You don't find much formal testing on this because the entire phenomenon occurs below the 125Hz cutoff for STC calculations.
This topic is covered in some detail here: http://www.soundproofingcompany.com/...e_leaf_effect/
Essentially you want to build a wall, ceiling or floor with as low a resonance point as possible. Why? because we can't stop much vibration below that partition's resonance point. Above the resonance point we have the ability to reduce vibration. At and below the resonance point we are simply mass/stiffness defined. We get no help from decoupling, insulation, Green Glue, crucifixes or crossed fingers.
So if a wall has a resonance point at 100Hz, it will start to bleed sound as we approach 100Hz during music playback. At 150Hz, you can feel the wall start to vibrate. At 120Hz, much more vibration. At 100Hz, it's vibrating like crazy, and not stopping much sound at that frequency. Below 100Hz, things aren't very pretty, either. We'd therefore like that resonance point as low as possible.
How do we lower that resonance point? The #1 thing you can do is to decouple the wall surface. Decoupling will move a wall's resonance point down considerably. What else can we do? Add absorption (insulation) to drop even further. Then make the wall as heavy as possible with drywall. Lastly, we make the wall cavity as deep as we can. Each of these things will progressively march that resonance point down, down, down.
So decoupling becomes a fantastic weapon against low frequency. Without first decoupling, the benefits of mass, insulation and cavity depth are not fully realized.