Development of an Audio Assessment Module

Development of an Audio Assessment Module: For Sound Engineering of Aircraft Designs

Mehmood, Umair (TU Delft Aerospace Engineering)

Snellen, M. (mentor)

Delft University of Technology

Aerospace Engineering

2018-07-09

A first step in designing aircraft with optimal sound is the development of a module that is able to assess noise in a sophisticated way, which is the exact goal of this research. In this research the Audio Assessment Module (AAM) is completed with the addition of tonality, roughness and fluctuation strength. The AAM is now able to assess sound in terms of five sound quality metrics, specifically loudness, tonality, roughness, sharpness and fluctuation strength, but also in terms of conventional metrics such as EPNL. The five sound quality metrics can be combined to form a psychoacoustic annoyance value PAmod. The AAM is applied to a variety of sound recordings, including 255 measured aircraft flyover measurements of 26 different types of aircraft, in an attempt to find relations between design variables and the five sound quality metrics. The only significant correlations observed are those of the wingspan, wing loading and engine diameter with loudness. High values for roughness are observed for helicopter sounds due to the buzzing sound produced by the helicopter rotor, indicating that roughness is an important metric for propeller aircraft or aircraft with open-rotor engines. Listening tests, with the aim of learning whether the psychoacoustic annoyance value is a better annoyance predictor than EPNL, were conducted in which twenty subjects participated. From the listening tests it was found that the metrics did not outperform each other in terms of annoyance assessment. However, some deficiencies of the PAmod metric came to light during the listening tests. For a valid comparison of two sounds in terms of PAmod the duration of the sounds has to be the same, since the values "exceeded 5% of the time" are used in the calculation of PAmod. It was also found that the loudness contribution to PAmod might be too high. More research into PAmod can potentially improve correlations with subjective evaluations. The ultimate aim of an audio assessment module is to use it for sound engineering of aircraft designs. The sound quality metrics are capable of capturing the different characteristics of sound in a more comprehensive manner than for example EPNL. Differences in sound for current aircraft or future concepts such as aircraft powered with open-rotor engines can be captured by the individual metrics. This can then be used for sound engineering of aircraft designs in which the design is modified in such a way to arrive at a sound which is as close as feasible to the target sound. In this way, it is possible to design aircraft which sound inherently more acceptable and reduce the annoyance caused to residents by aircraft noise.

sound engineering
audio assessment module
psychoacoustic annoyance

http://resolver.tudelft.nl/uuid:4ea3537e-171c-4692-ae58-95e5dff0d406

Student theses

master thesis

© 2018 Umair Mehmood