Experimental Feature |
Instrumentation for the field measurements consisted of precision grade sound level meter (according to IEC 651, ANSI S1.4 type 2 class standards), 1/2-in. condenser microphone and 1/3-octave filter with frequency range and measuring level range of 31.5 Hz–8 KHz and 30–130 dB respectively. The instruments were calibrated by the internal sound level calibrator before making measurements at each site. All the instruments comply with IEC standards. Details procedures for the environmental noise measurements can be found in Refs. [1], [2], [3]. LAi (A-weighted instantaneous Sound pressure level) measurements were recorded at intervals of 30 s for a period of 30 min, giving 60 m readings per sampling location. This procedure was carried out for morning (7:00–9:00 a.m.), afternoon (1:00–3:00 p.m.) and evening (6:00–8:00 p.m.) measurements. From these readings, commonly used community noise descriptors such as minimum noise level (Lmin), maximum noise level (Lmax), equivalent A-weighted sound pressure level (LAeq), Noise Pollution Level (LNP), Traffic Noise Index (TNI), Noise Climate (NC), Noise Emission Index (NEI), Day Noise Levels (LD), Night Noise Levels (LN), the exceedence percentiles (L10, L50, L90), Noise climate (NC) and Traffic noise index (TNI) were computed. |