Wooden floors/stages and bass absorbtion

Does anyone know the technical reasons why this occurs and if there's any ways of mitigating it? Reinforcing the floor with more cross members to stiffen it up?

I presume its just due to the nature of the surface, it acts as a damping mass on the sound. But it can be especially pronounced in some places, especially when the speakers are on a stage or step at a height above the main floor.

My usual method is put some underlay down onto the wood then drop a load of concrete slabs or blocks down onto that, then bass bins on top. It stops quite a bit of transmitted vibration but the sound still doesn't couple with the floor the way it does on concrete or stone floors.

As i understand it all materials will have an absorbancy coefficant, solid stone walls and floors will reflect far more than thin less dence floors, id guess the wooden stage is absorbing and as bespoke said putting a heavy well straped stack together should help, much like extra bracing in subs. 

We have a local town hall venue that has an upstairs ball room with a wooden floor and an underpass directly below, they have recently soundproofed this floor and you defanately dont get as much bass as you used to. 

A typical wooden floor acts like 4Pi below 100hz of so.

Some floors are practically an ideal bass trap if it wasn't for all the noisy vibrating panels. A non-uniform wooden floor with gaps/loose panels, various sized cavities, possibly with underlay/insulation etc. would be great for damping room modes I'm sure, but I'd rather get a solid concrete box any day :P