Bass Proofing: The Big Problem in Soundproofing

When we began our work in soundproofing, we were working on audio rooms that contained some of the most powerful sound systems of the day. The big problem then remains the big problem today. How to bass proof a room. Back then we thought like everyone else that heavier walls would solve the problem but it just doesn’t. Normal stud frame construction can’t support the weight of a wall heavy enough to stop 30 Hz bass. According to the mass law, 1/8th inch thick lead sheet which weighs over 8#/sqft, will only provide 13 dB soundproofing at 30 Hz, which is right in the middle of the subwoofer range of 20 to 40 Hz.

The mass law says every time we double the weight, we raise the soundproofing by 6 dB. We can double the weight and raise the soundproofing level by 6 dB. At 16 psf we have 19 dB soundproofing. At 32 psf we have 25 dB soundproofing. The threshold of hearing at 30 Hz is 65 dB. This means if we have 100 dB in one room with walls that weigh 32 psf, we will still 30 Hz bass at a level equivalent to 25 dB, a distant but audible whisper.

A ½ inch thick lead wall weighs 32 pounds per square foot. If it is 8’ tall. It weight 250 # per lineal foot of wall. In most rooms there is about 70 lineal feet of wall. That is a wall weight of 17,500 pounds, the weight of 3 heavy cars. And if we add 300 sqft of ceiling to this, we have a total of 25,000 pound room, without mentioning the steel structure that is required to hold this room up. One good thing about using lead is that it is one of the few materials that contain its own built-in damping compound. Not only does it block bass but it absorbs bass energy out of what ever movement does take place. This is why we use lightweight strength not weight to block bass.

ASC understands the practical limits of materials in their use for soundproofing and use only the sensibly useful frequency range of each type of sound barrier used to provide the soundproofing.

Copyright 2010 Acoustic Sciences Corp.