Pass by Noise Analysis Method Extended for Mitigation Solution Development on Earth Moving Machinery

Pass-by/exterior noise of earth moving machines (EMM) and forestry machines is becoming a focus at early product development stages. ISO 6395 (2) or EC/2000/14 (1) standards defines exterior noise test procedure for EMM. However, these standards do not provide insights for diagnosing any noise issues which may arise. The analysis challenges are posed by the moving machine and acoustic sources with respect to the stationary hemisphere target microphone on the ground and changing operating condition of sources as function of time. There is need to develop a seamless methodology to identify acoustic sources, quantify respective source strengths and rank partial contributions from each source to the total target microphone response in order to overcome the aforementioned challenges. This paper demonstrates use of time and frequency domain Acoustic Source Quantification (ASQ) combined with time domain overall sound pressure level computation to mimic operational test conditions which provides the ability to demonstrate partial contribution of each acoustic source during simulated exterior noise test run.

The work was performed on a four-wheel drive Loader (4WDL) machine. This analysis approach provides quantified insights for the design team for overall machine noise improvements. To increase the value of such a method in the early design stage, an acoustic simulation model of a machine is developed, and a response analysis is demonstrated using the computed ASQ based results. The model is planned to be exercised for “what if” improvements based on contribution analysis. The physical modifications developed based on test results are implemented and tested for their effectiveness.