could you find out if this comes from the car itself?

if it comes when the car gets some shocks to absorb then it could be the bearing of the suspension or some bearing of the chassis, wheel bearing or whatsoever... try to find out if this sound happens when driving to some holes or if the suspension has to do a lot of work... if so speak to a mechanics - maybe to the nissan-factory if it's a known problem.

well - it can't be that the bass causes the same sound as the suspension does - except if thats just a part in the car coming to vibration at a special frequency.
try to find out from where this vibration comes. this can be a very difficult thing... it can be somthing behind the dash - maybe some cables or screws or whatever.. you'll need some luck on finding the reason...