Article,
An investigation on time-interval optimisation of traffic noise measurement
Journal of Low Frequency Noise Vibration and Active Control, (2006)
Abstract
Noise is one of the most important sources of pollution in metropolitan
areas, it causes discomfort for urban residents and hampers the efficiency
of the work force. Currently, there is an urgent need to conduct
basic studies on this issue in order to attain a mathematical model
for prediction of traffic noise levels in the major cities of Iran.
This article is the result of research conducted in the city of Hamadan
in 2005 with the ultimate objective of setting up a traffic noise
model based on the traffic conditions of Iranian cities.For this
study, main access roads of Hamadan city were divided in 64 segments
and after careful considerations, 94 measuring stations were assigned
to them. For the optimisation of noise measurement intervals in each
station and the determination of background noise impact on the main
traffic noise, 30 stations with the specifications of the target
stations were randomly selected at the pilot stage. In all the pilot
stations, the background sound pressure level (SPLb), Leq, SPLmax,
L10 were measured simultaneously in 10, 30 and 60 minute intervals
(in random non-holiday days at random hours). The measurements were
made 3 meters away from the road side.Pilot results indicated that
the mean equivalent sound pressure levels at the measuring stations
in 10, 30 and 60 minute intervals were 70.76±2.11 dBA, 30 minutes
70.88±2.19 dBA, and 60 minutes 70.93±2.13dBA respectively. The mean
background sound pressure level at the stations was 60.77±5.04 dBA.
The results of the traffic noise measurements at the research stations
through the comparison of mean values (Variance Analysis) indicated
that there is no meaningful deviation between the Leq in the above-mentioned
time intervals (10, 30 and 60 minutes) in the hourly measurements
(P= 0.998). In the pilot phase, it was determined that the background
noise level did not impose a considerable impact on the main traffic
noise and it was possible to make 10-minute interval measurements
to forecast the 30-minute and 60-minute interval equivalent levels.
Therefore in the main phase of study with the utilisation of the
10-minute interval results collected from each of the 94 stations,
a total of 282 measurements including 2 daily-hour and one nightly-hour
measurements were conducted. The final results revealed that the
average Leq in all stations was 69.04±4.25 dBA, the average speed
of vehicles was 44.57±11.46 km/hr and average traffic load was 1231.9
± 910.2 V/hr.Moreover, the results indicated that the Leq in the
studied roads were exceeding the allowable levels of urban noise
pollution and there was a meaningful deviation between equivalent
levels during a 24-hour period, traffic load and various vehicle
speeds (P= 0.003).
