Rumbling, humming, booming – Perception of vehicle interior noise at low engine speeds

Abstract

The reduction of fuel consumption of vehicles with combustion engines is a primary goal during the development of new vehicles. One approach to lower the fuel consumption is to reduce the engine speed. This changes the engine sound. Among others, low-frequency tonal components become audible. Sensations that are commonly associated with the perception of engine sounds with low-frequency tonal components are rumbling, humming and booming. Rumbling is characterized by a low-frequency tone that is amplitude modulated over time. Humming is elicited by an unmodulated low-frequency tone. The sensation of booming is an interaction of a low-frequency tone and modulated higher-frequency components. It is generally assumed that all these sensations have a negative impact on the pleasantness of the vehicle passengers, as they can cause tiredness and nausea. The present study investigates the influence of the stimulus characteristics on the above-mentioned sensations and the impact on the perceived pleasantness using psychoacoustic experiments. To explain the different sensations, artificial prototypical sounds were presented to the listeners prior to the experiment, which contained key stimulus properties for each sensation. The sensations were measured for recordings of vehicle interior sounds that were artificially manipulated to change the strength of the sensations. It is shown that not only the sensations change substantially but also the pleasantness, confirming a strong link between the sensations and pleasantness ratings. The results can form a basis for modeling these sensations and their impact on the pleasantness.