Experiments are reported involving 14 subjects exposed to noise from 7 types of road surfacing. The subjects, chosen after audiometric tests, each received pre-recorded road noise from various types of road surfacings as they travelled over surfaces of known unevenness, in a medium-sized car. In the first of two experiments, the method of paired comparisons was used to examine the annoyance caused by road noise. Under normal driving conditions, each subject was presented, via a head phone set, with every possible combination of 7 road noise recordings in random pairs. It was found that subjects could readily distinguish between the various types of noise and were consistently able to place the noise from the test surfacings in rank order of annoyance. An increase in the level of surface unevenness over which the car travelled did not alter this rank order. A linear relationship between annoyance ranking and noise level db(a) was found. In a second experiment, a rating scale was used to assess both annoyance and overall riding comfort. as before, annoyance increased with an increase in noise level for a given level of surface unevenness. For the two different levels of surface unevenness examined, the results indicate that ratings of riding comfort by the test subjects were influenced by noise level. At low levels of noise the two levels of surface unevenness were given different comfort ratings by the test subjects; with increasing noise level, the comfort ratings for the two levels of surface unevenness converged. (Author/publisher)
Samenvatting