High Performance, Full Bandwidth Soundproof Walls

This is a sample of a residential grade full bandwidth soundproof wall. The wall, like all our walls is actually two walls. The inner wall is a flexible and very damped double layer sheetrock wall that is suspended off the other wall. This inner wall is the limp mass wall and it weighs about 5 to 6 psf. It is built to absorb low frequency energy when it moves. At 30 Hz it only blocks about 8 dB. But this leaf of the two leaf wall assembly is not intended to block deep bass. It is the sound absorbing part of the deep bass reflecting wall, which is the outer wall.

This outer wall is not built as a heavy wall, it is build as a strong wall. Typical wall construction might be 2x6 studs on 12” centers. The point of a strong wall is to minimally move under the low frequency pressure of bass tones and explosive transients. A number of proprietary features have been left out of this wall sketch but the basic principles as to how it works are covered.

In order for the deep bass to apply pressure to the strong wall, it has to first deflect the damped limp mass wall. This damped, limp mass wall is built and suspended in a particular manner so as it becomes what is known as a membrane bass trap. The entire surface of the room, typically about 1000 sqft of surface area, all except the floors, is built to act as a giant membrane bass trap. The deeper the air cavity behind the suspended damped limp mass wall, the better the absorption of the deep bass will be. Note the sound blanket which also damps, but in the mid and high frequencies.

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Copyright 2010 Acoustic Sciences Corp.