Not at all. The compressed surface is smooth and non-absorptive an so reflects sound.
Here is part of the description from GIK:
"The GridFusor© is made from EPS (expanded polystyrene) so it’s light enough easily mountable on walls, ceilings, etc. without the use of damaging adhesives or massive mounting holes while still providing excellent diffusion characteristics.
Incorporating a mirror-imaged pair of 13-root diffusors, the GridFusor© provides excellent diffusion from 600 Hz to 5,000 Hz and additional scattering below and above the diffusion range. The GridFusor© is light enough that no additional support is required for your existing ceiling grid and it’s light enough that insulation above can still provide broadband bass control."
I tried a carton as it represented an “inexpensive” way to experiment with some diffusion in different parts of my room… $214 for four 2ft x 2ft square panels vs $600 (and up) to duplicate the capabilities in wood construction. It’s a really, really clever idea if you are dealing with a drop tile ceiling in a basement room. I’d be all over this stuff if I was in that situation, as you wouldn’t need touch them once dropped in place. But they are a tad too fragile to stand up well to repeated repositioning and manhandling.
More info here: http://www.gikacoustics.com/product/gik-acoustics-gridfusor/