You can judge a foam’s absorptive effectiveness by studying its NRC (Noise Reduction Coefficient), a single number average of a foam’s absorption in what was determined long ago to be the most important range. The federally mandated test (ASTM C423) is standardized to cover frequencies between 125Hz and 4000Hz, but when calculating an NRC, only the coefficients from 250Hz to 2000Hz are used to help alleviate the possibility of testing errors.

All of our foam products are tested at an independent, unbiased acoustical laboratory – the oldest, most reliable lab in the country. We insist on using only the very best testing facility because we believe our customers deserve the most accurate absorption coefficient information possible.

	125Hz	250Hz	500Hz	1KHz	2KHz	4KHz	NRC
1" Studiofoam Wedges	0.10	0.13	0.30	0.68	0.94	1.00	0.50
2" Studiofoam Wedges	0.11	0.30	0.91	1.05	0.99	1.00	0.80
3" Studiofoam Wedges	0.23	0.49	1.06	1.04	0.96	1.05	0.90
4" Studiofoam Wedges	0.31	0.85	1.25	1.14	1.06	1.09	1.10
2" Studiofoam Pyramids	0.13	0.27	0.62	0.92	1.02	1.02	0.70
4" Studiofoam Pyramids	0.27	0.50	1.01	1.13	1.11	1.12	0.95
2" Studiofoam Metro	0.13	0.23	0.68	0.93	0.91	0.89	0.70
2" SonoMatt	0.13	0.27	0.62	0.92	1.02	1.02	1.05
2" Studiofoam Wedgies	0.15	0.21	0.70	0.99	1.05	1.05	0.75
2" DST-114/244	0.16	0.29	0.57	0.75	0.90	1.00	0.65
MAX-Wall Panels	0.81	1.02	1.06	1.05	1.02	1.02	1.05
VENUS Bass Traps	1.63	1.34	1.29	1.26	1.25	1.20	1.30
LENRD Bass Traps	1.30	1.55	1.53	1.48	1.48	1.51	1.50
2" SonoFlat	0.27	0.60	1.17	1.06	1.02	1.02	0.95
Sunburst Males	1.08	1.23	1.14	1.07	1.05	1.08	1.10
Sunburst Females	0.65	1.02	1.00	1.08	1.05	1.08	1.05

STC Data Table

STC (Sound Transmission Class), is a numerical rating of how effective a material is at blocking the transmission of sound through itself. This rating generally applies to hard materials like rubberized sound barriers, concrete, brick and drywall but also applies to a much lesser degree to softer materials like mineral fiber (although it isn’t tested by itself; it’s tested as part of a wall system to verify its effectiveness). Virtually every material filters out some of the sound that travels through it, but dense materials are much better at this than are spongy materials.

**Sheetblok**
Center Frequency	Transmission Loss
125Hz	17
250Hz	17
500Hz	22
1000Hz	27
2000Hz	32
4000Hz	38
Overall STC = 27

Diffusors spread sound evenly over the entire hemisphere in front of it in both directions. The smoother the arc the better, because deviations from a smooth arc indicate volume changes. The object of diffusion is to redistribute mid and high frequency sound evenly throughout a space, not to absorb it, so you want a diffusor whose arcs at the various frequencies: (a) are very smooth, and (b) all show basically the same shape, which indicates the unit is providing uniform diffusion at all frequencies.

Diffusion Testing Data for GeoFusor & T'Fusor