SOUND ENGINEERING FOR ELECTRIC AND HYBRID VEHICLES: Procedures to create appropriate sound for electric and hybrid vehicles

Stephan Brandl; Bernhard Graf

doi:10.4271/2011-39-7228

Importance of electric and hybrid vehicles steeply increased in the last few years. Especially topics like CO2 reduction and local zero emissions are forcing companies to focus on electrification. While main technical problems seem to be solvable from a technical point of view, commercial and security topics are gaining more importance.

For full electric vehicles the driving range is limited by the capacity of available batteries. As those batteries are one of the most heavy and expensive parts of these vehicles, reduction of battery size is a big topic in vehicle development. To increase a vehicle's driving range without increasing battery size some range extending backup system has to be available. Such a Range Extender should be a small system combining combustion engine and electric generator to produce the required electricity for charging the batteries whenever required.

Since the acoustic excitation of an electric engine driving the vehicle is very low compared to an internal combustion (IC) engine, sound characteristics of electric and hybrid cars differ considerably from conventional passenger cars. Requirements, especially for a combustion engine as part of a Range Extender are therefore very demanding as overall sound pressure level for electrical vehicles is much lower in many driving conditions compared to conventional cars. Therefore exterior vehicle noise and passenger comfort require an extensive acoustic tuning of the Range Extender unit.

As electric vehicles are mainly targeted to serve inner city traffic they are mainly operated at slow driving speeds. Due to the low overall exterior sound pressure level other traffic participants (e.g. pedestrians and cyclists) tend towards overseeing electrically driven vehicles. Therefore strategies for the completely new field of exterior sound engineering have to be developed.

This paper presents the NVH (noise, vibration & harshness) development work of a range extender within the AVL approach of an electrically driven passenger car. The work starts with acoustic front loading in the concept phase and with NVH simulation in the design stage and is continued with intensive NVH development during integration into the electric vehicle. Additionally new strategies and ideas for interior and exterior sound design are discussed in this document.

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SOUND ENGINEERING FOR ELECTRIC AND HYBRID VEHICLES: Procedures to create appropriate sound for electric and hybrid vehicles 2011-39-7228

SAE MOBILUS