Stiffness increases by building the equivalent of another beam in the middle of the joist system (as presented in the drawing). Also, the additional load spreading will distribute the load among several joists. This alone may increase stiffness enough to resolve the structural deflection and low frequency footfall noise issues. We recommend stepped blocking as the first approach in resolving low frequency footfall noise transfer.
The blocking should be one size smaller than the framing, glued and nailed at each connection. Install blocking at the mid point for spans greater than 10′, at one third points for spans greater than 18′, and at one quarter points for spans greater than 25′.