Question for MT Owners

lately in NewEngland it's been cool early am and so the windows are closed - quiet ; leaving our condo complex there's a slight downhill for a short time & while in neutral I hear what I can only best describe as a very quiet downshift type sound - definitely not tire or so called road noise.

if anyone has a few moments to spare and could try this with their MT in neutral , I'd be interested in hearing the outcome - just wondering if it's normal BMW or not .

by way of comparison we also have an old '97 VW Jetta and in a similar test we only hear tire , i.e road noise.

thanks in advance for anyone that gives some feedback on their experience - BTW it's an '08 X3.