Predicting Noise from Mower Deck using a Computational Aeroacoustics Model

Noise from lawn mowers is important for operators hearing protection. Majority of lawn mowers do not feature a cab thus requiring costly noise absorbent headsets. Noise emitted by a lawn mower is closely related to its cutting efficiency because blades must rotate at high speed to lift and cut the grass. For a low noise lawn mower design, it is critical to develop an accurate virtual model to predict the noise level precisely. Most of the noise from lawn mowers is generated by the interaction between the rotating lawn mower blade, deck, and surrounding air. To predict its noise level a Computational Aero-Acoustics (CAA) model is used based on a commercial Computational Fluid Dynamics (CFD) software. A DES solver along with a FW-H far field propagation method is used to calculate the transient flow pressure field and the corresponding flow-induced noise radiation. The noise test with the lawn mower is performed in a semi-anechoic chamber and the sound power level between the CAA and the experimental results are compared. Excellent comparison between the CAA model and the test shows that this process can be used for future evaluation of low noise lawn mower design and protect operators from high noise.