Acoustic assessment of a passing-by hybrid distribution truck

摘要

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