The noise level is only slightly higher and mainly due to induction sound (suction of air) and not particularly exhaust sound.
The main purpose of this conversion is to shorten the intake path to the throttle and thus lower the resistance to the air flow.
Don't forget that the filter box, situated behind the radiator and the long metal intake tube are getting hot, being close to the engine, so the cold air aspirated through the filter box and intake tube is heating up rather quickly.
Besides, the space around the intake manifold seems to be the coldest place in the engine compartment.
