1.0 Introduction

Deepabali, the festival of light is a famous festival celebrated all over the country. This year it was celebrated on 1st November, 2005. But over the years Deepabali has also turned out to be a day of severe noise pollution due to bursting of fire crackers. Fire works & Fire crackers create a lot of pollution in terms of toxic fumes as well as noise generated. Over the years the general incidence of noise has been increasing. The rapid pace of development, volume of mobilization, construction of buildings, uncontrolled population growth including unabated migration of people, use of air horns in vehicles, music systems in the street shops and different social gatherings, all contribute to an increasingly noisy environment. This gets further exacerbated by the use of fire crackers during festival seasons.

2.0 Noise

Physically noise is a complex sound with little or no periodicity. Psychologically noise may be defined as the sound that is unpleasant and unwanted by the listener because of its bothersome nature, interference with the perception of wanted sound or its harmful physiological and psychological effects. Unpleasantness and harmful effects of noise depend upon factors like intensity of sound waves, frequency, duration of exposure and intermittence of sound.

3.0 Effects of Noise

Excessive noise can damage the ear. Depending upon the intensity and duration of noise, the person exposed to it, may suffer from temporary or permanent noise induced hearing loss. When a person is exposed to continuous even a short period of high intensity noise, the auditory sensitivity of the ear is reduced temporarily. In addition to hearing loss, excessive noise may also cause physiological and psychological disorders. These include nausea, dizziness, indigestion, metabolism, decreased heartbeats and variation in blood pressure, breathing difficulties and harmful effects on limb coordination and thinking ability. The mildest psychological effects of noise are physical & mental fatigue and lack of concentration. These in turn, lead to lowered efficiency, reduction of output, increased absenteeism and higher rates of accidents.

4.0  Ambient Noise Standards

Sl.
No / Area+ / Leq dB(A)
Day Time* / Night Time**
1. / Industrial Area / 75 / 70
2. / Commercial Area / 65 / 55
3. / Residential Area / 55 / 45
4. / Silence Zone*** / 50 / 40

* Day time - 06.00 am to 10.00 pm, ** Night time - 10.00 pm to 06.00 am

*** Areas up to 100 metres around certain premises like Hospitals, Educational Institutions, courts, religious places may be declared as Silence Zones by the Competent Authority. Honking of vehicle horns, use of loudspeakers, bursting of crackers and hawkers’ noise should be banned in these zones.

+ Mixed area should be declared as one of four aforesaid areas by the Competent Authority and the corresponding limit be applied.

5.0 Various Sound Levels and their Effects on Human beings

Sound sources / Sound Level in dB(A) / Subjective feeling of human beings / Effects on
Human being
Rockets and Missiles, Heavy explosives / 150 – 160 / Unbearable / Sound Intensity above 150 dB(A) may cause severe damage to the whole body such as loss of hearing of both ears, dizziness, nausea, disturbance of speech, confusion or psychosis
Jet planes, Cannons & Explosives / 140 / Unbearable
Aircraft propeller and Machine guns / 130 / Unbearable
Diesel, Steam engine & Crackers / 120 / Unbearable / Above 90 dB(A) headache, dizziness, tinnitus, insomnia, deafness, heart diseases, blood hypertension, gastric, ulcer, neurosis, temporary hearing threshold shift
Lorries, Highway vehicles and very busy streets / 90 – 100 / Very noisy / 50 – 90 dB(A) may cause various degrees of effects in sleeping, studying, working and talking
Commercial place, Air Conditioners, Loud voice & busy streets / 70 – 80 / Noisy
Office complex, Average loudness of voice / 60 / Noisy / Sense of noisy feeling
Ordinary room / 50 / Quiet / Pleasant feeling
Silent night, Library / 30 – 40 / Very quiet
Hospital, Bedroom
at Night, Church / 20 – 30 / Very quiet / Silence feeling
In sound proof room, Broadcasting Studio / 10 – 20 / Very quiet
Lower limit of hearing / 0 / Threshold of hearing

6.0 Objective of Noise Monitoring

In order to assess the noise level during Deepabali, noise monitoring was carried out in and around Agartala the state capital of Tripura, Udaipur in South Tripura, and Dharmanagar in North Tripura district during Deepabali festival on Normal Day (31.10.2005) and on Deepabali Day (01.11.2005). The main objectives of Noise Monitoring are:

To assess the ambient Noise Level status in and around Agartala, Udaipur, Dharmanagar on and before the Deepabali Night.

To compare measured Noise Levels against ambient Noise standards and to asses the extent of violation.

To identify the significant contributors of Noise Level so as to take overall decision for mitigation at the source itself.

To identify significant factors and its individual impact and to suggest alternative measures

To find collective significant factor and its collective impacts as to help to the planners to take decision at the earliest possible stage

To facilitate in evolving policy for laying down standards and to formulate legal action for punishment, prohibiting, and preventing noise

To communicate the information gathered to the public for awareness

7.0 Methods of Measurement

Sound Level Meters (SLM) SL-4001 were used for monitoring of noise levels. The noise levels were monitored at least for 30 minutes at each location during monitoring.

Leq Formula:

The ‘root mean square’ quantity of a sound wave is known as r.m.s excess pressure or more commonly as sound pressure.

Sound level is the sound pressure level in decibels (dB) and is 20 times the logarithm to the base ten of the ratio of a weighted sound pressure to the reference sound pressure. This is expressed as force per unit area either in Newtons per square metre (N/m2) or in Pascals (Pa).

“A- weighted” means making graded adjustments in the intensities of the sound of various frequencies for the purpose of noise measurement so that the sound pressure level measured by an instrument reflects the actual response of the human ear to the sound measured.

Steady Sound pressure Level which over the given period of time would have given the same total energy as the actual fluctuating time. Thus Leq is the r.m.s sound pressure level taking the measurement duration as the averaging time. It is calculated as follows:

n

Leq. = 10 log( å fi 10 Li/10 )

i=1

Fi = Fraction of time for which the consent SPL persists

Li = Sound Intensity Level

Lmin = Minimum Noise Level during the period of measurement

Lmax = Maximum Noise Level during the period of measurement

e.g. Noise level measured after every 10 minutes are 65dB, 70dB, 80 dB, 60dB, 75dB. Calculate the Leq.

Here Lmin = 60 dB, Lmax = 75 dB

Leq = 10 log 1/5(1065/10 + 10 70/10 + 10 80/10 + 10 60/10+10 75/10)

=74.65`

=> 75 dB

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Tripura State Pollution Control Board