During the process of development of electric heavy vehicles the focus on sound quality have become much more important. Shifting the internal combustion engine to electric propulsion, has not only decreased the sound levels. The sonic character is now more tonal and needs other evaluation routines and new target settings. 

The purpose of this work is to define applicable methods and target values to, in the long term, secure good sound quality and safe vehicles. To accomplish this mission several sub-questions needs to be investigated such as perception of prominence and loudness of complex tones, underlying aspects for evaluation of sounds as well as behavioural effects and comfort during driving.

In the present work, listening tests were made to study how the number of tone components and frequency intervals between the components affect the perception of the perceived loudness of complex tones. The listening tests revealed that there is a linear relationship between perceived loudness and increasing number of harmonics of a complex tone with amplitudes of the partials decreasing 6 dB per octave.

To study underlying aspects for sound assessments, qualitative data from a previously performed listening test on a first-generation battery electric truck was studied. The method of thematic analysis was used to derive information about what decided if a sound was evaluated as positive or negative. Various aspects have an impact on the outcome.

Interrelation between tonal components needs to be considered when setting targets on sounds with complex tonal content to give valid estimations of loudness and prominence. Subjective evaluation of dynamic driving operations depends of several different factors. These are connected to the individual such as listening and contextual experience, individual values and preferences, hearing function, relation between feedback and input as well as acoustical features. Informative sounds with close connection to load and speed are desirable.