Driving parameters for annoyance of Buzz Saw Noise in Aircraft Cabin

Multiple Pure Tone Noise (also described as buzz) is a noise audible in the cabin of many turbofan powered aircraft for a short time in the beginning of the climb phase. The noise consists of tones and is unique for each engine and aircraft type. The spectral envelope is defined by its tone to noise ratio, the fundamental frequency, the slope towards high frequencies, Blade Passage Frequencies (BPF) prominence and spectral notches. The impact of this shape on the perception of the MPT noise is currently unknown. The aim of this presentation is an analysis of the spectral characteristics as driving factors of the unpleasantness of the noise.Six measurements performed on different aircraft were used to gain an overview over the spectral content and phase information of the noises. This was used as an input for a software tool to synthesize MPT's and background noise in for the test desired manner. In a listening test 38 participants evaluated 18 synthesized sounds. The stimuli were adjusted in two adaptive paired comparisons to be equally preferred or perceived as loud as a reference cruise noise. The level differences between MPTs and the reference sound are a measure of the preference/loudness judgement.