Short-Term Stratified Temporal Noise Monitoring Strategies for Estimation of Day Equivalent Levels in Metropolitan City Delhi, India

Abstract

The present work analyses the accuracy of short-term noise monitoring strategies for estimating day equivalent sound levels (L_day or L_{Aeq,6 am–10 pm}) in Delhi city, India. The ambient noise monitoring data collected from 26 real-time noise monitoring stations, installed by Delhi Pollution Control Committee at distinct locations in Delhi city was utilized for the study. It was observed that average of randomly selected 1-h equivalent noise levels monitored in three sampling intervals in a day—06 am to 12 pm; 12 pm to 4 pm; and 4 pm to 10 pm, estimated L_day with an accuracy of ± 3.5 dBA with 95% probability. A dditionally, a stratified temporal sampling strategy for monitoring environment noise levels to estimate the day equivalent level for different zones was proposed with three stratified temporal intervals—9 am to 11 am; 2 pm to 3 pm; and 5 pm to 8 pm for commercial and industrial zones, and 9 am to 11 am; 12 pm to 2 pm; and 5 pm to 8 pm for residential and silence zones. It was observed that the day equivalent noise level can be estimated with an accuracy of ± 2.0 dBA for all the four zones with 95% probability if the noise levels are monitored for 1 h in each of three stratified temporal intervals. The present study may be helpful in conducting noise monitoring and mapping for a larger part of metropolitan cities of India, as continuous long-term (16-h) noise monitoring can be a quite cumbersome, time-consuming, and expensive process.