Abstract
Sound quality can be described as the relation between the perceptual reactions that reflect the customer’s acceptance of a product that generates sound. Initially, A-weighted sound level was the only parameter used in the acoustic assessment. Since the 1950s, psychoacoustic investigations have contributed to enhance the correlation between hearing sensations and objective parameters that define the sound. Nowadays, the application of sound quality in product design is widely extended in the industry, being considered an important field study by the main automobile manufacturers. This aspect has become as important as other specifications that define the vehicle (design, equipment, colour, price...). Therefore, sound quality would be considered as a distinguishing factor that could contribute to the car purchase decision.
This paper describes the development of a methodology to obtain a predicted model of acoustic annoyance applied to sounds of engines running on idle of compact cars, a feature that the customer can test in the car dealership in the process of purchase. Firstly, binaural recordings of eight car engines have been carried out by means of a digital artificial head placed on the seat of the driver. Main psychoacoustic parameters (level, loudness, sharpness, roughness...) were calculated. Afterwards, the design of a jury test was set up taking into account the kind of sounds to be evaluated. The recordings were presented to 12 subjects to assess the real sounds in a rate scale depending on the discomfort level perceived. The jury test was carried out in a laboratory where each subject listened to the recordings by means of headphones connected to an equalizer, making possible the reproduction of the sounds in an accurate binaural way and providing listeners with a realistic acoustic experience as if they were inside the vehicle. Finally, a model was established to predict the comfort rate for each sound using the psychoacoustic parameters as predictors.
This procedure can be useful for designers to validate the prototype until the acoustic satisfaction level is met and to assess a specific model with respect to the rest of existing products in the market.
Keywords: Sound quality, Psychoacoustics, Acoustic Comfort, Engine.