In general, the pyramids are better at diffusing sonic anomalies than their wedge counterparts. By having 4 sides exposed, as opposed to 2, sound absorption is reduced while sonic accuracy is heightened. Pyramids will produce a much richer, more complete sound than wedges. Go with the larger sizes when battling against the undesirable sonic effects that bigger rooms pose. The Noise Reduction Coefficient (commonly abbreviated NRC) is a scalar representation of the amount of sound energy absorbed upon striking a particular surface*. An NRC of 0 indicates perfect reflection; an NRC of 1 indicates perfect absorption * In particular, NRC is the average of six sound absorption coefficients of the particular surface at frequencies 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz. These frequencies encompass the fundamental frequencies and first few overtones of typical human speech. Therefore, the NRC provides a decent and simple quantification of how well the particular surface will absorb the human voice.
