Excavator Exterior Noise Contribution Analysis using Angle-Based Operational Acoustic Load Synthesis

<div class="section abstract"><div class="htmlview paragraph">Exterior noise (EN) regulations for earth-moving machines (EMMs) require original equipment manufacturers (OEMs) to develop noise mitigation solutions early in the design process. Predicting the effectiveness of these solutions at this stage, however, is challenging. Excavators differ from other EMMs due to their rotating upper frame, which operates atop a fixed lower frame. Regulations such as ISO 6395 and EC/2000/14 mandate specific operating maneuvers, where noise sources dynamically change their position, directivity, and speed throughout the operating cycle. This complexity makes noise contribution analysis more difficult, as it must account for variations in angular position and operating conditions.</div><div class="htmlview paragraph">While previous studies successfully applied Acoustic Source Quantification (ASQ) and contribution analysis to linearly moving EMMs, the angular motion of an excavator’s cab with respect to fixed target microphones introduces additional data processing challenges. This study addresses these challenges by employing frequency-domain ASQ for operational noise source quantification. The source strengths calculated in ASQ are treated as invariant due to its weak coupling with the surrounding air medium. The invariant nature of the source strengths allows its use in ‘what if” scenarios of machine topologies. Following ASQ, a frequency-domain virtual prototype sub structuring (VPA) approach was used for contribution analysis. The VPA method enables source swapping and “what-if” scenario simulations, allowing OEMs to evaluate potential noise mitigation strategies. To demonstrate the potential use of simulation approach for front loading of design effort for mitigation studies, an acoustic model of the excavator was developed. Source-to-target transfer functions were computed as a function of angular position of cab’s upper frame. These synthesized Acoustic-acoustic AA-FRFs (AA-FRF) were validated against test data. These validated transfer functions in conjunction with computed acoustic source strengths were then used to demonstrate noise contribution analyses and the practical applicability of the proposed methods. The study was conducted on a stationary excavator following an ISO 6395 required operating condition when the cab and boom follows a 90 degrees cyclic motion on one side of machine. The results highlight the practical potential of the proposed methods in advancing noise mitigation strategies early in the design process.</div></div>