Truls Berge, SINTEF ICT Dept of Acoustics
Asbjørn Ustad, SITNEF ICT Dept of Acoustics.
truls.berge@sintef.no
A monitoring station has been developed
to measure the pass-by noise emission levels of individual vehicles in normal
traffic. The monitoring station measures the noise levels, the speed of the
vehicles, classification (based on length) and direction of travel (lane). In
addition, a weather station is included with a surface detector (wet/dry). This
means that all emission levels can be related to meteorological parameters such
as temperature, wind direction/speed, and if the surface is wet or dry. In addition
to individual noise levels (LAmax), 1 hr/24hr LAeq/Lden-levels and 1/3rd octave
band frequency spectra from 25 Hz to 10 kHz are also measured.
As a first test of the monitoring
station, over 34 000 vehicles have been monitored at one location only; a dual
lane road with posted speed 60 km/h. The analysis of the data makes it possible
to compare the noise contribution of different categories of vehicles to the
overall equivalent levels, the influence of a wet road surface, etc. In
addition, a simulation has been done, to study the effect of removing the moist
noisy vehicles away from the fleet, for example all passenger cars with levels
above a certain limit. As a first test, removing all passenger cars with
emission levels above 85 dB(A) (about 2-4% of the passing cars at this
location) will only reduce the 24hr equivalent levels in the region of 0.5 – 1
dB(A). However, if the limit is set to 80 dB(A) (about
22-25% of the cars passing this level), a reduction of 3-4 dB(A) can be
achieved.
Preliminary results show that a wet
surface gives an increase in spectral levels above 1 kHz for passenger cars and
only increase the overall levels in the area of 1-2 dB(A).
The study was part of the EU-project
SILENCE.