Long-Term Trends in Manufacturer-Declared Interior Noise Levels of Agricultural Tractor Cabs

Interior noise levels in agricultural tractor cabs play an important role in operator comfort and long-term occupational exposure. This study investigates long-term changes in manufacturer-declared interior noise emission levels of agricultural tractors using catalogue data published in 2015 and 2024. Instead of relying solely on average values, the analysis focuses on changes in the statistical structure of noise level distributions, including dispersion and percentile-based indicators, in order to identify population-level technological trends in cab acoustic performance. The results reveal a clear structural shift towards lower declared noise levels accompanied by reduced variability across tractor models. Reductions of approximately 1-2 dB(A) are observed at lower and intermediate percentiles, together with a narrowing of the interquartile range, indicating increasing convergence of baseline acoustic performance across manufacturers. Elevated values persist at the upper tail of the distributions, reflecting the continued presence of high-power and specialised tractor configurations rather than deterioration of modern designs. The findings suggest that recent improvements in tractor cab acoustics are primarily associated with structural changes in the tractor population and the gradual elimination of acoustically unfavourable configurations. Although manufacturer-declared values cannot replace field measurements, the catalogue-based approach provides a consistent framework for identifying long-term technological evolution in agricultural machinery acoustics and complements experimental research by offering a macroscopic industry-level perspective.