Application of subharmonics for active sound design of electric vehicles

Abstract

The powertrain of electric vehicles generates an unfamiliar acoustical environment for customers. This paper seeks optimal interior sound for electric vehicles based on psychoacoustic knowledge and musical harmonic theory. The concept of inserting a virtual sound, which consists of the subharmonics of an existing high-frequency component, is suggested to improve sound quality. Subjective evaluation results indicate that the impression of interior sound can be enhanced in this manner. Increased appeal is achieved through two designed stimuli, which proves the effectiveness of the method proposed.

Noise and Vibration in Switched Reluctance Motors: A Review on Structural Materials, Vibration Dampers, Acoustic Impedance, and Noise Masking Methods

“…Addition of a random broadband noise may increase the overall loudness. On the other hand, addition of a random narrowband noise may increase sharpness [146]. Sharpness is a psychoacoustic sound quality metric that compares high-frequency energy levels to the total energy.…”

“…So, musical harmonic theory can be applied to identify the correct harmonics that need to be added to make the noise more pleasant [147]. Sound design for an electric vehicle is a relatively new issue for the automotive industry, so customer expectations are not defined yet due to the subjective nature of sound quality perception [146], [148], [149]. The inability of the conventional psychoacoustic noise metrics to differentiate all noises adds to the challenge [147] Ricardo used ASD to generate an augmented interior sound for an electric vehicle [149].…”

A literature review [2000–2022] on vehicle acoustics: Investigations on perceptual parameters of interior soundscapes in electrified vehicles

“…Though the ICEV was perceived as more dynamic (and less pleasant), the mere addition of ICEVresembling noise shares to the EVattempting to improve the dynamic character or to mask unpleasant noise shares with a synthetic admixed soundworsened the pleasantness and preference ratings, leading to the conclusion to consider sound design needs for each vehicle type individually (Govindswamy & Eisele, 2011). Gwak et al (2014a) modified sound samples of real EV measurements by adding subharmonics to the existing highfrequency components, which otherwise were perceived as annoying and reduced the dynamic impression of the vehicle. They had N = 27 participants evaluate the sound samples regarding preference and on a semantic differential.…”

“…They had N = 27 participants evaluate the sound samples regarding preference and on a semantic differential. The proposed sound modification method by Gwak et al (2014a) proved to be effective in enhancing the perception of the vehicles' interior soundscape: the level, number of tones, and frequency should be chosen carefully and to create a more dynamic sound impression, the tones should be under 600 Hz. Moreover, different customer groups seemed to have different preferences regarding EV sound enhancement strategies (Gwak et al, 2014a).…”

“…The proposed sound modification method by Gwak et al (2014a) proved to be effective in enhancing the perception of the vehicles' interior soundscape: the level, number of tones, and frequency should be chosen carefully and to create a more dynamic sound impression, the tones should be under 600 Hz. Moreover, different customer groups seemed to have different preferences regarding EV sound enhancement strategies (Gwak et al, 2014a). In another study, Gwak et al (2014b) tested two different sound modification approaches against each other and had 3 Please note that these findings are conducted from the article's English abstract only, whereas the article of Lee et al (2016) itself was written in Korean and not available to us in English language in an authorized version.…”