I've run several different Ram Air setups on my car (all ones I designed), and the quietest one was a hose-fed setup (like the Olds W-30 style) using a couple handmade bumper scoops under the valence. The engine was VERY quiet around town, eerily quiet at cruising speed, and very muffled under full throttle. All the noise was contained in the enclosed air cleaner, routed through the hoses, and came out at the front of the car.
On a factory Ram Air setup, the sound of the carb "roaring" will come out the hood scoops. With a 360 open element, the carb roar is unrestricted. That's why the factory started using snorkel air cleaners, some with dual inlets, some with a tiny single snorkel. It was all for noise control. The 70-72 Trans Am's used an enclosed air cleaner, and were quiet, but when you floored it, the trap door kicked open and the carb noise was directed at the windshield, and it was loud (as in cool sounding!).
One of the most extreme cases (for me) on sound control was with a 65 GTO tri-power I had. With the 3 open air cleaners, the thing sounded like a freight train when you floored it. I installed a repro Ram Air pan, opened the scoop, and the full throttle sound was much more subdued.
As for performance, getting cool air to the carb will always provide more horsepower, but unless you jet up accordingly, you're just leaning the mixture out. What many people discover (me too) is that our Q-Jet jetting is always a tad rich, so on cold nights, the engine seems to come alive. Cold air is denser than warm air, so on each intake stroke, you can pack more air into the cylinder, making more horsepower.
Ram Air won't be very noticeable seat-of-the-pants, but it does provide more horsepower.
