The psychoacoustics of electric vehicle signature sound

Swart, Daniel Johannes (2018-03)

Thesis (PhD)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: The automotive industry is currently exploring the global sound sphere to identify a pleasant, safe and unique electric vehicle signature sound. Drive-train acoustics contribute to the performance benchmark of vehicles in the marketplace. Electric vehicle sound signatures differ vastly from those of internal combustion engines. Questions arise as to how these signature sounds relate to consumer experiences, and how the positive attributes of these sounds can be extracted and enhanced. The presented work aimed to investigate the objectively and subjectively evaluated attributes of electric vehicle signature sound, and the associated consumer satisfaction. A subjective evaluation procedure for the classification of the noise produced by electric vehicles was adapted from existing methodologies for internal combustions engines. Itwas found that ‘Calm’, ‘Deep’, ‘Rumbling’,‘Creative’ and ‘Futuristic’ semantics should be added to existing tests to typically describe electric vehicle sound character. The sound signatures of six standard production electric vehicles and one hybrid electric vehicle were benchmarked through constant speed andWide Open Throttle drives. Time and frequency domain analyses were used to compare the different vehicles, and results revealed that electric vehicles contain substantial sound energy in the upper frequency bands due to the tonal components. Lower sound pressure levels were achieved in a multi-stage gearbox, with regards to the high frequency content associated with electric motors. High Prominence Ratio levels, in excess of 10 dB,were found for electric vehicles and current literature points to diminished consumer satisfaction as a result. Furthermore, standard production electric vehicle sound signatures were evaluated against enhanced sound stimuli, based on subjective semantics and objective metrics, to determine the dimensions of electric vehicle sound quality that can lead to improved consumer satisfaction. The methodologywas to undertake two independent subjective evaluations, performed by a jury of 32 and 52 members respectively, to determine the perceived electric vehicle sound experience. Results showed that Sharpness is fundamental to governing the electric vehicle sound experience. Secondly, the underlying dimensions of electric vehicle sound quality are sparsely described in literature and was therefore investigated. A factor analysis found that additional to the dimensions of refinement and powerfulness of internal combustion vehicle sound, electric vehicles also have a third dimension associated with a ‘Futuristic’ factor. Lastly, a consumer satisfaction model was proposed through multiple linear regression and the 95th percentile Sharpness value. The model yielded promising results for both interior and motorbay sound signatures and is proposed as a means of gauging consumer satisfaction for electric vehicle sound quality. The complexity of electric vehicle sound character was discussed and recommendations were offered with respect to the design considerations of future electric vehicle sound signatures. A holistic approach regarding both subjective and objective evaluation methods is recommended for future electric vehicle research, in order to fully understand the attributes that govern electric vehicle sound quality.

AFRIKAANSE OPSOMMING: Die voertuig industrie is huidiglik op soek na ’n unieke elektriese voertuigklank binne die globale klankruimte, wat uniek is en ‘n gevoel van genot en veiligheid oordra. Die akoestiek van die aandryfstelsel dra by tot die prestasie-maatstaf van voertuie binne die mark. Elektriese voertuig handelsmerk-klank verskil baie van dié van binnebrandenjins. Vrae ontstaan oor hoe hierdie handelsmerk-klanke verband hou met verbruikerservarings, en hoe die positiewe eienskappe van hierdie klanke onthul en verbeter kan word. Die uiteengesette werk het ten doel om die objektiewe en subjektiewe geëvalueerde eienskappe van elektriese voertuig handelsmerk-klank, en die gepaardgaande verbruikersbevrediging, te ondersoek. ‘n Subjektiewe evalueringsprosedure vir die klassifikasie van die geraas wat deur elektriese voertuie weergegee word, is aangepas uit bestaande metodologieë vir binnebrandenjins. Daar is bevind dat die ‘Rustige’, ‘Diep ’, ‘Dreunende’, ‘Kreatiewe’ en‘ Futuristiese’ semantiek by bestaande toetse gevoeg moet word omdie tipiese elektriese voertuigklankkarakter te beskryf. Die handelsmerk-klank van ses standaard produksie elektriese voertuie en een hibriede elektriese voertuig is deur middel van ritte teen konstante spoed en volle versnelling getoets. Tyd en frekwensie domein analise is gebruik omdie verskillende voertuie te evalueer. Bevindings het getoon dat elektriese voertuie merkwaardige klankenergie in die hoë frekwensie bande vertoon, as gevolg van die tonale klankkomponente. Laer klankpeilvlakke is bevind in die veelvuldige ratkasstelsel met inaggenome die hoë frekwensie geraas wat met elektriese motors geassosieër word. Hoë vlakke (È10 dB) van prominente tone is ondervind op elektriese voertuie en bestaande literatuur koppel dit aan verlaagde verbruiker-tevredenheid. Voorts is standaard produksie handelsmerk-klanke geëvalueer teenoor verbeterde klank stimulasies, gebaseer op subjektiewe semantiek en objektiewe metrieke, om die dimensies van die elektriese voertuigklankgehalte te bepaal, wat tot beter verbruikersbevrediging kan lei. Die metodologie was om twee onafhanklike, subjektiewe evaluerings te onderneem wat deur ’n paneel van 32 en 52 lede respektiewelik onderneem is, om die waargenome elektriese voertuigklankervaring te bepaal. Resultate het getoon dat Skerpheid ’n fundamentele rol speel in die elektriese voertuig klankervaring. Tweedens word die onderliggende dimensies van die klankgehalte van elektriese voertuie ondersoek, aangesien dit weinig in die literatuur beskryf word. ‘n Faktor-analise het bevind dat die ‘Futuristiese’ semantiek dimensie, aangevul moet word, by die huidige ‘kragtige’ en ‘gesuiwerde’ semantiek, wat reeds vir binnebrandenjin voertuie bestaan. Laastens is ’n verbruikersbevredigingsmodel voorgestel deur middel van meervoudige lineêre regressie en die 95ste persentasie Skerpheidswaarde. Die model het belowende resultate opgelewer vir beide kajuit- en motorkompartement handelsmerk-klank. Hierdie modelword voorgestel as ’n metodeomverbruikersbevrediging van elektriese voertuigklankgehalte te bepaal. Die kompleksiteit van die elektriese voertuigklankkarakter is bespreek en aanbevelings is voorgestel met betrekking tot die ontwerpskonsepte van toekomstige handelsmerk-klank van elektriese voertuie. ‘n Holistiese benadering rakende beide subjektiewe en objektiewe evalueringsmetodes word aanbeveel vir toekomstige elektriese voertuignavorsing, ten einde die eienskappe wat elektriese voertuigklankkwaliteit reguleer, ten volle te verstaan.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103816
This item appears in the following collections: