RESEARCH ON MOTOR TRANSPORT PRODUCED NOISE ON GRAVEL AND ASPHALT ROADS

. Vehicles in motion on roads are the main source of noise in the environment. Th e noise in a car is created by structural noises from car construction, originated from vibrations in an engine, cabin, silencer, wheels and tires. Traffi c noise fl ow depends on its intensity, motion speed, fl ow composition and extent, quality of the road pavement and build-up of the area along the road. Th is paper contains research on motor transport produced noise levels on roads of regional signifi cance with gravel and asphalt pavement in Molėtai district. Th e level of motor transport produced noise was measured in wintertime and summertime at the chosen typical locations considering the nature of the asphalt and gravel road pavement and diff erent landscape morphology forests, topography roughness, open area, upslope, downslope, etc. Also, research of noise level dependence on car speed was performed from 50 km/h to 70 km/h. It was determined during the study that noise level produced by a car moving at a speed of 50 km/h on a road with gravel pavement is higher by 4 dBA than that on a road with asphalt pavement. Upon moving away from the noise source by 50 m, the level of noise decreases by 12 dBA in woodland open areas and by 16 dBA. As car speed increases from 40 km/h to 50 km/h in wintertime, the level of noise rises by 2 dBA. In summertime, as car speed increases from 50 km/h to 70 km/h, the noise level rises by 5 dBA. Th ese diff erences are due to the presence of ice and snow on the road in winter. Noise depends on physical properties of tires, type of pavement, car vibrations and in particular on pavement roughness.


Introduction
As industry develops, cities grow and the number of vehicles increases, zones of acoustic discomfort also expand increasingly. Skrodenis et al. (2009) note in their paper that people are constantly aff ected by noise produced by machines, equipment and devices. Motor transport is the main source of noise in cities and villages. Th e noise carried from streets, roads and highways forms a part of 80% of athmospheric pollution (Grubliauskas, Butkus 2009). Th e acoustic pollution produced by all types of vehicles occurs as noise and vibration (Topila et al. 2000).
Nowadays, noise has become a common problem, covering all areas of people's life and work. Th e harm of noise must be evaluated in pathophysiological, economical and sociological aspects and in accordance with the latest scientifi c achievements (Bazaras et al. 2008;Paslawski 2009;Willich et al. 2006).
Various studies confi rmed the infl uence of noise on cardiac infarct risk at places such as work and residence (Zavadskas et al. 2007a;b).
Research works carried out in Europe showed that almost 25% of population is annoyed by noise produced by vehicles. Th e noisiest vehicles are trucks, buses, sports cars and motorbikes (Oškinis et al. 2004). During the research performed in the USA, it was determined that the noise level produced by heavy vehicles moving at a speed of 100 km per hour had reached a value of 87 dBA, medium vehicles -83 dBA and light vehicles -77 dBA.
On 25 June 2002, the European Parliament and the Council adopted Directive 2002/49/EC On Assessment and Management of Environmental Noise. Th is is the fi rst document in Europe which seeks to legally regulate environmental noise (Nemaniūtė 2007).
Vehicle produced noise on roads is mostly infl uenced by the following factors: vehicle traffi c intensity and driving speed, its change and reduction of friction between wheels and road (Baltrėnas et al. 2007;Butkus et al. 2008;Vaiškūnaitė et al. 2009).
Th e main cause of the increased noise in streets is a high number of old and technically badly-maintained cars. During the last ten years the transport fl ow in Lithuania has increased 2.4 times. Because of this, a number of traffi c accidents have also increased. Th e drivers experience longer queues and time losses at junctions (Antov et al. 2009). As a result, environment pollution with exhaust fumes, and traffi c noise has increased considerably (Jonasson 2007;Kapski et al. 2008).
A major part of Lithuania's network of regional and local roads is comprised of roads with gravel and roads with worn-out AP. Technical condition of roads is the worst where the intensity of traffi c is growing constantly and the road pavement is not protecting the road structure from the traffi c loads and impact of weather conditions. Cars driving on roads of bad condition raise dust and produce noise and this negatively impacts the business and residential zones in regions (Gražulevičienė et al. 2004). Rutted asphalt roads not only worsen driving quality and increase dustiness but also create additional noise. To reduce rut formation Radziszewski (2007) in his paper recommends using asphalt mixture and binder modifi cation eff ective for improving asphalt properties. Laurinavičius and Oginskas (2006) in their work indicate causes of rut formation and presents recommendations on fi ghting it.
Noise has a negative impact on our body although we do not feel it. Th e reaction of each individual to noise is diff erent, however the body is under constant stress (Levine et al. 1998;Malinauskienė et al. 2004;Passchier, V. W., Passchier, W. F. 2000).
With the purpose of reducing this impact the Gravel Road Paving Programme has been implemented in Lithuania since 2004. First of all the roads passing through villages are paved, then the roads with higher traffi c intensity and gravel roads connecting larger villages with the network of asphalt roads. Building of bypasses and paving of gravel roads are highly signifi cant measures for air quality improvement. To reduce motor transport risks to human health it is planned not to exceed the noise level of 65 decibels on the newly built and reconstructed roads in living environments, to reduce the number of traffi c accidents and to inform the public of potential health impact (Miškinis 2006).
An alternative to road noise reduction without road paving is the erection of noise absorbing or refl ecting walls along the roads (Grubliauskas, Butkus 2009;Ishizuka, Fujiwara 2004;Vaišis, Januševičius 2008).
Th e objective of the research is to make an analysis and to compare the levels of motor transport produced noise on the roads of regional signifi cance with asphalt and gravel pavement in Molėtai district. Th e measurements were taken in wintertime and summertime, when there is diff erence in traffi c intensity and also in driving and climate conditions.

Noise measurement technique
Th e nature of noise is determined prior to the measurement. Motor transport noise is variable dependent on time of the day. Noise produced by motor transport fl ow is constituted of the noise produced by single cars. Variable noise is noise with variation higher than 5 dBA and constantly changing, intermitting or pulsating and it is assessed by the reciprocal and max sound levels as it is indicated in the document LST ISO 1996ISO -1:2005 Akustika. Aplinkos triukšmo aprašymas, matavimas ir įvertinimas. 1 dalis. Pagrindiniai dydžiai ir įvertinimo tvarka (Acoustics. Description, Measurement and Assessment of Environmental Noise. Part 1: Basic Quantities and Assessment Procedures (idt ISO 1996(idt ISO -1:2003).
Th e Bruel and Kjaer 2260 noise and vibration meter was used to measure the reciprocal and max sound levels. Th e relative error of this meter is 1.5. Th e Bruel and Kjaer 2260 meter is a state-of-the-art fi rst class sound level meter and sound analyser. Th is mobile device is suitable for the required measurements and full analysis of measured data when performing the research of noise in living environments and workplaces.
During the measurement the microphone of the noise meter is held at a height of 1.2-1.5 m and not less than 0.5 m away from the person who is performing the measurement and is also pointed to the noise source.
Measuring conditions shall conform to certain requirements: measurement shall not be performed when it is snowing or raining or wind speed is exceeding 5 m/s. In the event that the wind speed is 5 m/s or more, the microphone shall be covered with a special screen. Also other meteorological conditions shall be recorded: wind direction, air temperature, pressure and humidity. All measuring conditions met the current equirements.
Th e measurement of vehicle produced noise at the chosen location was performed (by LST ISO 1996 -2 standart) with two microphones at the same time: at point A (at a distance of 7.5 m from the axial line  of the trajectory of a moving car) and point B (at a distance of 20 m); at point A (at a distance of 7.5 m from the axial line  of the trajectory of a moving car) and point C (at a distance of 50 m) (Fig. 1). Th e measurements of car produced noise levels were performed on roads of regional signifi cance of Molėtai Fig. 1. Points selected to measure noise level produced by a moving vehicle district. Th e Molėtai district was chosen due to the fact that it has both asphalt and gravel road pavement.
Typical points in consideration of pavement nature and diff erent environmental conditions were selected (Fig. 2).
Th e fi rst measurement point was an asphalt road with an arable fi eld on one side and a meadow with thinly growing bushes on the other; an open location was selected for the measurement.
Th e second measurement point was a gravel road with an arable fi eld on one side and a meadow with thinly growing bushes on the other; an open location was selected for the measurement.
Th e third measurement point was a gravel road with coniferous wood with thinly growing bushes starting at 10 m from the road on both sides.
Th e fourth measurement point was an asphalt road with coniferous wood with thinly growing bushes starting at 10 m from the road on both sides.
Th e fi ft h measurement point was selected on an asphalt road going uphill with thinly growing bushes and single trees at 15 m from the road on both sides.
Th e sixth measurement point was selected on a gravel road going uphill with thinly growing bushes and single trees on both sides at 15 m from the road.
Noise level dependence on light vehicle speed was measured during summertime. Th e station was located leeward from the road. Th e wind speed was 1.2 m/s, air temperature 22 °C, relative humidity of 54%. In wintertime measurements were taken also leeward. Th e wind speed was 1.8 m/s, air temperature 6.3 °C, relative humidity of 44%. Fig. 3 shows the reciprocal and max noise levels of a car driving in an open area in wintertime and summertime. Noise levels were measured while a car was driving at a speed of 50 km/h on roads with gravel and AP. As we can see from the fi gures, upon moving away from the driving car by 7.5 m to 50 m, the reciprocal noise levels on roads with diff erent pavement decreased equally. Th e diff erence was 12 dBA in wintertime and 17 dBA in summertime.

Results of transport noise measurement
As seasons change so do the sound refl ections, especially when driving in wooded areas and changes also occur in coarseness of the road pavement. Th ese changes have infl uence on the fact that reciprocal noise level at a distance of 7.5 m in summertime is higher by 3 dBA than in wintertime. Upon moving away the noise level is higher in wintertime. Th e max noise level on roads with AP upon moving away from the driving car by 7.5 m to 50 m decreases by 17 dBA in wintertime and 19 dBA in summertime. Th e max noise level on the road with gravel pavement decreases by 16 dBA in wintertime and 17 dBA in summertime.
On comparing the levels of reciprocal noise on roads with diff erent pavements we see that noise level on roads with gravel pavement, when driving in an open area, is higher by 3 dBA in wintertime and summertime than it is on roads with AP. Noise caused by the tires and car vibrations is a consequence of pavement roughness. ment decreased by 16 dBA in wintertime and 24 dBA in summertime. Th is is infl uenced by winter and summer herbaceous vegetation which absorb and refl ect noise in diff erent ways. Th e diff erence was probably infl uenced by the noise absorption in the wooded area in summertime. Th e max noise level on roads with AP in the wooded area decreased equally by 22 dBA in summertime and wintertime. Th e max noise level on roads with gravel pavement decreased by 20 dBA in wintertime and 27 dBA in summertime.
Th e reciprocal and max noise levels at measurement points of 7.5 m and 20 m in the wooded area were higher in summertime than in wintertime. At the measuring point of 50 m, the noise level was higher in wintertime. Th e results obtained lead us to an assumption that refl ection from foliage of undergrowth and glade form a particular screen which prevents noise from being carried away. Fig. 5 compares the changes in noise spread in open and wooded areas upon moving away from the noise source by 50 m.
As we can see in Fig. 5 the reciprocal noise level in summertime is lower by 2 dBA than in wintertime. Upon moving away from the noise source by 50 m, motor transport produced reciprocal noise in wooded areas is lower by 6 dBA than in open fi elds (Fig. 5). Th e noise spread reduces equally both on roads with AP and gravel roads. All this shows that growing trees have fair infl uence on noise suppression.
Th e max noise level in summertime is lower by 1 to 3 dBA than in wintertime (Fig. 5). Fig. 6 compares noise levels produced by a car driving uphill on roads with asphalt and gravel pavement.
Th e results obtained show that the reciprocal noise level when driving uphill on the road with gravel pavement at a point of 7.5 m is higher by 4 dBA than on road with AP. Th is noise at a point of 50 m on road with AP is lower by 3 dBA than on gravel road (Fig. 6).
A light vehicle driving on the road with gravel pavement at a speed of 50 km/h up a hill with a steepness of 5% at a point of 7.5 m produces a noise more intense by 2 dBA than driving on open area at the same speed.  Th is time the reciprocal noise level on roads with AP upon moving away from the driving car by 7.5 m to 50 m decreased by 15 dBA in wintertime and 20 dBA in summertime. Th e noise level on the road with gravel pave- Fig. 7 shows the dependence of reciprocal and max noise levels on car speed when driving in an open area on roads with asphalt and gravel pavement in wintertime. As light vehicle speed increases from 40 km/h to 50 km/h, the level of reciprocal noise at a distance of 7.5 m from a car rises by 2 dBA. Upon moving away by 7.5 m to 50 m, the spread of the noise produced by a driving car reduces by 12 dBA.
Comparing the noise levels on roads with diff erent pavements we see that reciprocal noise level on roads with gravel pavement is higher by 3 to 4 dBA. Th is diff erence in noise levels occurs at all distances (from 7.5 to 50 m) from a driving car. Fig. 8 shows the dependence of reciprocal and max noise levels on car speed when driving in wooded areas on roads with asphalt and gravel pavement in wintertime. As light vehicle speed increases from 40 km/h to 50 km/h, the level of noise rises by 2 dBA. Upon moving away by 7.5 m to 50 m, the spread of a driving car produced noise on roads with AP decreases by 15 dBA and by 16 dBA on roads with gravel pavement.
A car produced noise on roads with gravel pavement in wooded areas in wintertime is higher by 3 dBA than on roads with AP. Fig. 9 shows the dependence of reciprocal and max noise levels on car speed when driving in an open area on roads with asphalt and gravel pavement in summertime.
Th e reciprocal noise level of a car driving at a speed of 50 km/h at a distance of 7.5 m on road with gravel pavement is higher by 3 dBA than on road with AP. When driving at a speed of 70 km/h, the diff erence is 2 dBA.
Th e diff erence of reciprocal noise level of a car driving in an open area at various speeds (from 7.5 to 50 m) can be seen in Fig. 10.
Th e results obtained show that upon increasing car speed from 50 km/h to 70 km/h, the reciprocal noise level, considering metering points, increases by 5 dBA to 7 dBA on asphalt roads and 4 dBA to 8 dBA on gravel roads.   Fig. 11 shows the dependence of reciprocal and max noise levels on car speed when driving in wooded area on roads with asphalt and gravel pavement in summertime.
As we can see, upon increasing speed from 50 km/h to 70 km/h when driving in woods, the noise level on sectors with AP increases by 3 dBA to 4 dBA and 5 dBA to 6 dBA on roads with gravel pavement.

Conclusions
Motor transport produced noise depends on the distance from the noise source, car driving speed, territory conformation and obstacles in the way of noise spread (herbs and woody vegetation).
Th e noise level on roads with gravel pavement when driving in an open area in wintertime and summertime is higher by 3 dBA than on roads with AP.
Th e noise level in wooded areas on roads with gravel pavement is higher by 4 dBA in summertime and by 6 dBA in wintertime than on roads with AP.
As light vehicle speed increases from 40 km/h to 50 km/h in wintertime the noise level has a tendency to rise by 2 dBA.
As car speed increases from 50 km/h to 70 km/h in summertime the noise level rises by 5 dBA.
Upon moving away from the noise source by 50 m a car produced noise in the open and wooded areas is lower by 2 dBA in summertime than it is in wintertime.