Acoustic assessment of a passing-by hybrid distribution truck

摘要

In relation with traffic restrictions and congestion within cities during daytime hours, the“last kilometer” for goods delivery turns out to be problematic. Hybrid trucks may be aworthwhile solution, especially for activities at very early or late hours. Apart from somenoise reduction figures put forward by manufacturers or concerned users, the actual noisebenefit of these vehicles is not well known. The present study assesses the noise emission ofone hybrid distribution truck, either in hybrid or electric mode, over wide real usageconditions, and compares it to an equivalent full thermic truck. Constant speed pass-bys aswell as accelerating or braking phases are tested. Measurement includes third-octave andglobal standard 7.5 m noise levels, noise source analysis resulting from microphone arrayprocessing, and vertical directivity. The truck in hybrid mode comes out to be a little lessnoisy than the full thermic one at constant speeds, but deteriorates when accelerating,mainly due to drive tire characteristics. The electric mode benefit exceeds 8 dB(A) at lowspeed, reduces at higher speeds and vanishes beyond 50 km/h. Due to dramatic motor noisereduction, the drive wheel rolling noise becomes then the main noise contributor over thewhole usage range. Moreover the electric mode results in lower directivity in upwarddirections (building storeys).