What can I do to quiet the rumble?

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We have two problems in the same room.

Problem one is transmission of unwanted sound from the booth above the auditorium.

Problem two is the echo in the hallway of the unwanted sound from above.

Solutions for the first problem, I have been told, are to add more mass and stiffness to the floor under the platter. Could a layer of 1.5 inch plywood help? Or could the plywood be laid over a layer of acoustical material that would help isolate the rumble?

Solutions for the second problem have been suggested as to carpet the walls with acustical carpet? One person said that that wouldn't cut down the noise much. Or to use acousitcal panels covered with cloth, held off the wall a couple of inches to create a sound trap?

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I had VERY good results with a few of their Red Line pads used to isolate a monstrous Spencer Turnbine blower (not in a booth, isolated from transmitting to the slab).

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Carpet on the walls gets nasty. Acoustical tile gets chewed up fast in mechanical rooms. Standing acoustical tile off 1" or more basically only adds bass traps, so you'll need to decide if that's what you need. Sonex will gobble up room noise (except lowest freq's, you'll need to create bass traps for that), but it's expensive. There's some Sonex-knockoff sheets in the Holy Grainger Catalog under Acoustical Foam, but it's still not cheap.

Wall treatments (like Sonex) do almost nothing to reduce noise transmitted directly to the ceiling, wall, or floor.

If the problem is really horrible transmission through the floor, lay a new isolated floor on top of the old one. It may wind up being cheaper than Sonex & isolation pads.

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I'm not sure what you mean about sound in a hallway. Do you mean a hallway leading to the booth, or a hallway (down below) leading to the auditourium?

If the hallway is in or leading to the booth, and you want to kill some of the (higher freq) noise from the booth, maybe you could make some free-standing panels. Get or make some of those panels like they use to make office cubicules and just "wall-off" the area on each side of the projector and/or platter. Maybe a panel about 4ft x 8ft. Buy some 2x2's to make a frame and glue or nail some acoustic ceiling tiles to it. Either free-standing, or bolt it to the front wall so it could be removed to get more room when servicing. Recording studios use something like that to localize each instrument or singer, while allowing all the artists to see and hear each other.

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So with the specos rumbling, which i have the same problem, the platter itself is absorbing the rumble, and with nowhere to spit it out, it sends the noisy vibrations into the floor (we have the same setup I believe).

The rubber pads should do the trick and absorb a good portion of the vibrations. You should still look into filling the void in your floors with insulation to remove the rest of the noise.

Then again, If i had taken a career in mechanical engineering, you know, like desiging platters and projectors, well digital cinema would probably look pretty good. Damn good thing I am nothing more than a movie jockey.

Than again I could be wrong.

This should eat up most of the vibrations.

Then again, I am just a film junkie, what the hell do I know?