TY  - RPRT
TI  - Letter Circular 425: sound absorption coefficients of the more common materials (superseding Letter Circular 359)
PY  - 1934
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 425
DO  - 10.6028/NBS.LCIRC.425
ER  -