Paul D. Joppa
Boeing Commercial Airplane Group, P.O. Box 3707, MS 67-ML, Seattle, WA 98124-2207
Louis C. Sutherl
Rancho Palos Verdes, CA 90274
Allan J. Zuckerwar
NASA Langley Res. Ctr., Hampton, VA 23681-0001
A simple method for computing the attenuation due to atmospheric absorption for fractional octave bands of noise, outlined in a previous paper [P. D. Joppa, L. C. Sutherland, and A. J. Zuckerwar, J. Acoust. Soc. Am. Suppl. 1 88, S73 (1990)], is briefly reviewed and example applications to aircraft noise and room acoustics presented. The method uses an analytical approximation of a ``representative'' frequency for which the pure-tone attenuation loss due to atmospheric absorption is equal to the actual loss for the band of noise. The resulting total band attenuation, (delta)Lb for propagation over a distance s, for a band with an exact midband frequency f[sub m], is equal to a nonlinear function of the total pure-tone attenuation a(f[sub m])(centered dot)s over this path where a(f[sub m]) is the pure-tone attenuation coefficient at the exact midband frequency f[sub m]. The method provides better estimates than in SAE ARP 866A for the true band attenuation when the total true band attenuation is less than about 50 dB. For application to room acoustics, it is shown that the ``distance'' s involved is simply equal to the reverberation time, T times the speed of sound in the room.