[Nasher]

Induction Roar is a bit of an acquired taste.

Replacing the standard liner under the tank will have a damping effect, but changes the noise rather than reduces the volume too much.

My M900 came to me with an open airbox top, and the tank lined underneath with Foil backed sound deadening/heat reflecting material. When I put a std liner back under it the induction roar became lower pitched, and blended in more with the Exhaust note from the DP Remus silencers, so although it was in reality almost as loud it definitely was not as noticeable.

My M1000 also came to me with an open airbox top.
The liner under the tank was really manky, actually mouldy, and split open in places spilling bits of foam everywhere.
I tried patching it up and persisting with it, but have definitely noticed a difference in pitch/tone now I've ripped it out and am looking for a replacement.

Note that on my M1000 I also threw away the manky unbranded 'Performance' Air filter and replaced it with a Genuine K&N one.
It's probably just because the old one was blocked up, but the Tone/Pitch went up again with the K&N.