Towards a low noise truck specification
This report summarises the most important findings in the research project Quiter Transport for More Efficient Distribution aiming at the outline of a sound characterisation specification for noise improved heavy-duty trucks for nighttime distribution of goods. The focus in the project was on the "last mile" of the transport corridor through densely populated city centres, i.e. transport through rather narrow street canyons lined with residential housings. The noise of the loading or unloading of the goods at the destination is beyond the scope of the project. Section 2 gives the general description of the involved elements; the outdoor truck sound source, the street canyon amplification and reverberation, noise reduction by windows and facades, and the indoor noise levels due to a truck passing by in the street. Section 3 gives some specific results from the project; the results of the modifications of a truck with the purpose to reduce outdoor and indoor noise evaluated by measurements. Section 4 summarises the results of the listening clinics; including fundamental and specific results test subjects evaluating their response to real and synthesised outdoor and indoor sound of a heavy-duty truck, a light-duty van and the modified heavy-duty truck. Section 5 discusses, from various perspectives, sound attributes of a low noise truck suitable for nighttime distribution of goods. Finally, Section 6 gives the conclusions in a concise format.