People make judgements of the sound produced by vehicles in a
variety of situations and contexts. The most common type of
assessment is an overall judgement of sound quality like
pleasantness and sportiveness. From the car manufacturer''s
point of view it is important to note that subjective judgements of
sound influence the buyer''s opinion of the performance and
value of the vehicle. Consequently, there is a need to quantify the
subjective perception of the sound quality associated with a
vehicle.
This paper presents a study of the sound quality of vehicle
exhaust noise based on the correlation between the subjective
perception associated with this type of sound and measured
psycho-acoustic parameters such as loudness, sharpness and
roughness.
The tailpipe noise of a selection of representative vehicles was
recorded using an artificial head. A subjective evaluation of these
sound recordings was made by a jury using standard relative
techniques. The data obtained from the jury was then statistically
correlated with measured psycho-acoustic parameters using multiple
regression analysis. As a result, we obtained a mathematical model
of the subjective response that can be used as a measure of sound
quality.
We finally used the model described above to define the spectral
targets associated with a desirable subjective perception for
tailpipe noise in terms of pleasantness and sportiveness. This
spectral targets are particularly useful for designing and tuning
exhaust systems for vehicles.