Drumming / Vibration noise on bad road surfaces

[OriginalBigAl]

On poor road surfaces ( more so at low speeds ) there is a drumming /vibration noises from the rear which I had put down to the suspension not being able to cope with the higher frequency jolting and transferring non- damped vibrations into the chassis.
Today whilst washing the car , I aimed the hose pipe at the grey plastic insert in the bumper which contains the fog light and that produced a noise not dissimilar to that experience whilst in the cabin. Further investigation by tapping the panel with the ends of my fingers revealed that there was a hollow noise throughout the panel with the lower edge free to move which can vibrate and slightly chafe the black plastic. Even the false bumper bits had a lot of resonance which you would have thought through their shape were stiffer.
I now think that this might be the cause of the annoyance and when the weather warms up will try to remedy it with the application of some sound/ vibration deadening on the interior surfaces although the repair manual is not clear if this can be accessed by just removing the rear under bumper cover.
Will report back at a later date but until then give yours a two digit tap and see what you think?

 

[PerthPete]

Maybe some fixings need to be tightened a bit?

 

[OriginalBigAl]

Maybe some fixings need to be tightened a bit?

All the fixings for that panel are hidden , all will be revealed when I get the bottom panel off. At the moment its not that high up my priority list.