loose change sound from the rear

[pvn]

Hello.

When driving over bumps I can hear from back (trunk) a sound which my best description would be: loose change or gold chain jumping on the metal floor in the spare wheel compartment. Imagine you hold a gold chain in your hand and toss it up and down. It is pretty the same noise. I even put my wife with a flashlight in the trunk, but she did not find the source of the noise. Needless to say I toke out everything from the trunk, but the noise is still there. The noise is more noticeable when I put down the rear seats. Something is definitely loose but I can not find it.

I have this problem from very long time but did not pay so much attention. But now after fixing some rattles and creaks it looks like this is the last one and I want to be a 100% rattle-free. I have searched the entire Internet about this and it seems I am not the only one with this problem. I have found 2010 TSX owners with the same problem, but no solution. I found two TSX TSBs (B09-014 and B09-019) with a similar symptoms but I do not think they are quite the same. I do not think the words "clicking" and "popping" apply to my "loose change/gold chain" sound.

Do you have any idea what could be the problem? Thank you.