Assessing the railway bonus in laboratory studies

When the subjective impressions of traffic noises with the same values of L_Aeq are compared, it is often found that rail noise is judged to be less annoying than road traffic noise or aircraft noise. The present experiments were designed to examine the so-called 'railway bonus' in laboratory situations. 15 minute noises which contained several events of road traffic noise and/or rail noise were used and their instantaneous loudness as well as overall loudness were judged by German and Japanese subjects. It was confirmed from the results that there may exist a railway bonus in the judgments of loudness also in laboratory situations. That is, the rail noise was judged to be softer than road traffic noise by the both groups of subjects even if the L_Aeq values were the same. Possible reasons for the existence of the railway bonus may be the difference in frequency components, frequency of events, subjective meanings, etc. between both sound sources. Further systematical and detailed experiments are needed in order to determine the magnitude of the railway bonus as well as its underlying mechanism.