proposed integrated complex for delhi judicial academy

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Rapid Environmental Impact Assessment (REIA) Study for Proposed Integrated Complex for Delhi Judicial Academy, National Law School, and National Institute for Mediation & Conciliation at Dwarka, New Delhi the A weighted Scale which is measured as dB (A). This is more suitable for audible range of 20 to 20,000 Hz. The acoustical environment varies dynamically in magnitude and character through out most communities. The noise level variation can be temporal, spectral and spatial. The residential noise level is that level below which the ambient noise does not seem to dropdown during the given interval of time and is generally characterised by unidentified sources. Ambient noise level is characterised by significant variations above a base or a residential noise level. The maximum impact of noise is felt on urban areas, which is mostly due to the commercial activities and vehicular movement during peak hours of the day. Measured noise levels displayed as a function of time provides a useful scheme for describing the acoustical climate of a community. Noise levels recorded at each station with a time interval of about 30 minutes are computed for equivalent noise levels (L eq ). Equivalent noise level is a single number descriptor for describing time varying noise levels. L eq is the equivalent continuous sound level that is equivalent to the same sound energy as the actual fluctuating sound measured in the same period. This is necessary because sound from noise source often fluctuates widely during a given period of time. This is calculated from the following: L day is defined as the equivalent noise level measured over a period of time during day (6 am to 10 pm). L night is defined as the equivalent noise level measured over a period of time during night (10 pm to 6 am). A noise rating developed by Environment Protection Agency, USEPA for specification of community noise from all the sources is the Day-Night Sound Level, L dn . The noise rating developed for community noise from all sources is the Day- Night Sound Level (L dn ). It is similar to a 24 hr equivalent sound level except that during night time period (10 pm to 6 am) a 10 dB (A) weighting penalty added to the instantaneous sound level before computing the 24 hr average. L eq = 10 log 1/T N i=1 Ti (10) Li/10 Where, T = total time of sampling, Ti = Time duration of ith phase N = Number of phases Li = L eq for the ith phase This night time penalty is added to account for the fact that noise during night when people usually sleep is judged as more annoying than the same noise during the day time. 68
Rapid Environmental Impact Assessment (REIA) Study for Proposed Integrated Complex for Delhi Judicial Academy, National Law School, and National Institute for Mediation & Conciliation at Dwarka, New Delhi The L dn for a given location in a community may be calculated from the hourly L eq , by the following equation. L dn = 10 log {1/24[16(10 L day /10) + 8 x 10(L night +10)/10)]} Where, L day is the equivalent sound level during the day time (6 am to 10 pm) and L night is the equivalent sound level during the night time (10 pm to 6 am). In order to assess the ambient noise levels in the study area, monitoring was carried out at five different locations within the core zone of the study area. Noise levels were recorded at each station with a time interval of 5 minutes for about 30 minutes in each hour and were computed for equivalent noise levels for day-equivalent, night equivalent and day-night equivalent. Noise levels were monitored using sound level meter (CYGNET Model – 2013) for the study area. The details of sampling locations are presented in Table 4.7 along with data on the observed noise levels and noise equivalent levels. It is observed that noise equivalent levels of study area in the core zone varied in the range 50 - 53 dB (A) in the day time and 43 – 46 dB (A) in the night time. These observations indicate that the ambient noise levels within the core impact zone comply with prescribed standards for residential area. At the proposed project site, the values are also within the prescribed standards for residential and commercial area. Table 4.7 Equivalent Noise Levels in the Study Area (Core Zone) Station Code Locations L day dB (A) L night dB (A) L dn dB (A) N1 Project Site 50 45 47 N2 Near DDA Flats, Sector 16B, Pkt 3C, Phase II N3 Near DDA MIG, Sector 17, Plot A, Phase II N4 Near Metro View Apartments, SFS Flats, Sector 13, Pkt B, Phase II N5 Near DDA Park, Sector 13, Phase II 51 44 48 53 45 49 53 46 50 52 43 47 CPCB standards for Residential Area: 55 45 CPCB standards for Commercial Area: 65 55 CPCB standards for Sensitive Zone: 50 40 Note: 69
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proposed integrated complex for delhi judicial academy

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