My buddy has a venue and has neighbors that are getting a little fussy with the subwoofer kick thumping. I'm looking for someone in the Southern California area that can help consult with them on what needs to be done to get their exterior sound bleed under control.
Was considering suggesting a cardiod sub array, but not sure if that will really help.
Hit me up via PM or feel free to reply on here
Josh Billings
In the 80’s I got tired of being called by the police in the middle of the night when we were doing life testing of the Servodrive subwoofers at Intersonics. It only took a few trips in the middle of the night to shut it off before a solution was imperative.
Some solutions have been described already but this might be helpful too.
Obviously sound is pressure, pressure which alternates positive and negative and at say 132dB, this represents an alternating peak pressure of about 2 pounds per square foot of area. This force is felt by say a wall and it is the walls mass and stiffness and the duration the pressure is applied that determines how far that wall will move in and out in response. That movement-radiates the attenuated sound on the other side.
There is a complication too, stiffness and mass are opposite reactive forces and when paired as in a wall (or a loudspeaker cone in a box), one also has a resonance or resonant frequency. As in other parts of audio, the sharpness of that resonance is the Q and by adding things which have mechanical resistance (like drywall, construction adhesive etc) the Q of a resonance can be lowered / broadened.
In a room a diaphragm like wall resonance usually produces a suck out and not a peak as instead of a ridged boundary, it has give and losses. The “limp mass” mentioned reduces the stiffness and any significant resonance but increases the mechanical losses so that the act of simply moving the barrier dissipates a lot of the energy.
Another approach that works higher in frequency is various densities of fiberglass panels, these have a large amount of acoustic friction on the pressure as it propagates through it.
Anyway, at Intersonics we made a “death room” which had about 35dB of attenuation at 40Hz and lots more above and that ended the police calls and late night trips to shut it down.
It was a basic design I took from a sound control handbook and it went like this.
The header and footer was a 2x6, the studs were 2x4’s that were alternated so that the inside and outside walls were not connected other than at the top and bottom. The 2x4’s were covered with ¼ luan (cheap) plywood glued to the 2x4’s and then 5/8 drywall inside and out glued and screwed. The roof was the same construction and basically set on top like a cap and under the footers and between the roof and walls was carpet as a seal.
There was a 90 degree L aluminum in each corner top to bottom and the door had the same construction and sealed with foam tape and carpet. To make it nicer for testing non-subwoofers, we hung heavy shag carpet on (spaced just away from) the walls.
In your case, you might want to play band passed pink noise and go outside and see if there is a “hot spot” on the building that could be treated on the inside with a similar or other barrier.
Hope that helps
Tom
I should have mentioned a couple other things too, the warehouse building that the sound was leaking through and disturbing neighbors was cinderblock with red brick on the outside and while the test was running, you could clearly feel the wall. In a simple building, the large open spans of wall and ceiling are where the movement usually is as X dB = X pressure per sq foot.
Also, the sound room / barrier construction I mentioned is actually a lossy 3 element acoustic low pass filter and the electrical analogue might be considered to be an input parallel C (mass), a series L (the air between the walls as a spring) and a parallel C (mass) on the output. The 35dB attenuation at 40Hz is a lot, a reduction of about 3000:1 in energy.
