Abstract
Traffic noise is one of the main sources of noise pollution in cities. Around an 80% of the city noise is produced by vehicles. One of the current technological challenges is to achieve a sustainable acoustic environment in constantly growing cities with a rising quantity of vehicles. Current legislation obliges to determine the noise level of a vehicle according to a test procedure shown in Directive 70/157/EEC.
The maximum noise level has been declining gradually; however, this reduction has not affected the overall traffic noise. One of the reasons for this fact is that the approval test does not represent properly the real noise level emitted by a real car in real driving conditions. To determine the noise emission level more realistically, it is necessary to establish a pattern test that allows two things: controlling the main parameters that may affect such noise emission and reproducing the measurement conditions any time the test is performed.
In this work, a sample of vehicles has been instrumented to obtain physical measurements of the variables that can influence the noise emission level. Positions, velocities, accelerations (longitudinal and lateral) and time have been analyzed using a GPS sensor. Engine speed, engine load, throttle position and engine temperature have been studied through the vehicle CAN BUS and a battery of microphones has measured emitted noise in several points of the vehicle.
A circuit that represents the usual circulation in a big city like Madrid has been defined, as well as several vehicle models with great presence in existing fleet of cars. Several drivers have covered the circuit at different times of the day and previous parameters have been measured in each test in order to determine average values of behavior.
With these average values, it has been possible to define a pattern test that allows to estimate the noise emissions produced by a vehicle in real driving conditions. This pattern test will also allow to establish acceptable limits of such emissions.
KEYWORDS: Noise emissions; real driving conditions; pattern test