Sound pleasantness of electrically adjustable exterior mirrors in vehicles

Consumers increasingly demand high quality products, forcing manufacturers to a greater effort when designing. During the last years, the noise has become a key factor in valuing a product, so the use of psychoacoustic techniques has been extended considerably. The automotive sector has always taken into consideration the noise when designing vehicles. A large number of tools and analysis methods have been developed in order to determine the sound quality of their products. Although the first efforts focussed on establishing the sound quality of the propulsion system, they rapidly spread to other parts of the vehicle like doors, powered windows, etc. The present work focuses on studying the behaviour of electrically adjustable exterior mirrors in vehicles. In order to analyse the noise produced by this kind of devices, four different samples were measured in a semi-anechoic chamber. To establish the pleasantness descriptor of the samples, sixty-two subjects were exposed to an auditory test using two different methods: paired comparison and ranking procedure. The experiments were carried out in three different laboratories: University of Kyushu in Japan (JP), University of Coimbra in Portugal (PT) and University of Alicante in Spain (SP); leading to a cross-cultural study. The results showed a great similarity between the preferences obtained by the two methods.