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Having actually studied acoustics I can assure you it is the shape and the material as it pertains to absorption. However you can do better than the cartons with strategically placed comforters and or clothes closets in your recording space. More important is addressing your specific need. What is the point of our desire to acoustically treat your room?



Scott:

Your knowledge of acoustics obviously gets you to the correct answer (are egg cartons effective?).

I have an elementary acoustics background, so I approach this from an energy point of view. Considering that sound is a form of energy helps to understand the phenomenon. When a sound wave (alternating positive and negative air pressure) hits a surface, some energy is absorbed when the surface deflects under the pressure - softer surfaces absorb more energy than hard reflective surfaces such as glass.

Any soft surface that will readily deflect when the sound wave strikes it will absorb energy, and this will reduce the amount of sound energy reflected.

Another "energy trap" (which Scott understands better than I) are spaces in the surface of the material that a sound wave strikes. When some of the sound wave goes into the small spaces, it doesn't get reflected out immediately, but gets absorbed as it bounces off the soft surfaces. The deep recesses of anechoic chambers employ this strategy; not only is the foam soft, it's porous, and the deep recesses trap the sound energy enabling more of it to be absorbed.

In the Winspear Centre in Edmonton AB, the hard masonry walls are hung with heavy curtains that can be raised or lowered to adjust the reflectivity of the walls. With the touch of a few buttons, the motorized curtains can be accurately "tuned" to achieve the appropriate reflectivity for the music being performed. This is simply a sophisticated application of Scott's suggestion.

So it's not going to break the bank, but may take some time to get the desired result.

Glenn