Noisier on occasion: On chilly mornings, the 4C is a creaky and noisy bugger. Seats, dash, and seemingly everything is jostling for your ears' attention.
If warm and on decent roads, the tires (while no autocross glue balls) are still sticky enough to grab dirt, sand and grains of stuff and fling it all into the tub.
It's a racket. You can hear the injectors firing, but the whole direct injection mechanism/compressor in particular is noisy. The transmission competes for noises and clunks without apology.
Some days, my seats have a low frequency moan and groan.
I once sold a boat with a 502 cubic inch engine (8.2 liters) that was in prime condition, and no explanation in the world ever made the Honda Civic driving kid that bought it understand that it is PRECISELY as is should be when it comes to making a racket. He had no idea what 8.2 liters of worked up engine sounded like, and he called me every weekend for a summer scared to death of the racket.
If you're under warranty, drive it and get to know it, then you'll start to notice patterns and it is the deviations that become important. But get with others who have 4C experience, or get your dealer tech's mobile number and call him every week for assurance!