A systematic evaluation of helicopter cabin noise: Case study of Robinson R44 RAVEN II

This paper presents a comprehensive test and systematic evaluation analysis of cabin noise in the Robinson R44 RAVEN II helicopter. Initially, microphones were placed within the cabin to conduct systematic assessments of noise levels under various flight conditions, including takeoff, climbing, level flight, landing, hovering, etc. Subsequently, time–frequency analysis was conducted on the test data utilizing traditional A-weighted sound pressure levels, which was followed by quantitative comparisons across different flight conditions. Then, detailed evaluation and discussion were conducted, taking into account the subjective perceptions and communication challenges of cabin crew members. This assessment incorporated the use of aviation noise indicators, speech interference levels, and metrics related to sound quality. Finally, potential noise reduction measures and their effects were preliminarily discussed. The results indicate that helicopter cabin noise exhibited variations across different flight states or positions within the same state, ranging from 87.6 dB(A) to 92.6 dB(A). Discrepancies between A-weighted sound pressure level and psychoacoustic parameters were observed, particularly during hovering states, which indicate that there is a necessity for the combination of multiple evaluation indicators. Notably, damping measure can serve as a pivotal factor in mitigating cabin noise.