TNAR - a new method for assessing road noise annoyance level

According to current standards, the impact of road traffic noise is represented by the Aweighted energy-equivalent sound level (L sub A,eq). This quantity is easy to estimate but does not take account of subjective annoyance of sound events. Using a dummy head measurement system (HEAD acoustics) the speed of each vehicle and the pass-by noise of different vehicles with variable speed profiles were binaurally recorded on characteristic road sections. More then 200 persons were subjected to a hearing test with different vehicle ensembles. The “annoyance effect” of different sound ensembles was rated using a “personal noise ranking scale” (PNRS) from “less annoying” to “very annoying”. In parallel, the psychoacoustic parameters loudness, roughness, sharpness, tonality and fluctuation strength were analysed and compared with the L sub A,eq. Results reflecting annoyance obtained with PNRS were combined with objective psychoacoustic parameters to an index defined as Traffic Noise Annoyance for Roads (TNAR). This new TNAR index represents a decided improvement upon the description accuracy of noise impacts on humans and enables engineers to construct road environments which not only reduce sound levels but, more importantly, reduce perceived annoyance to humans. Noise abatement in the future will not only be a quantitative problem, but also a qualitative solution.