Help with sound problem

[Tretzik]

I need help with a sound issue in a concrete block building with a steel decking and I joist roof system. There is a 4" concrete slab on grade floor. The problem is low frequency sound transfer to the adjacent space separated by a "soundwall" that was not engineered and just built by a contractor. The wall system is a 16' tall wall built out of metal 2x6 studs with 1/2 drywall on each side. To make it sound proof they built another 2x6 wall in front of the existing with a 1" space, insulated it and put up one layer of 1/2 drywall. The sound is from dropping urethane weights from overhead averaging about 275#. They are dropped onto 3" of vulcanized rubber mats on top of 3/4 plywood on top of commercial carpet. There seems to be very little vibration through the floor in the space where the weights are being dropped. The impact makes a very low frequency boom upon impact registering about 90db.
Is the current wall system sufficient? If not how should a new one be built? Since the floor vibration in space where the impact is occurring seems minimal how much sound could be transmitted through the floor?

 

[MiketheEngineer]

Stop dropping the weights or move out??

Sound proof the ceiling??

 

[hydtools]

The walls need more mass to stop transfer of low frequency boom. Hang lead-loaded vinyl on the source side of the wall. Add 3/4" drywall on top of the 1/2".

Ted

 

[GregLocock]

Or design a better impact system for the urethane weights.

Low frequency impact noises are very hard to attenuate, particularly if they are structure borne.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[SylvestreW]

The description isn't entirely clear to me but if the two rooms are adjacent, and share the same floor, then almost all the energy is likely from the floor.

I did a project a while back with a similar setup. Gym in condo on ground floor and 2 bays over were guest suites. Testing was showing most of the energy was transmitted through the floor structure and re-radiated.

This was with 25# weights dropped about 3 feet (despite signs all over the gym against this).

Do you have measurements prior to when the new wall went it? If so, you can see how much drop there was with the wall. Either way, to improve the wall, for low freq. requires mass, mass and more mass.

Otherwise, ease up on the weight drops.

 

[Tmoose]

"Testing was showing......"

I'd want confirmation of the path before modifying anything.

Can you hear the booming when on the roof?

Before bringing in an analyst capable of measuring impulsive sound and vibration, Is anything detectable with a finger tip (first with nail in contact, then fleshy tip) on the quiet side floor, the floor and living space edges of the sound wall, and the middle of the sound wall, and the concrete walls? Any detectable vibration of a large panel is potentially a problem.

Are the upper edges of the 2 walls supported independently?
What is the detail of walls meeting the roof? They ought to be sealed up with fancy caulk 100%.