Sound can be described as the mechanical energy of a vibrating object transmitted by pressure waves through a liquid or gaseous medium (e.g., air) to a hearing organ, such as a human ear. Noise is defined as loud, unexpected, or annoying sound. In the science of acoustics, the fundamental model consists of a sound (or noise) source, a receiver, and the propagation path between the two. The loudness of the noise source and obstructions or atmospheric factors affecting the propagation path to the receiver determines the sound level and the characteristics of the noise perceived by the receiver. Frequency is expressed in terms of cycles per second, or Hertz (Hz). The audible frequency range for humans is generally between 20 Hz and 20,000 Hz.
Sound level is usually defined in terms of Sound Pressure Level (SPL). SPL is actually a ratio of the absolute Sound Pressure and a reference level. SPL is measured in decibels (dB), because of the incredibly broad range of intensities humans hear. Noise measurement readings can be adjusted to correspond to this peculiarity of human hearing and are generally called A-weighted decibels (dB)A. Equivalent Sound Level (Leq) represents an average of the sound energy occurring over a specified period. Maximum Sound Level (Lmax) is the highest instantaneous sound level measured during a specified period.
The various regulatory requirements of noise emissions play an important role in noise mapping and management studies. The regulations are defined for ambient environment and work zone environment. The noise levels in ambient air are primarily defied by Environmental Protection Act, 1986 whereas the noise levels in work zone are defined by the Factories Act, 1948 and Occupational Safety and Health Administration.
The noise mapping in the facility/ region will be done using scientific modelling tools based on noise generating equipment’s operated on continuous/ intermittent basis. Based on the prescribed regulatory norms, hotspots will be identified. Suitable mitigation and control methods will be suggested to comply the norms.