on a non turbo.

Whats your thoughts?

The turbos have a good noise when the the turbo starts spooling. but i sure love the sound of a high revving N/A
 
not sure exactly how theyre done but theres a branch off from the intake pipe which leads into the cabin.
the toyota 86 has it.

Some manufacturers are "cheating" with this - I know the new Polo GTI has a mic in the engine bay, which replicates induction & engine noise through the car's stereo... Audi have it on the new S6 I think as well, with speakers in the headlining and utilising the massive surround sound stereo - theirs also does active sound deadening, so not only do you hear growl from the engine, but it can cancel out wind noise, tyre roar, and the crappy noise the engine makes when it shuts down 4 cylinders (unfortunately it still can't stop audi drivings sitting 1/2 a foot off your arse...).
 
Piping into the cabin is *just* ok  (I'm not a huge fan, but at least the noise is "real") but using stereos & mics to make it sound "better" is ridiculous. 

IF manufacturers made cars like they used to, they wouldn't have to do this. Nothing like the intense vibration of the interior panels and loud mechanical racket behind your ears when you rev the balls off the 3SGE :D

^ummm no...i actually wished my car didn't do that 
If i want NVH i'll just hop on the bike :P

A bit of a **** having the noise played through the stereo system.
What next? v8 and v12 sound options..
 
An amg cl55 drove past me walking to station.
Almost silent, then the guy gave a bit from the lights and the note changed to "feral" mode. Very nice ;p

Why stop there?
How about something like a V12 Ferrari synthesized sound, rev matched to your 4 cylinder motor playing out under the back of the car through a high powered amp and speakers?
Turn the volume upand down as you like, he he.

Lets not get off topic now, i dont want to fake the sound but more enhance it for myself in the car without making the car louder for everyone else.

http://www.youtube.com/watch?v=b9XAC-BvUyo
"enhance it for myself in the car without making the car louder for everyone else"
There's your solution LOL

Way to take half a quote there tree.