Acoustic Assessment of a Precast Factory in Kolkata, India

Sustainable development has various indicators like transport system, economy, land use etc. Quality of life is one of them and protection from noise, especially at workplace plays a prime role in determining it.Numerous literature surveys have revealed that the construction industry ranks second in terms of thestaff being exposed to loud noise and its consequent hazards. A similar situation was observed in a major infrastructure project in Kolkata, India. A questionnaire survey among the workers and a 3D simulation model was created to assess the noise levels. The results revealed that the perceived noise levels were significantly high and exceeded the limits set by concerned authorities. This warranted actions to reduce noise levels. To achieve this, two alternate simulation models were created with altered acoustic properties. The results of these simulations reduced noise to identical levels, which were lower than the limit set. And hence, it was concluded that lower noise levels could not be achieved and was proposed that adopting either of the two would fit the purpose.


Introduction
Sustainable development may be defined as one in which the inhabitants enjoy good quality of life and which makes sure not to transfer environmental or health and socio-economic problems to other placed or future generations (Coelho & Alarcao, 2006). It aims at delivering basic social, economic and environmental services to the inhabitants without endangering the viability of natural, built and social systems upon which the delivery of these services rely upon. Therefore, sustainable development requires a careful balance between sustainable economy, proper housing and health of inhabitants, clean environment, sustainable transport system and efficient land use.
Noise, however disrupts this balance by affecting almost all the elements. Harmful noise, with its negative health impact, is the second largest environmental polluter worldwide (WHO, 2001). And, the overall loudness of environmental noise is on an exponential rise over the years (Chedd, 1981). The World Health Organization (WHO) estimates that the Disability Adjusted Life Years (DALY) lost due to environmental noise are "6000 years for ischemic heart disease, 45,000 years for cognitive impairment of children, 903,000 years for sleep disturbance, 21,000 years for tinnitus and 587,000 years for annoyance" (WHO, 2001). And, Noise Induced Hearing Loss and Noise Induced Tinnitus are significant public health issues (Nelson, Nelson, Concha-Barrientos, & Fingerhut, 2005). Considering the importance of all these issues, noise protection is an important indicator of sustainable development.
As per the National Institute of Safety and Health (NIOSH), in 2007, nearly 23,000 cases of occupational hearing losses were reported and this accounted for 14% of all cases of occupational illness in 2007. A study revealed that between 1996 and 2010, around 58% of the workers experienced abnormal hearing loss owing to noise, and the construction industry saw the second highest number of workers exposed to noise hazards. And the fact that hearing losses are irreversible aggravates the situation.
The practice of recording the exposure to high levels of noise in construction is not new (LaBenz, Cohen, & Pearson, 1967;), yet it continues to remain a major hazard to the staff. Recent estimates suggest that more than half a million construction staff is exposed to harmful noise (Suter, 2002;Lusk, Hong, Ronis, Eakin, Kerr, & Early, 1999

Questi
The questi working in from these follows:  Vol. 7, No. 4; Therefore, majority of the participants (89%) were under the age of 40. And hence, the chances of the responses to the questions being age driven were low. The mean and standard deviations for the other responses were as follows: These figures clearly reflect that the prevailing acoustics in the factory were very poor, leading to increased Working Level Noise (Gerhart Tieslera, Rainer Machnerb, Holger Brokmannb 2015) and distress among the workers. Some of the responses like those for Difficulty in Hearing, Communication, Annoyance and Sleep Disorder were quite alarming and prompted for an immediate assessment of noise level and its subsequent reduction.

Sound Spectrum of Sound Sources
Sound Spectrum was required for defining the acoustic properties of the noise sources, which would be inputs for calculation of the Noise Levels in i-Simpa. The sound spectrum of the sound sources was measured by a Sound Level Meter. The readings were taken by holding the instrument close to the sound sources. Five sets of measurements were taken. The average of the readings obtained was:

Base
The base m unaltered.
The result level decre long or rep exposure t situation w