Public acceptance of helicopters - The virtual noise component

Abstract

A detailed study of noise complaints in the UK and USA makes it clear that the level of public acceptance of helicopters and heliports is generally low. It has been shown that helicopters operating in some areas are considered up to 15 dB(A) more annoying than fixed-wing aircraft. A review of case histories, press reports, information collected by industry associations together with a study of the various factors involved shows that the level of public acceptance can be considered to be a function of both acoustic (direct) noise and a non-acoustic element, termed virtual noise. The magnitude of the virtual noise component is not directly related to either the absolute level or to the character of the noise generated by helicopters, but it is triggered by the acoustic signal. Moreover, the effectiveness of helicopter noise in triggering the virtual noise element would appear to be more dependent on the subjective character of the sound than its absolute amplitude The results of a number of studies show that the subjective reaction to the noise characteristics of the source and the virtual noise are of equal or even greater importance than the maximum noise level. It follows that attempts to address adverse reaction to helicopter operations by reducing acoustic noise at source or by traditional operational methods and without taking into account the impact of virtual noise, will be largely ineffectual. The importance of taking virtual noise into account when addressing the public acceptance of helicopters is discussed in the paper.