Effects of masking sound on train passenger aboard activities and on other interior annoying noises

Evaluation of masking effects in order to enhance the acoustical comfort in passenger train was made in an Inter-Regional train. Forty two subjects with equal number of males and females from three professional groups, namely students, employees and pensioners, participated in listening tests. The listening tests were administered in three sessions with (1) original background level, (2) amplified background level of 62 dBA and (3) amplified background level of 65 dBA. The first class compartment of a newly built Inter-Regional train was mounted with three pairs of loudspeakers for the reproductions of the amplified background sounds. The results revealed significant effects of masking in various aboard activities like reading, writing, concentrating, etc. as well as between the judgments of the professional groups. The results also indicated that the subjects were more annoyed in the presence of the original background level than in the presence of amplified background levels, especially in 65 dBA background level although the original sound pressure level was lower. Pensioners were more annoyed in all aboard activities compared to the other groups of subjects. Cellular phone conversations were still annoying to the passengers though they were less annoying if masked by the amplified background sound (especially by 65 dBA). However, the subjects reported that in the amplified background conditions they could still perceive that someone was talking but they could not hear what he/she was saying, which was not in the case of original conditions. There were no significant differences observed in perceiving the internal train noises such as brake, acceleration, rattling, squeaking, beating, etc. between masking conditions and also between the professional groups. This was due to the fact that the present Heat Ventilation and Air Conditioning (HVAC) system was not capable of masking the perceived internal train noises. The results also showed a tendency that the overall acoustical comfort became better with the amplified background sound despite of the higher sound pressure level inside the compartment up to 68 dBA.