abating sound transference from store to 2nd floor

[SohoOwner]

As owner of an old multiple-story building with wood joists, I rented out the first-floor store space as a furniture storeroom for years, and my 2nd floor tenants were happy.  The new store occupants are office workers and sound will be greater. The workers installed a drop-down ceiling with 1 5/8" metal joists and 1/2" sheetrock, but the acoustics seem same as before.  In fact the workers' "boom box" even seems to vibrate the hardwood floor above, and I don't think the situation has been improved at all.

Do we have any options left re:  soundproofing?  I'm reading here that cellulose can't do much if anything.

Acoustic 'hooks" were thought too expensive, and it's much too late to insist on them.

[Randy S]

They did not insulate the cavity???

If that is the case you might have to open the ceiling back up.

You could just add more mass, but most systems in the industry are testing with insulated cavities therefore the results could be extremely off if left hollow.

Randy S.
 

[SohoOwner]

Thanks, Randy, for the response.   No, they didn't insulate the cavity because I thought we already had adequate soundproofing with the old ceiling.  We thought if anything a second ceiling of metal furring strips and 1/2" sheet rock (installed for cosmetic reasons) would only improve matters.  But did leaving the cavities make it worse than otherwise?  Maybe we created an echo chamber with nothing but air between the two ceilings? 

Were you thinking that fiberglas batting would have been the way to go between metal strips?

Too late for removing the new sheet rock (they're already taping), but I could use the cellulose option.  A company that infused the front part of the store a couple of months ago by cutting small holes in the plaster and then covering them over. We did notice an improvement there.

I am struggling to keep calm.  Faced with a minimum of $1500 for professional testing awhile back, we tried to conduct our own test using a "boom box", sadly undersized by comparison with the workers' own noisemaker and maybe disastrously inadequate.  If I had the option back I certainly would have hired the professional for initial tests.  $1500 is nothing if it provides us with foreknowledge.

Please let me know if you think the cellulose option would or wouldn't be a waste of time at this point.  Now would be the time to hire them rather than later.

[Randy S]

Yes, You created the dreaded triple leaf system. At this point going forward the results will be questionable based on the noise source. When dealing with human speech frequencies the triple leaf is not so bad and cellulose might be an option but when dealing with lower frequencies all bets are off and your guess is as good as mine when it comes to results.

I am going to need you to contact me direct so we can discuss appropriate actions that would assist in greater reductions or bite the bullet and start over.

One of the things that flag this build is did you leave the original lath and plaster in the ceiling???

Call me! I am concerned I am missing some details.

Randy S.
760-752-3030 ext 3095