NOISE EMISSION ANALISYS AF A DMU TRAIN

The acoustic characterization of a DMU (diesel train) is presented. This work belongs to a collaboration of DIAS and TENITALIA in the 6th framework programme Project called “Silence” targeted to control urban traffic noise. The attention was focussed on the determination of noise emission both in stand still and running condition. To best understand DMU’s impact on urban areas measures campaign was divided into two steps, measures of sound Intensity in stand still condition, and noise sources localization by a linear array of microphones in pass by measures. Sound Intensity measures were made at two different engine’s rpm, 850 rpm and 1300 rpm, in this condition were also made measures of sound directivity of the air intake engine grill and of the exhaust gas muffler by the use of the intensity technique (major noise sources in stand still condition). Pass by measures were made at two speed condition 40 and 60 km/h. By the use of this method it was possible to detect the most relevant noise sources and their typical spectrum. These investigations were addressed to well identify the genesis and propagation of noise of this class of vehicle to finally individuate the most critical ones on urban and suburban areas.