## MONITORING OF NOISE EMISSION LEVELS OF INDIVIDUAL ROAD VEHICLES

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.