Impact of Ordinal Proximity of Frequency Components on the Auditory Perception of Engine Knocking

<div class="section abstract"><div class="htmlview paragraph">This study examines the acoustic properties of engine-knocking sounds in gasoline engines, arising from misfires during spark ignition that negatively affect driving performance. The aim was to understand the frequency characteristics of acceleration sounds and their connection to the proximity of the order components. The study also explores “booming,” where two different frequencies of sounds occur simultaneously, potentially linked to the unpleasant nature of engine knocking. Using a sinusoidal model, we generated engine acceleration sound models with 5th-, 10th-, and 15th-order components, including engine knocking. Two types of sound stimuli were created: one with the original amplitude (OA) and one with a constant amplitude (CA) for each component order, emphasizing the order-component proximity in CA sounds. Aural experiments with 10 participants in an anechoic room using headphones and the MUSHRA method revealed an inverse relationship between OA and CA ratings as the component order increased. OA typically produced better evaluations, possibly owing to the reduced high-frequency components preventing booming, whereas CA received lower ratings owing to pronounced booming from a constant amplitude. Overall, OA significantly outperformed CA, likely because the reference tone also contained the original amplitude data. This study confirms the significant impact of order-component proximity on auditory perception, such as booming. This suggests that the original amplitude information improves sound quality. We aim to further explore this relationship and analyze engine-knocking sounds in more detail.</div></div>