Community Noise Measurements in Los Angeles, Detroit, and Boston

Abstract

Quantitative descriptors of the noise environment have been obtained for 20 urban areas in Los Angeles, Detroit, and Boston. Measurements involved the acquisition of a 10-min noise sample once each hour for a complete 24-h day, and the subsequent analysis of each noise sample to obtain a statistical distribution of the A-weighted noise levels and the number and frequency of occurrence of discrete noise intrusions. We present the time patterns of various community noise descriptors, such as the 50% level, the energy mean, the Noise Pollution Level (NPL), and the Traffic Noise Index (TNI), for several of the areas sampled. These noise measures show considerable spread in average daytime and nighttime levels. When classified in three groups according to gross differences in exposure to motor vehicle traffic, distinct differences in daytime and nighttime noise patterns and in sources of discrete noise intrusions are apparent. The several noise measures (including the 1, 10, 50, and 90% A-levels, TNI and NPL), generally show high correlation among each other, with the exception of the TNI when it is calculated on other than a 24-h basis.