TY  - RPRT
TI  - Letter Circular 632: sound absorption coefficients of the more common acoustic materials (supersedes Letter Circular 573)
PY  - 1941
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 632
DO  - 10.6028/NBS.LCIRC.632
ER  -