Off-peak low noise heavy-duty vehicles, façade insulation and indoor noise disturbance

Off-peak delivery of goods can result in increased transport efficiency, fuel savings, less pollution and increased traffic safety. However, unless carefully managed it causes increased annoyance and health risks for inhabitants exposed to the transportation noise during hours used for recovery and sleep. The presented work focuses on heavy-duty vehicles with Diesel engines during the "last mile" of the transport corridor through densely populated city centers. By using measured and simulated sounds, different driving conditions and acoustical treatments of vehicles and façade were studied at the façade and indoors in terms of 1/3-octaveband levels and judgments in listening tests. The evaluation shows that low-frequency noise of the vehicles is important indoors, while high frequency noise is the major contributor outdoors. Every apartment has low-frequency resonances, which have to be considered when defining basic sound criteria of the noise source and the building. According to the listening tests the low-frequency noise is coupled to the degree of reported arousal, indicating that reduced low-frequency noise is especially important at nighttime. It was concluded that an acceptable indoor environment was achieved with a modified truck that is driven by a responsible driver, and by using "noise proof" windows with higher sound insulation.