Highly refined NVH (Noise, Vibration and Harshness) is a key attribute for premium segment passenger cars. All noise sources such as powertrain, tires, wind, climate unit and etc. must be well balanced and at such a low level that the customer expectations are met or exceeded. However, not only are the NVH levels of importance but the character of the noise must also meet the high demands from premium car customers. This is especially true for diesel engines which historically have been more prone to have a less refined engine noise character than petrol engines.
This paper will describe an investigation of what is defined as “engine presence” in four-cylinder diesel engine cars. The scope is to define a method for consistent subjective assessment of engine presence and to find the relationship and investigate the correlation between the “perceived loudness”, “perceived harshness” and the overall engine presence interior of the car. A comparison of the results from subjective assessments when driving cars, and a listening study of the same sounds in a studio environment has been done. This was done to find the most consistent method and also avoiding bias from preconceived perceptions as for example influence of car model and brand.
Finally, a commercial tool has been used to investigate the correlation of psychoacoustic parameters and the perceived engine presence and to objectively define engine presence including a metric explicit for combustion noise. The result show a good correlation between subjective ratings and a multiple linear regression model.