Calibration of subjects with master scaling: An application to the perceived activity disturbance due to aircraft noise

The aim of this study is to assess whether or not rating perceived activity disturbance using magnitude estimation scale and using master-scaling transformation is more relevant than rating disturbance with category scale to reveal the influence of the number and the sound quality of aircraft flyovers. The master-scaling transformation is intended to reduce the inter-individual differences between people. Thirty participants were subjected to six sound sequences. They attended the test in two different sessions separated by a week at least, and had to evaluate the level of activity disturbance due to the noise environment when carrying out memory and concentration tasks. During each session, participants first went through a calibration phase and were then subjected to one 20-min sound sequence. The calibration phase, which can be also considered as a training phase at the beginning of each session, allows subjects to built their own annoyance scale. As expected, the perceived activity disturbance depends on the equivalent sound level and on the number of aircraft. But the master-scaling transformation did not succeed in reducing the variability between subjects. This transformation which calibrates the subjects on only one aspect of the sound (which is the equivalent sound level in this experiment) could emphasis the difference between subjects who have been more or less sensitive to other aspects of the sound (the tonality or the repetition of events in this experiment) than to loudness. Nevertheless, this experiment confirms that Stroop reaction time, which is influenced by the number of flyovers, seems to be adapted for measuring the effect of noise on task achievement.