Assessment of Noise Pollution of Kolkata Metro Railway System and Its Impact on Urban Receptors A Case Study

An assessment of noise quality was conducted at underground and overground metro stations, within the metro rakes (AC and Non-AC) and at an institutional building near elevated metro corridor to assess the exposure of Kolkata Metro Railway System. The present study was conducted in different hours (peak and non-peak hour) for different types of rake (AC and Non-AC) movement. Different noise descriptors including A-weighted equivalent noise (Leq), statistical noise (L10,L50,L90), noise climate (NC), traffic noise index (TNI), two hour noise dose (%ND) and corresponding time-weighted average (TWA) were calculated under the purview of the present study. Pearson’s correlation was performed between all noise descriptors to investigate the relation between them. Scatter plot analysis was conducted between L10 and %ND. In case of all study duration, all noise descriptors mostly exceeded FTA prescribed noise standard, along with 2-hr TWA which exceeded the OSHA guidelines of 100 dB for both AC and Non-AC rakes. On the other hand, at underground and overground metro stations, within metro rakes (except at day peak hour within AC coach) and at school building, mean value of traffic noise index (TNI) exceeded 74 dB (A), the threshold of over criterion. The study results indicate that Non-AC rakes are more annoying than AC-rakes. In all the study units, Leq was influenced by L10, which originates from pressure honking. There is very strong relationship observed between L10 and % ND. This study proposes that noise barrier should be installed at underground and overground metro stations, along the stretches of overground metro track, within metro rakes for developing the acoustic quality of Kolkata Metro Railway System and the areas of its immediate vicinity.