Noise level Status in various commercial zones of Birnendranagar municipality,surkhet,nepal

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1 Noise level Status in various commercial zones of Birnendranagar municipality,surkhet,nepal Dharma Raj Paudel Department of Physics, Midwestern University, School of Science and technology. Abstract: Noise is a type of pollution is an unwanted sound for human ear which causes various health related problems like sleep disorder, hearing loss, increase in blood pressure, annoyance etc. The noise survey was carried out at various places with relatively high traffic commercial area, using a decibel. The time of the survey was at the day time from 10 AM to 5 PM in the month of February It was found that all the places have noise level were all above the noise level standard purposed by WHO. The maximum was at Buspark, L eq 79.01dB(A) and minimum at Basnet Chowk, L eq db(a). The purpose of this study was to show noise levels at various places and to rise concerns over this pollution. Keywords: noise pollution, decibel, L eq, commercial zone, sleep disorder. INTRODUCTION Noise is an undesirable sound to human ear. When sound wave travels in a medium like air, solid or in liquid, then it may propagate as periodic, regular and long continued. In this case the sound produces a pleasing effect to the human ear. However, if propagation is such that it is non-periodic, irregular and of very short duration, it produces a displeasing effect. Such sound is called noise. The intensity of sound at a point is defined as the amount of sound energy crossing the point per unit area per second (P.K.Mittal, 2010). Because the ear is sensitive over a broad range of intensities, a logarithmic intensity scale is usually used. If I be the intensity of sound at a point under consideration, I 0 be the threshold of hearing also called reference intensity chosen to be watt/m 2, then sound intensity level β is defined by the equation

2 β = log ( I I 0 ) (D.Young, 2007). The unit of the intensity level is bel. The intensity level is said to be 1 bel when intensity(i) at a point is 10 times of the sound at threshold of hearing(i 0 ). Decibel is the smaller unit which is one-tenth of a bel. In terms of decibel, we have intensity level, β = 10 log ( I I 0 ) db. However, sound intensity level in decibel is rarely used for noise level measurement. Instead time-averaged value is used which is called the equivalent continuous sound level, symbol L eq. Some of the standards for noise level measurements are as follows (Thomas Munzel, 2014): (i) L eq : The energy-equivalent average A-weighted sound pressure level (LAeq) expressed in decibels is the most commonly used. It accounts for the different sensitivity of the human ear at different sound frequencies. The duration of the averaging period within the 24 h day is often amended (e.g., LAeq16 h, usually reflecting the period from 7 a.m. to 11 p.m.) (ii) L night : L eq for the night period (usually 11 p.m. and 7 a.m.) (iii) L DN : Weighted L eq over a 24 h period with a 10 db penalty for nocturnal noise exposure (usually 11 p.m. to 7 a.m.). (iv) L DEN : The 24 h L eq with a 5 db penalty for the evening (usually 6 p.m. to 10 p.m. or 7 p.m. to 11 p.m.) and a 10 db penalty for the night (usually 10 p.m. to 6 a.m. or 11 p.m. to 7 a.m.). The penalties are introduced to indicate people's extra sensitivity to noise during the evening and the night. With respect to long-term health effects, these are usually calculated as average annual exposure indicators. (v) L max : Maximum noise level in a given time period. L max is often better at predicting acute effects of single noise events than average noise levels. With respect to long-term health effects, however, equivalent sound levels seem more appropriate. Since there is no unique way of accessing sound and its effect, L eq is used most commonly in most of the countries. Pierre. B (2015) defines L eq steady sound pressure level which, over a given period of time, has the same total energy as the actual fluctuating noise. Mathematically it is given by L eq = 10log 10 ( 1 T L i dt), where T is the time period and L i is the noise level of i th sample. N For the discrete methodology, L eq = 10log 10 ( 1 f N i i L i), where N is the total number of data taken, and f i be the fraction of time that the sound level is in the i th interval which is taken as one second for slow response mode of sound level meter device (Bhattarai, 2014).

3 A decibel is a sound level meter in which sound level at a point can be measured by decibel expressed in a special setting called A setting. In this setting sound level meter responses in a similar manner as our ear responds. Most environmental sounds are made up of a complex mix of many different frequencies. Frequency refers to the number of vibrations per second of the air which the sound is propagating and it is measured in Hertz(Hz). The audible frequency rage in normally considered to be Hz for younger listeners with unimpaired hearing. However, our hearing systems are not equally sensitive to all sound frequencies, and to compensate for this various types of filters or frequency weighting have been used to determine the relative strengths of frequency components making up a particular environmental noise. The A -weighting is most commonly used and weights lower frequencies as less important than mid and higher frequencies. It is intended to approximate the frequency response of our hearing system. The effect of a combination of noise events is related to the combined sound energy of those events. The sum of the total energy over some time period gives a level equivalent level of the A-weighted sound over a period T. LA eq, should be used to measure continuing sounds, such as road traffic noise or types of more or less continuous industrial noises. Therefore L eq expressed in A-setting is simply denoted as L eq (dba). Effects of noise exposition to health According to WHO, safe noise level for the industrial or commercial shopping area is 70 db(a). The table (1) shows recommended values for different zones. In the table the safe zone for commercial zone is recommended as 70 db(a) for 24 hours. Similarly for outdoor living area it will be 55. When we are exposed outside environment greater than say these values, we will get different health related problems as indicated in the table. WHO (1999) has estimated that about 120 million Table1: Noise Level Standard for Different Zones (1999) Source: World Health Organization (1999) worldwide have disabling hearing difficulties.

4 WHO has also estimated that in western European countries, annually years are lost due to noise -induced cognitive impairment in children, due to noise induced sleep disturbance, due to noise -induced cardiovascular diseases, and due to tinnitus (ringing in the ear) (Thomas Munzel, 2014). In Nepal commercial area and high traffic area like highway are also the residential area for many people. Hence according to table 1, people are more vulnerable to not only sleeping disturbance, annoyance but also hearing impairment. Noise exposure modifies the function of multiple organs and systems. The continuous noise exposure can cause increase in blood pressure, heart rate and cardiac output (BabischW., 2011). As shown by the field studies, such effects occur not only at noisy occupational regions but also in the region having low sound level if concentration, relaxation or sleep is disturbed (Basner M, 2006). In UK, day-time noise level greater or equal to 55 db(a) have been estimated to cause an additional 542 cases of hypertension-related myocardial infarction, 788 cases of stroke and 1169 cases of dementia with a cost valued at around 1.09 billion annually (Harding AH, 2013). A significant higher systolic blood pressure per 10 db increase of the road traffic noise level was found in the middle-aged subjects participating in large Danish cohort study, with stronger and significant associations in men and older subjects (Sørensen M, 2011). Objectives To know the noise levels at different commercial zones in Birendranagar Municipility. To know the health related problems related to noise pollution. METHODOLOGY Study site Surkhet is the regional capital of Midwestern region and it is probable capital of the sixth state. It is located about 600 kilometers west of the national capital Kathmandu. Birendran is the district headquarter which is located in the Surkhet valley which serves as gateway of all Karnali regions as Karnali Highway starts from here. It has population 47,914 according to National population census It is also a centre of academic excellence in this region including Mid-western university at the heart of Birendranagar and also the center for commercial and tourism sector. Roads are often busy here due to high traffic. Six regions are chosen for survey: (i) Ghantaghar Chowk, Birendranagar -6 (ii) Mangalgadhi Chowk, Birendranagar -6, Jumla road (iii) Basnet Chowk Jumla road, Birendranagar -6,near Mangalgahi Chowk (iv)airee Chowk, Birendranagar -3, Jumla Road (v) Birendra Chowk, Birendranagar-6 (vi) Buspark, Birendranagar-6. Techniques of data collection

5 The intensity levels are measured by a decibel of version , android based A-weighting (ANSI S 1.4) device which is installed in a android smart phone. The decibel was set to slow response mode. Measurements were carried out at 10:00 AM to 5:00 PM in the month of February The sound intensity levels are measured at the 15 th second at the interval of 15 th second for 10 minutes which gives 40 reading at each sampling site at a time. Measurements were carried out at 10 am and 1 am and at 5 pm at each site. The data were taken at 15 m from the center of road side. There was normal atmospheric condition no high speed wind or rain falling during the time of measurements. RESULT AND DISCUSSION Noise level at a place depends on the nature of sound producing source, its distance. When we consider a road, then noise level is effected by density of flow of vehicles, their nature and conditions etc. For example, tractor produce more noise than an electric car. Road conditions also play vital roles; smooth road causes less sound emission than from graveled or unrepaired road. Pressure horns are also crucial for noise, for example, especially in bus park. Figure (1) below shows that noise levels in terms of L eq db(a) at different commercial regions of Birendranagar- municipality. The results shows that each place except Basnet Chowk, noise levels are above that recommended values prescribed by WHO. The maximum L eq of db(a) was observed at Buspark while minimum 67.3 db (A) was observed at Basnet Chowk. Figure 1: Noise levels expressed in L eq db(a) at different zones comparing with that of WHO recommended value. The values at the top of each represents L eq expressed in db(a).

6 The regions for high value of noise level is that they contain busy traffic all the day. The highest value at the bus park is due to the fact that it contains number of bus, including small vehicles like jeep, motorcycle with people s crowd. The running of traffic with pressure horns often raises the noise level to the maximum. The level of noise at Basneet Chowk is due to low traffic there and it is quite spacious regions with relatively less people s crowd. The Airee Chowk has also high value of noise due to the fact that it less spacious, contains high traffic and so much crowd of people. The building along the road sides are also the residential homes. Hence people in such houses are more vulnerable. CONCLUSIONS Carrying out noise intensity level survey at different places of Birendranagar municipality following conclusions have been derived: Bus park, which is located along side of Jumla Road is the noisiest place with sound intensity L eq of db(a). Basnet Chowk is the quietest place with L eq db(a). More than eighty percent sites (5 in 6) sites have intensity level above the recommended values 70 db(a) for commercial zones. But it is seemed that people make these sites as residential sites where recommended value is not more than 55 db(a). Hence there is greater probability that people may feel noise-induced health effects as discussed above. Further there are some hospitals along the road which are exposed continuously high noise intensity greater than 70 db(a), where recommended value is 30 db(a). This is a very serious problem. The main sources of noise pollution are the vehicles moving along the road, conditions of the road which are narrow and unrepaired. Sometime unnecessary pressure horns also contribute the rise of noise over there. Bad conditions of vehicles (e.g. using of old vehicles), high speed bikes along the roads also has contributed the rise of intensity levels. There is no specific bus station, bus or jeep can carry their passengers or goods from any place along the road. Hence this has increased the people crowd and noise intensity in the road. RECOMMENDATION

7 Here are some suggestions to reduce noise intensity levels in the places of study and in other places. The recommendations are as follow: Road should be repaired in the regular basis. Vehicles which are old, outdated should be banned from the city area. Vehicles should be checked and repaired in the regular manner. They should be provided with silencer of good condition. Government should make code of conduct regarding noise pollution. The code of conduct must have rules which avoid pressure horns in the city area, around the hospitals, along residential area. Further it should include about the speed limit of all vehicles and time duration to run the vehicles i.e. its life time. The code of conduct should strictly be implemented and if not checking should be made time to time. School areas, Hospital areas should not placed away from the highway. In such places horn should strictly prohibited. Residential sites should not be mixed with commercial zones. They should be placed far away from such high-traffic zones. If possible, sound proof walls can be built along side the road to control the noise inside such areas. Noise level map should be prepared for the town by the government. The noise levels at different places should be checked time to time. Awareness about the noise pollution, its effects on health should be carried out through different electronic media, print media, notice board or through different social campaigns. Syllabus of the schools or university should include the idea about this pollutions. ACKNOWLEDGEMENT The author is thankful for all the students of B.Sc., six semester of Midwestern university to assist in data collection at the study sites. REFRENCES BabischW. (2011). Cardiovascular effects of noise. Noise Health, 13: Basner M, S. A. (2006). Aircraft noise effects on sleep, application of the results of a large polysomnographic field study. J Acoust Soc Am,

8 Bhattarai, L. N. (2014). Noise Level Status in Siddharthanagar Municipality,Rupandehi, Nepal. Himalayn Physics. D.Young, H. (2007). University physics. Delhi: Dorling Kindersley (India). Harding AH, F. G. (2013). The cost of hypertensionrelated ill-health attributed to environmental noise. Noise Health, 15:8. P.K.Mittal. (2010). Oscillations,Waves and Acoustics. New Delhi: I.K. International Publishing House Pvt.Ltd. Pierre B., Denmark. (2015). Bru ël and KJaer application notes. Bru ël & kjaer. Sørensen M, H. M. (2011). Exposure to road traffic and railway noise and associations with blood pressure and self-reported hypertension:a cohort study. Environ Health, 10:92. Thomas Munzel, T. G. (2014). Cardiovascular effects of environmental. European Heart Journal. WHO. (1999). Guideline values of community noise in specific environments. London.