As a general rule adding fairings to bicycles tends to do the opposite of making them quieter. But it might keep the wind off your ears...
My Quest has a windscreen, which does deflect a lot of the draught, but neither is it a full canopy. I have ridden with such, and the difference is surprising: what you lose in wind noise you gain in local resonance and heat.
Curiously enough, it's only when I ride my Quest that I wear earplugs; I use Doc's Pro Plugs. The need arises partly because velomobiles are both low to the ground and fast, and partly because I was fed up with the noise from the traffic that passes me at 50mph on the country roads that form half of my commute. I've come to realise that bus engines are also incredibly loud.
I first used Pro Plugs when riding my motorbike, but for that activity I soon graduated to Alpine, and then custom moulded ear plugs from
Ultimate Ear, to get the attenuation I wanted. The Pro Plugs don't really bear comparison: they're thin and off-the-shelf, but they take the edge off enough.