This thread is a great example of why NVH (Noise, Vibration and Harshness) are all lumped together. We, as humans, sort of perceive all of these things in a related way. As an example, if a suspension impact is really loud we all sort of cringe and exclaim "Dang!" when it happens even if the actual hit doesn't jostle the car or upset it that much. We associate "loud" with "rough". Rough rides or vibration often accompany noise.
Booming/Buffeting is a weird thing in these cars. It is often triggered by a suspension impact (washboard surfaces make it most obvious, whereas "single hits" are much less so). With this you get a combination of impact you feel (often minor), accompanied by the boom noise (big cabin/lots of glass for reflections/etc.) and (unfortunately) a pressure wave (the buffet). The latter is caused by a big surface "moving" up/down or in/out...like a speaker cone. The biggest surface in the Tesla is the hatch and, of course, it can move slightly. The somewhat erratic suspension firmness of the Teslas (whethere because of part number changes, too much sensitivity to oil viscosity in the dampers or whatever) simply exaggerates and triggers the booming/buffeting. As a bonus, some people are simply more sensitive to the latter. In the same car one person will declare it to be fine and another will say they can hear/feel it. If you can reduce the movement of the hatch, you may reduce boominess/buffeting and thus "feel" like the car is riding more smoothly (in fact, it is just less NVH over all).
Finally, this isn't a Tesla unique phenomenon. The current generation of GM's full size SUVs are absolutely plagued with the booming/buffeting. There are posts out there with thousands of replies in them from owners suffering with this. Many folks are getting buy backs. GM has issued a number of attempted fixes. The first involved reinforcing/repairing the roof bows under the headliner as the theory was the new thinner sheet metal (for weight savings) was flexing in an out (like an old oil can). Some report some level of success, but many do not. The current attempted fix involves welding weights to exhaust clamps and positioning the clamps at various points along the exhaust pipe to try and dampen any vibrations that are being introduced into the cabin. The vibrating exhaust is made worse by GM's fuel saving "4 cylinder" mode on the V8s which is less smooth. The "real" fix is a stiffer structure, but GM doesn't appear to have a ready answer for this (short of a redesign). A nightmare for many of these owners...they've even managed to get news coverage on this issue. Not good.
BMW owners experienced the phenomenon in the E90 generation 3 series convertible with the hard top. BMW tried to solve that problem by injecting epoxy into every nook and cranny in the hard top. Most owners reported the issue "improved", but wasn't solved. And yes, I've done a bit too much research on this.
