Isolation Box Question

[Matt77]

I'm just finishing an isolation box.
I'll give the full details of this when finished tomorrow.
I'm very pleased with the result of the initial testing.
In the meantime can anyone answer the following question:

Which stops more noise 50mm of kiln dry sand or 50mm of heavy duty MDF?

[MDV]

Probably whichevers heavier.

I'd guess the sand.

[Oli]

The sand; it has better energy-absorbing properties- the MDF is likely to resonate and actually transfer a lot of the energy due to it being a heavily compressed, solid material. 50mm of sand covering a cab (even 1x12), is going to be very heavy though!