A/V RoomService Ltd. - Sound Clips

Wall Cavity Hits

A conventional wall, ceiling or floor assembly not only does a poor job of controlling noise between rooms. They also distort sound quality due to the assembly’s natural construction resonances. For example; a typical 8’ foot high 2x4 wall will resonate around 70 Hz. like a drum. Try hitting your wall with your fist between studs and listen. These cavities act like capacitors that store and release energy. Whenever the resonant frequency, or its harmonics are played into the room, the cavity sympathizes and plays back those frequencies into the room latter in time. This results in the room sounding slow and muddy.

On the other hand, too much mass, such as cement blocks, may be good for noise control, but lack low frequency absorption, allowing bass to reverberate in the room. This also makes for a slow and muddy reproduction. Well-engineered shell construction consists of a controlled balance of mass and absorption.

1. Fist hits to a cement block wall.
2. Fist hits to a typical residential wall (empty cavity, gypsum/wood 2x4/gypsum construction).
3. Fist hits to an acoustically treated wall system.

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