Performance Analysis of Road Traffic Noise by Using Computer Aided Modelling

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Volume 2, Special Issue 1 MEPCON 2015

158 Available online at www.ijiere.com

International Journal of Innovative and Emerging

Research in Engineering

e-ISSN: 2394 - 3343 p-ISSN: 2394 - 5494

Performance Analysis of Road Traffic Noise by Using

Computer Aided Modelling

Vaibhav kishorrao Pete1

a

_{and Prof. M.P.Nawathe2}

b

a_{ME-Mechanical (CAD/CAM) Scholar, PRMIT&R, Badnera, Amravati, Maharashtra, India} b_{Associate professor, PRMIT&R, Badnera, Amravati, Maharashtra, India}

ABSTRACT:

In rapidly urbanizing country like India, the transportation sector is growing in a fast pace and the number of vehicles on Indian roads is increasing at a rate of more than 7% per annum. This has led to overcrowded roads and pollution. Transportation sector is one of the major contributors to noise in urban area, which contributes 55% of total noise on highway. In view of this, it is essential to study highway noise with respect to various causative factors. Hence, various noise prediction models have been developed, throughout the world to assess its impact on to the society and the human beings. These traffic noise prediction models differ in some respects, but the overall methodology is similar. All the noise prediction models consists of evaluating basic noise levels and making series of adjustments to take into account geometric, traffic flow, barrier data etc.

Keywords: FHWA model, CORTON model.

I. INTRODUCTION

Noise is one of the environmental pollutants that is encountered in daily life. The exposure to noise from highway, affects more people than noise from any other source [1]. It is not at all surprising that the adverse impact from highway noise is one of the major concern to planners, regulatory agencies, and effected individuals and communities. Several state agencies have implemented regulations that specify procedures to conduct noise studies. These regulations led to the advancement of computerized method for predicting highway noise [2]. Surface transport noise is not a new problem. “In the twentieth century, New York was reported to be the noisiest city of the world probably because of its elevated railways”. In 1929, a noise abatement commission was appointed to study the noise pollution in New York City. In Great Britain, a committee on noise for the operation of mechanically propelled vehicles was appointed in 1934 and recommended legislation to sound level limits for vehicles [3]. The well known Wilson committee report on noise drew attention to the serious problem of road traffic in Britain in 1936. In US quantitative limits for vehicle noise were first introduced by individual states beginning in the year 1965 with New York.

Which sets a limit of 88 dBA measured at 15.56 m from the central of traffic lane. The study carried out by an Organisation For Economic Co-operation & Development (OECD) group of experts review the current state of the art and national experience with noise abatement techniques for new and existing roads [4].

II. LITERATURE REVIEW

Reddy studied traffic related environmental factors such as noise and air pollution at some selected locations in Delhi metropolitan city. At about 12 busy intersections on NH -2 , the noise level and the traffic volume was recorded.

Result shows that even minimum noise level limit was higher than the maximum recommended limit of 65 dBA. Rao studied two different locations at Vindhyachal project for estimating the vehicular noise pollution. Prediction

of the ambient noise level Leq the equivalent continuous noise level at a particular place can be expressed in the form of an equation. Leq= C + Klog10 Nx

Where C and K are the constant; and Nx, equivalent number of vehicles per hour of a particular category corresponding to the total mixed traffic density.

The ambient noise level Leq value for individual hour has been calculated using the equation: Leq = 40.60 + 9.5log10 Nl, Leq = 40.50 + 15.4log10 Nh

Where Nl and Nh are respectively the equivalent number of light vehicles and equivalent numbers of heavy vehicles per hour obtained after conversion.

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159 P Kumar carried out individual vehicle noise level study for proper categorization of vehicles and developed basic noise level equations for each type. He further calibrated noise prediction model for traffic noise prediction for Indian conditions.

III.TRAFFICNOISEANALYSISPROCESS

The major objectives of a noise study for new highway construction or a highway improvement are:  To define areas of potential noise impact for each study alternative

 To evaluate measures to mitigate these impacts

 To compare the various study alternatives on the basis of potential noise impact and the associated mitigation costs

Traffic noise studies thus provide useful information, directed primarily to two distinctly different audiences – 1) The government decision maker and 2) The lay public. For the government decision maker, the study should provide a portion of the data needed for the informed selection of a satisfactory project alternative and appropriate mitigation measures. For the lay public, the study should provide discussion of potential impacts in any areas of concern to the public. The final product of a highway traffic noise study should be a clear. There should be a stand-alone discussion, a noise study report that gives the reader a detailed description of all the elements of the analysis done for the study, including information on noise fundamentals and regulatory requirements. The key elements of a highway traffic noise study are as follows:

 Definition of impact criteria and identification of noise-sensitive land uses  Determination of existing noise levels

 Prediction of future traffic noise levels for study alternatives  Identification of traffic noise impacts for study alternatives  Identification and consideration of abatement

 Consideration of construction noise

 Coordination with local government officials

IV.METHODOLOGY

 Methods (Instruction) used to achieve the object i.e. to measure the sound level.  The “Sound level meter” which measures the intensity of sound in dB (A)

 Instrument: In this project “8928 Digital Sound Meter” is used to measure the sound level specifications are as follows.

 Model: 8928 digital Sound level Meter.  Measurement frequency rating: 300Hz-8 kHz.

 Quasi: Analog Bar indicator: 1dB display steps, 30dB display range updated every 50m.  Measurement (level ranges): 4ranges: 40-70dB, 60-90dB, 80-110dB, 100-130dB  Measurement level A weighting: 40dB - 130dB.

 Measurement level C weighting: 45dB – 130dB. Accuracy: ± 2 dB  Microphone: 10mm (Diameter) Electric condenser microphone.

 Digital display: 3 ½ digital LCD, 0.1dB resolution updated every 0.5 second.  Power: 9 V battery (included)

Weighting:

Sound is defined as any pressure variation that the ear can detects ranging from the weakest sounds to sound levels which can damage the hearing. The human ear response is not linear in the entire audible frequency range of 20 Hz to 20 kHz. Hence, weighting of noise spectrum is done in a way which corresponds to the response of the human ear. Since weighting do not give good correlation to subjective tests, a weighting has found almost complete acceptance for measurement of all sound levels. The basic main parts contents in any noise meter are as follows

1) Microphone 2) Amplifier 3) Rectifier 4) Smoothing Circuit 5) Meter 6) Operation

1. Microphone: A high quality microphone converts air pressure variation of the sound into electrical signal with voltage proportional to sound pressure variation.

2. Amplifier: Amplifier mounted closed to microphone converts high input impedance into low impedance. 3. Rectifier: After amplification and appropriate weighting the signal applied to special rectifier. This include well

defined time constant for averaging the A.C. level fluctuation of signals, producing a D.C. proportional to root mean square level.

4. Smoothing Circuit: Smoothing circuit is a electrical board.

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160 Decibel meter

6. Operations : Various operations of the sound level meter are as follows:

a) The ON/OFF: Key is used to turn meter on/off. The meter will begin measuring the current sound measure level b) Selecting the response time: To select the respond mode (fast or slow) time to different applications and standard,

this key is used. Most OSHA related testing is done using slow response time and a weighting.

c) Weighting A/C: A weighting enables the meter to respond in the same manner as the human ear which increases and decreases amplitude over the frequency spectrum.

d) Freezing the maximum Sound Level Recording: Maximum hold key is used to frequency the maximum reading. The digital display will remain unchanged until a higher reading is detected.

e) Recording Maximum and Minimum Measurements: This is used for recording the maximum and minimum measurements.

f) Limitations:

1. The noise level can be measured from the frequency range 300Hz to 8 kHz only. 2. The measuring level of a weighting of this noise meter is 40 dB – 130 dB only. 3. Measuring level C weighting is 45 dB to 130 dB only.

4. It can give accuracy up to ± 2 dB .i.e. there is ± 2 dB variations in the reading

V. SITESELECTIONCRITERIA

Several scouting trips were conducted to identify appropriate sites for the noise measurements. At first it was hoped that aerial photographs and GIS records could be used to identify sites, but when the first sites were investigated in person, it was found that they had undesirable characteristics which could not be filtered through either of these methods. Thus, several trips were required to identify enough sites that would meet the criteria and be appropriate for the measurement methods. The final criteria included:

 The dominant species must be coniferous (the dominant species is defined as the species that dominates the forest canopy)

 The site must be at least 20 m (65.6 ft) deep (tree depth) • The site must be level in grade and even with the road

 The site must be accessible for measurements (researchers able to enter woods to take measurements; no posted private land; stay within VDOT right-of-way to the degree possible)

 The site must be safe for the roadside researcher to take noise measurements and traffic counts  There must be a safe place to park the research vehicle

 If there are deciduous trees at the site, they must not yet be leafed out.

VI.MODELS

A.TRAFFIC NOISE MODEL (TNM)

Prior to the release of the TNM, the Highway Traffic Noise Prediction Model, or "108 model," was in use for over 20 years. Although an effective model for its time, the "108 model" was comprised of acoustic algorithms, computer architecture, and source code that dated to the 1970s. Since that time, significant advancements have been made in the methodology and technology for noise prediction, barrier analysis and design, and computer software design and coding. A state-sponsored, pooled-fund effort supported the development of the national reference energy mean emission levels (REMEL) database for the TNM. The TNM is an entirely new, state-of-the-art computer program used for predicting noise impacts in the vicinity of highways. It uses advances in personal computer hardware and software to improve upon the accuracy and ease of modelling highway noise, including the design of effective, cost-efficient highway noise barriers. The TNM contains the following components:

 Modelling of five standard vehicle types, including automobiles, medium trucks, heavy trucks, buses, and motorcycles, as well as user-defined vehicles.

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161  Modelling of the effects of different pavement types, as well as the effects of graded roadways.

 Graphically-interactive noise barrier design and optimization.  Attenuation over/through rows of buildings and dense vegetation.  Multiple diffraction analysis.

 Parallel barrier analysis.

B. FHWA MODEL

In response to widely recognized short coming of National cooperative Highway Research Program (NCHRP), Tuberous sclerosis complex (TSC) models, the FHWA (federal highway administration) developed an in house model [15]. The FHWA Model calculates noise level through a series of adjustment through a reference sound level. The reference sound level is the energy mean emission level, which is determined through field measurements of individual vehicle pass by for each vehicle type (cars, medium trucks, heavy trucks). Adjustments are then made to this level to account for traffic movement, varying distance of receivers from the roadways, finite length roadways and for shielding effects. The basic emission and propagation equation for the FHWA model is mathematically stated as

Leq(b)i=(Lo)Ei+10 Log [(Vi O Do) / (Si T)] +10 log [Do/D]+PG +PB

C. CORTN MODEL

It was developed in the UK in 1988 by the department of the environment and Welsh office[16]. First of all the basic noise level at a reference distance of 10m away from the nearside carriageway edges is obtained from the traffic flow, the speed of the traffic , the composition of the traffic , the gradient of the road and the road surface. This model determines both the L10(18 hour) (0600-2400) and L10(1 hour) noise levels and takes into account traffic parameters such as volume, percentage of heavy vehicles speed, road surface and grade . Sound propagation factors include the distance of the noise surface, ground type, height of the noise surface shielding provided by barriers and reflections from facades .As with all such model, sites with particularly complex topography or traffic conditions require the traffic route to be split into segments in which each parameter is constant. Predictions are then made for each segment in turn and the total noise level combined logarithmically. Vehicles are considered as being either passenger vehicles or heavy vehicles (unlade weight exceeding 1525 kg). A mean speed of all vehicles is used in calculation L10 noise level at a receiver point is calculated as follows.

L10=Lo + P f + Pg + P p+ Pd + P s+ P a+ Pr

Where Lo is base noise level measured at 10m from the edge of the pavement; Pf traffic flow adjustment; P g gradient adjustment; P d , distance adjustment; Ps, shielding adjustment P r, adjustment for reflection; P p, pavement type adjustment; and Pa ,angle of view adjustment.

The base noise level Lo is calculated at a distance of 10m from the near side edge of closest traffic as follows. L10 (18 h) = 29.1 +10 log QdBA

L10 (1 h) = 42.2 +10 log q dBA

Where Q, total vehicle flow in the time period 0600 h to 2400 h and q, total vehicle flow within the hour considered.

D. THE STOP-AND-GO MODEL

This model was developed for central part of Bangkok by Urban Transport Department in 1997 by Pamanikabud and Tharasawatpipat [17]. The research focuses toward formulating an empirical model of interrupted traffic flow in Bangkok using two analytical approaches. The first being the single model analysis, and the second, the separated model or dual model analysis. In this study, several parameters that are considered to have possible influences on the interrupted traffic flow noises were measured at the study sites. Then, these were tested for their correlation with traffic noise levels. The parameters consisted of vehicle volume which is classified into different vehicle types appearing on the Bangkok roadways, average spot speed of vehicles in the traffic stream, road width, distance from curb to building façade, and distance to the nearest intersections. In the analysis of data, these parameters also were separated into nearside and far side roadway parameters. In this study, the distances to building facade were applied by two parameters. The first was the distance from observer to nearside building facade, and second, the distance from observer to far side building facade. Geometric mean of the roadway cross-section was introduced as one of the parameters in the analysis of the stop-and-go traffic noise model. Tests were conducted to determine the correlation of various parameters with the traffic noise level in Leq as well as the co-linearity among these parameters if they existed. The sets of parameters which correlated highly with Leq were used further as input in multiple regression analysis. Stepwise analysis technique was adopted in the multiple regression analysis processes of the study. Individual noise characteristics at an overall mean vehicle speed was used to identify the proportional weighting scale of the noise levels generated per unit of each vehicle type in relation to an automobile unit. The overall spot speed range obtained from the field survey data of this research together with the value for overall mean vehicle speed (of 33 km/h) were superimposed onto the vehicle noise characteristics. As there are many vehicle types that are in use in Bangkok, these were classified into seven groups based on the similarities in their noise level characteristics within the speed range that was observed in this study. From this analysis, the proportional weighting scale of the noise levels generated by each vehicle class was calculated. With this information, the traffic of traffic used in the model then could be described in terms of the noise generating ratio of each vehicle type in comparison with automobiles in Bangkok’s urban traffic.

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162 Volume of traffic (VnorVf)=AU+1.04(LT+1.12(MT+TT)+1.14(HT)+ 1.09(MC+BU+MB)

Where AU stands for automobile; HT, heavy truck; LT, light truck; MC, motorcycles; MT, medium truck; BU, bus, and TT for tuk-tuk. In order to validate the model, another set of data was collected from 10 new locations in the central part of Bangkok. The results indicated that the mean differences between measured and predicted values of 0.09192 dB (A) and 0.02219 dB (A) occur in the goodness-of-fi t test with 127 data sets for acceleration and deceleration lanes, respectively.

E. THE ASJ MODEL

In 1975, the Acoustical Society of Japan published a method of predicting a pseudo-L50 resulting from freely flowing road traffic. It was reported by Koyasu in 1978 and up-dated by Takagi & Yamamoto in 1993 . The up-dated version contains a direct method of calculating Leq. This is termed as A-method. The ASJ model also includes an empirical method called the B-method which is valid only far from the line source.

The sound power levels for traffic stream can be calculated by: For two classes of vehicle:

LW = 65.1 + 20 log V + 10 log (a1 + 4.4 a2),

Where a1 and a2 are the proportions of light and heavy vehicles. For three classes of vehicles:

LW = 64.7 + 20 log V + 10 log (b1 + 1.5 b2 + b3),

Where b1, b2, and b3 are constants corresponding to light, medium, and heavy vehicles. The ASJ method admits of a precise, A-method and an empirical B-method.

A-method:

is method calculates the octave band spectra. These are derived from the band centre frequencies from 63 to 4,000 Hz according to the equation:

L(f) = –10 log {1 + (f/2,000)} ± 2.5 log (f/1,000). B-method

Δt = Δd/v,

Where Δd is the spacing between the vehicles.

The basic propagation equation is based on Rayleigh [22], but modified to incorporate the A-weighting.

Leq =10 Log [∑10Lwi/10 øi2 / 2π

VII. OBSERVATION

In the present study, a noise sample size of 5 min in each hour at a particular selected distance from the edge of the pavement was taken. Noise sample were collected in db (A) scale at every 60 sec interval or total 5 reading in 1 sample size. Also, the traffic volume survey was also carried out during the observation. The number of vehicle passing through the observation station where counted for 5 min duration in an hour. The vehicles were divided into the sub categories such as 2 wheelers, 3 wheelers, 4 wheelers (light& heavy). The observation reading are taken at a distance 2.2 m from the edge of road at right angle to the centerline of road.

Date : 1/12/2014 location: In front of Hotel Gauri Inn, Amravati Sr. no. Time Time interval in second Noise levels in db (A) Traffic survey

2w 3w 4w light heavy

1 8am-9am 0-60 72.8 20 3 4 10

60-120 67.4

120-180 70.9

180-240 78.4

240-300 70.8

2 9am-10am 0-60 79.2 18 7 8 22

60-120 80.5

120-180 81.7

180-240 77.7

240-300 79.4

3 10am-11am 0-60 81.6 25 6 12 28

60-120 74.9

120-180 72.9

180-240 70.3

240-300 76.2

4 11am-12pm 0-60 79.7 30 8 20 26

60-120 69.8

120-180 80.3

180-240 74.8

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163

5 12pm-1pm 0-60 65.4 20 9 16 22

60-120 65.8

120-180 83.7

180-240 74.6

240-300 67.5

6 1pm-2pm 0-60 76.1 25 10 12 28

60-120 72.4

120-180 79.8

180-240 84.7

240-300 74.5

7 2pm-3pm 0-60 83.9 22 6 14 25

60-120 80.7

120-180 71.4

180-240 72.4

240-300 70.1

8 3pm-4pm 0-60 70.7 20 5 11 29

60-120 70.5

120-180 77.8

180-240 73.8

240-300 69.4

9 4pm-5pm 0-60 82.9 23 8 16 32

60-120 87.5

120-180 76.1

180-240 71.8

240-300 76.4

10 5pm-6pm 0-60 79.1 21 5 15 31

60-120 71.6

120-180 74.9

180-240 81.6

240-300 80.4

11 6pm-7pm 0-60 80.3 25 6 13 30

60-120 80.5

120-180 80.3

180-240 80.2

240-300 78.5

12 7pm-8pm 0-60 83.2 20 3 4 22

60-120 84.2

120-180 83.7

180-240 81.7

240-300 78.6

Date: 15/12/2014 location: At MIDC Crossing Sr. no. time Time interval in second Noise levels in db (A) Traffic survey

2w 3w 4w light heavy

1 8am-9am 0-60 80.6 7 1 10 13

60-120 84.7

120-180 68.3

180-240 74.60

240-300 71.3

2 9am-10am 0-60 76.1 8 0 9 24

60-120 72.4

120-180 70.3

180-240 75.2

240-300 79.4

3 10am-11am 0-60 67.5 15 1 14 32

60-120 76.8

120-180 73.9

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164

240-300 66.5

4 11am-12pm 0-60 70.2 22 2 24 27

60-120 90.2

120-180 72.3

180-240 73.5

240-300 66.2

5 12pm-1pm 0-60 80.1 5 0 14 20

60-120 83.4

120-180 81.7

180-240 71.3

240-300 76.6

6 1pm-2pm 0-60 71.5 7 0 10 26

60-120 73.0

120-180 69.6

180-240 67.3

240-300 77.8

7 2pm-3pm 0-60 68.5 6 0 12 24

60-120 70.4

120-180 77.3

180-240 76.4

240-300 80.1

8 3pm-4pm 0-60 67.5 8 0 12 27

60-120 80.1

120-180 83.4

180-240 77.4

240-300 84.6

9 4pm-5pm 0-60 79.8 6 0 14 29

60-120 80.7

120-180 76.8

180-240 79.4

240-300 80.7

10 5pm-6pm 0-60 86.4 22 2 21 27

60-120 87.1

120-180 80.4

180-240 84.7

240-300 82.1

11 6pm-7pm 0-60 77.6 16 0 14 25

60-120 79.3

120-180 79.4

180-240 76.9

240-300 78.4

12 7pm-8pm 0-60 79.8 6 0 15 23

60-120 80.9

120-180 82.4

180-240 83.7

240-300 82.6

VIII. SUMMARY

The purpose of traffic study is to monitor and assess the traffic generated noise in its spatial temporal aspects on highways which matches with the regional and climatologically conditions of the particular area on the basis of several parameters such as:

 Traffic flow/ volume of traffic  Percentage of commercial vehicles  Types of vehicles

 Speed of the traffic

 Road surface/pavement characteristics

 Physical characteristics of the road such as curves, hills, depression, elevation and grade.  Measuring distance from the roadway.

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165  Height of the building around the road

 Geometric parameters.

IX.CONCLUSION

Based on the critical review of the models, it can be concluded that within the range of validity, the models reviewed here meet the requirements of government regulations and many designers. Some models allow for other road vehicles as well as automobiles and trucks, and one includes car parks.

All the models discussed here have acoustic energy descriptions usually explicit as Leq or in two cases as a pseudo-L10. The Leq models admit of easy corrections for interrupted flow, multiple streams, and multiple roads. The eight models reviewed here are designed to meet the requirements of roadway engineers. However, they do not meet the requirements of other users of traffic noise models. The ideal model is proposed to supply all the deficiency. Therefore, there is a need to develop an ideal model which satisfies all the constraints.

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