Using heavy material for equipment racks does have some acoustic benefit rooted in physics, but using solid material like marble also presents risks if used alone. The theory of using heavy materials is termed mass loading. Adding mass increases inertia, an objects resistance to change in motion. The equipment rack will become more resistant to vibrations from the floor and air because it becomes harder to set into vibrational movement.
All materials have a resonant frequency - a frequency that easily sets the material into vibrational movement. Mass loading also is used to move the resonant frequency outside of the audible range and providing damping of the energy.
Marble provides a solid flat surface for coupling equipment to the rack so vibrations from the equipment are transmitted to the rack.
So why does marble alone fail in theory? Vibration travels through solid material easier than liquids, liquid easier than gas. The marble will be subject ringing and resonant frequencies, and easily transmit the ringing to the equipment by coupling. This will be audible most probably as muddling detail and high frequency distortion. Most equipment racks that use mass loading will use sand, which acts to present the befits of mass loading while also having “liquid” properties to effect changing the resonant frequency and damping.
The best vibration management systems combine the use of mass loading and damping.
