Human responses to the tonalness of aircraft noise

A study was conducted to examine the influence of changes in tonalness on annoyance ratings of aircraft noise. Stimuli used in this study were simulated using a program in which aircraft noise was decomposed into noise and tonal components. From these base components, additional aircraft sounds were created by varying the amplitude of the tonal components in a controlled manner while leaving the other sound attributes relatively unaffected. Two sets of 11 stimuli were generated based on a recording of a flyover after take-off event of an Airbus-310 aircraft. In Set A, tonalness was varied while loudness was kept nearly constant. In Set B, both tonalness and loudness were varied. Forty subjects aged between 19 to 33 years from a university population were recruited for this test. In the test, subjects rated the two sets of stimuli on an annoyance scale. Tonalness of these sounds, as predicted by using Aures’ Tonality model, ranged from 0.01 to 0.40. The range was little broader than the range we found in a set of around 40 aircraft recordings around two Florida airports. Many of the subjects were found to be sensitive to tonalness changes. In Set A when only the tonalness was increased, a significant increase in annoyance ratings was observed. It was also found that the loudness influenced the annoyance ratings significantly, when both tonalness and loudness were varied, but that tonalness still influenced the ratings. Average annoyance ratings were highly correlated to metrics that take into account both tonalness and level. It appears from the results that inclusion of tonalness in environmental noise metrics should be considered, but that large-scale community surveys including noise measurements should be conducted to determine the form that the tonalness-level metric should take.