TY  - RPRT
TI  - Letter Circular 452: sound absorption coefficients of the more common materials (superseding Letter Circular 425)
PY  - 1935
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 452
DO  - 10.6028/NBS.LCIRC.452
ER  -