Aircraft sound quality as Pareto ranking criterion in multi-objective MDO

The paper deals with the use of sound quality as a criterion for the ranking of the non--dominated solutions of a multi--objective design optimization of aircraft oriented to environmental sustainability. The solutions belonging to the approximated Pareto front of the bi--objective minimization of the fuel burned and the noise level at certification points are ranked with respect to the matching of the emitted noise spectrum against a reference target sound. The latter is a synthesized aircraft sound satisfying sound--quality specifications coming from psychometric tests conducted in the EC--funded projects (Sound Engineering for Aircraft) and COSMA (Community Oriented Solutions to Minimize aircraft noise Annoyance). Indeed, the environmental impact of civil aviation is nowadays the most urgent concerns in the development a sustainable air transportation system since, during the last three decades, the air traffic growth has generated a remarkable increase of the operative airports. In parallel, the urban development has led to the inclusion of secondary airports within the city areas. As a consequence, the number of people directly exposed to aircraft noise has sensibly increased. In such a social context, the designers can hardly attain further substantial technical improvements as the standard concepts and technologies have reached a development saturation, thus imposing the identification of breakthrough technologies and innovative concepts, with a plausible date of entry into service not early than 2050. The research initiated in SEFA and further developed in its follow--up COSMA aims at the alleviation of the noise impact on the population, switching the attention on noise quality rather than noise level, in order to provide to designers additional tools to mitigate the effects of noise. The present work is the evolution within a multi--objective context of the early attempts of sound--quality-- oriented MDO developed during those projects.