Nowadays the automotive industry focuses more and more on the reduction of disturbing noises in the passenger compartment of cars of every type. A convenient car can not be imagined without a comfortable and silent interior. With the wider-and-wider spread of electromechanical servo systems for steering applications the amount of significant noise sources in the engine compartment (electric motor and belt drive of the servo system) icreased as well. In order to fullfill the strict requirements from the OEMs for the noise of the steering system, there is a strong need for investigating the structure-borne and airborne noise of the product in all project phases.
In order to accomplish the above mentioned task, the acoustic measurements and the subjective rating sessions take place in a reflexion free test room, in an anechoic chamber. Of course the more realistic the test environment, the more reliable the objective and subjective test results will be.
The topic of this thesis is to develop a method to reproduce the idle noise of the combustion engine in the passenger compartment as realistic as possible by means of loudspeakers. The main objectives of this work are therefore: understanding the conditions under which the above described problem is solvable, showing a practical approach for engine noise reproduction and describing an easy process that allows the test engineers to reproduce the engine noise in various vehicles.
The existence of such a method would allow the acousticians to judge the noise of the steering system together with different masking noises, hence getting a better picture of the product performane and accelerating the acoustic testing procedure. A high quality background noise reproduction method also allows the engineers to use less sophisticated test environment, e.g. an anechoic chamber without a high performance exhaust gas suction system.