Long-time trends in ship traffic noise for four sites off the North American West Coast

Measurements (1994-2007) from four cabled-to-shore hydrophone systems located off the North American west coast permit extensive comparisons between "contemporary" low frequency ship traffic noise (25-50 Hz) collected in the past decade to measurements made over 1963-1965 with the same in-water equipment at the same sites. An increase of roughly 10 dB over the band 25-40 Hz at one site has already been reported [Andrew et al., Acoust. Res. Lett. Online 3(2), 65-70 (2002)]. Newly corrected data from the remaining three systems generally corroborate this increase. Simple linear trend lines of the contemporary traffic noise (duration 6 to 12+ years) show that recent levels are slightly increasing, holding steady, or decreasing. These results confirm the prediction by Ross that the rate of increase in traffic noise would be far less at the end of the 20th century compared to that observed in the 1950s and 1960s.     

Synthesis and Properties of New Polyphenylquinoxaline-imide-amides

Abstract

New thermostable polymers containing imide and phenylquinoxaline units have been prepared by solution polycondensation of diaminophenylquinoxaline coupled by ether, methylene, or sulfone linkages with diacid chlorides containing preformed imide rings. Solubility, thermal stability, and electroinsulating properties of these compounds are discussed and compared with those of related heterocyclic polymers previously reported.