They are usually quieter at a constant throttle setting as on a motorway. Far more noisy under acceleration. As Nick points out the filter is just behind the bulkhead so you are pretty well on top of it. Depends how much you want the H.P. gain you get with one set up properly. K & N element in the standard housing whilst not giving as much as gain is more civilized.
It's been proved that a k & n element in the standard air box is actually better (quieter and more bhp) over the cone filters.
What Mr Calver neglected to do on this test is to use any kind of radius into the carb when fitting the cone type filters. The standard cast elbow that the standard airbox mounts to forms a smooth entry into the carb. When using the cone filter there is no such luxury unless you fit a radius/stub stack of some sort. I suspect if he'd done this the results might have been different.
Phil.
But then how many people do just bolt on a cone air filter and give it no thought or consideration...
