Impact of low frequency road traffic noise on indoor environments for different facade structures

Sammanfattning

Road traffic noise is a major environmental problem in Europe where at least 20percent of the EU population live in areas where traffic noise levels are harmfulto health. Recent changes and regulations in Swedish law enables a higher soundpressure level at facade, making it easier to build closer to roads. Typical noise reductionmeasures improve sound insulation at mid and high frequencies well, whilenot being as effective at lower frequencies of 20–200 Hz. As a consequence, morelow frequency traffic noise indoors can be expected as we build closer to traffickedstreets. This thesis aims to investigate the effect of low frequency traffic noise insidedwellings where (1) a study of traffic modelling and field measurements on a selectionof different facade structures is made to determine the indoor low frequencytraffic noise and (2) a psychoacoustic study is carried out where the annoyance levelfrom low frequency traffic noise is investigated through listening tests.The measurements suggest that none of the studied apartments have good insulationfor low frequency noise. For all of the studied facades, peak pass by sound levelsdue to heavy vehicles are above our audible threshold and also at certain frequenciesabove the recommended Swedish guidelines for indoor low frequency equivalentlevels.The listening test suggests that the largest annoyance for inhabitants inside dwellingscomes from heavy vehicles while light vehicles pose no greater annoyance even if thepeaks of the low frequency sound levels inside the dwelling are above the equivalentlevel guideline values. Furthermore, the listening test results suggest that the annoyancethat inhabitants experience is not only from low frequency components fromvehicles passing by at a constant speed with no significant tonal changes. Insteadthey suggest that the low frequency components constitute the annoying part whenthere are clear tonal changes such as in situations with accelerating vehicles.