| Materials and Structure Testing:
Transmission Loss Testing
ISO-140 & ASTM-E90:
NWAA Labs tests for transmission loss using both the ISO-140 and the ASTM E-90 standards. This is a technique that compares the levels between one reverberation room where broadband noise, (ours is 142dB broadband), is present and another reverberation room, where the level of noise is very low, with a sample located in a common wall structure between the rooms. This data is then used to calculate an STC (Sound Transmission Coefficient) that can be used to compare other structures to each other. The results are then delivered to the customer as a detailed report along with a Chart and Graph of the coefficients.
Ron Sauro has been interested in advancing the ability to measure the acoustical parameters of materials that are used in construction. Transmission loss is one of those parameters and his interest has been to widen the frequency ranges that can be tested accurately. The "normal" frequency range in STC testing is from 100Hz to 4000Hz, but Ron has built this lab with the ability to accurately test in the frequency range of 25Hz to 10,000Hz. This frequency range has enabled NWAA Labs to be able to support ongoing research at very low frequency ranges with a "Confidence Index" of better that 95% at 25Hz. The transmission loss sample window is 10 ft 4 inches high by 12 ft 4 inches wide and has a maximum depth of 28 inches. The laboratory's exceptional flanking limits - in excess of 72 dB without compensation being applied at any frequency - allows us to test very high STC construction elements. Windows and Doors need to be mounted in a filler wall assembly that has at least a 20 dB higher STC than the unit under test. Clients who test at NWAA Labs can be confident that the difference in STCs between filler wall and test unit means the level measured is coming directly from their sample providing the most accurate results possible.
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