Time-Frequency analysis applied to psychoacoustic evaluation of car engine Noise Quality

A novel approach to the widespread problem of evaluating the “quality” of noise of a car engine is presented. Traditionally some psychoacoustic parameters of the sound are calculated and used to generate a certain Noise Quality Index (NQI) according to a previous jury assessment. Once the NQI is validated, new noise recordings can be evaluated and automobile engineers can estimate how the perceived quality varies as engine working conditions change. In this paper we relate well-known psychoacoustic features - which usually contribute to generate the NQI - to Time-Frequency (TF) characteristics of diesel noise, in order to find relations between both kinds of parameters. These relations could help engine designers to predict the noise quality just analysing the spectral changes of the noise waveform. Some promising results are showed involving a diesel engine belonging to the luxury class of an European car manufacturer.