wierd question

[76bonanza]

My truck is lowered with springs in front 3 inch and cheap shocks. When I drive slow and turn I can feel a slight thumping in the floor. Nothing is hitting it and it is not rubbing. Now mind you the floor is just carpet no insulation of any kind. And I know slow truning puts the most strain on the suspention. is it just vibration from the frame and suspension I am feeling? The cab mounts are not that great either. If I move my foot down to flat part of floor there is some insulation and I feel nothing. (as a side note I can feel the bass from my generic speakers in the floor also).

Thanks