In recent years, car manufacturers have been shifting their efforts towards improving quality of interior noise, rather than simply reducing noise levels. One of the most important issues, which is today widely accepted, is that noise contains information. Slamming noise should warn us that doors are safely closed, control panel pushbutton “clicks” inform us about the correct turning on of devices, etc.. One of the acoustic researchers' task is therefore to modify the original noise to emphasize quality of information and to reduce annoying components. For these reasons, it is very important to affect noise timbre, by investigating the relationships between mechanical and acoustical parameters.
In this paper we describe a workstation (which we have called N.O.T.E.: Noise Optimizator for Thermal Engine) for intake and exhaust system noise synthesis, that integrates an acoustical simulation code with a synthesizer. By means of this flexible system, it is possible to lay out the engine acoustical model, starting from physical laws and using a few general purpose predefined blocks (such as noise sources, resonators, filters, etc.) in a CAD environment. The most important feature of the sound synthesis workstation is the possibility of changing all parameters in real time, making it feasible to “play” every kind of engine noise, before building any prototype.