Impact of intermittent helicopter noise on passenger cognitive performance

Abstract

Internal helicopter noise is one of the most unpleasant due to its high intensity, superior to any other transportation means (often above 110 dB). A top objective for the helicopter industry is to improve the acoustic comfort within the cabin to meet the growing demand from the passengers who would like to work or relax comfortably during a flight, and without hearing headsets. Noise has an undeniable impact on human states, either negative or positive. Its effects on cognitive performance depend mostly on the type of sounds. Some studies showed that intermittent noise can have deleterious effects on working memory (eg. Salamé and Wittersheim, 1978) or positive exciting effects during monotonous tasks (Lundberg and Frankenhaeuser, 1978). This study is a follow-up to a previous experience that assessed the extent to which quite continuous but intense helicopter noise could be detrimental to passengers’ cognitive performance (Jahanpour et al., 2019). The latter suggests that short expositions (5 minutes) to continuous helicopter noise were not deleterious to mental calculation, reasoning, and working memory. The purpose of this study was to explore the effects of intense and intermittent helicopter noise on the same cognitive functions. To better understand the impact of this intermittent noise on cognitive performance and passenger comfort, subjective, behavioural, and cardiac (ECG) measurements were used. To simulate passengers’ working activity, three tasks were selected: the Toulouse N-Back Task (TNT, combining mental calculation, reasoning, and working memory; Mandrick et al., 2016), a reading task, and finally the Mackworth Clock-Test (a vigilance task; Lichstein et al., 2000). Three conditions were performed to analyse the effects of helicopter noise: first, a silent condition, then a condition with continuous and stationary helicopter noise (controlled to 80 dB(A)), and a last condition with intermittent helicopter noise (integrating successions of take-offs and landings; controlled to 80 dB(A)). Results showed that the subjective measurements were negatively impacted by the two helicopter noises conditions, but more importantly by the intermittent noise. The intermittent noise was perceived as more annoying, distracting, tiring, and stressful than the stationary noise and the silent condition. Calculation and reading performance were not impacted by the noises. However, the vigilance task performances were globally affected by noisy conditions, resulting in more errors. Cardiac activity was also impacted by the two noises conditions, regardless of the task performed, revealing a slight increase in the heart rate during noisy conditions. This result may suggest that participants made a higher cognitive effort to cope with the stressing or distracting effects of noise. To conclude, this study shows that there is an overall effect of noise versus silence on the subjective feeling, the vigilance performance, and the heart rate. This suggests that monotonous task is more impacted by intermittent noise, even over a short period, than mental arithmetic and reading tasks. Intermittent helicopter cabin noises seem to have stronger influences than continuous ones on the subjective, behavioural, and physiological state of passengers.