Electric Vehicle NVH Development
Over recent years the automotive industry has seen a seismic shift away from the internal combustion engine towards electric motors. Be it as part of an IC / electric motor hybrid or a fully electric powertrain, and whether powered by batteries or hydrogen fuel cells, electric motor powered vehicles are becoming the new norm.

Whilst many perceive electric motor vehicles to be completely silent, in truth the Electric Drive Unit (EDU) emits several different but no less important sound signatures, which still have to be carefully considered if a good level of overall vehicle refinement is to be achieved. Whether these are the electromagnetic noises created by the motor and its inverter drive,  or mechanical noises from the integral reduction gearbox or ancillaries, a new group of sound sources is emerging.

The lack of previously dominant combustion engine noises also means that remaining noise sources such as road, wind, and ancillary noises become all the more noticeable within the vehicle interior.

AVA Consulting have been working hard to analyse and understand these new sound sources, and learning how to reduce, tune, and balance them with the existing vehicle sounds.

Electric Vehicle NVH Assessment

  • Track / Road Testing are used to evaluate the subjective and objective sound levels and sound quality inside the vehicle cabin.
  • A 2WD/4WD vehicle dynamometer is used to more precisely measure motor whine and ancillary system noise under driving conditions, without the masking noise contributions of tyre and wind noise.
  • Analysis techniques include Motor Whine Order Analysis, and Source Balance Assessment - (Drive Unit, Road, and Aero Noise)

Electric Drive Unit Integration

As the nature of the significant noise sources of an electric motor vehicle changes, so must the methods of powertrain integration.
  • Highly tonal noises present over a wide frequency range
  • Reduced masking noise, absence of engine combustion 
  • Quieter but less 'pleasant' more 'annoying' noises
To address these at a vehicle level requires:-
  • Improved mount isolation
  • Improved vehicle structural dynamics
  • Airborne noise treatment tuning

Road Tyre & Aeroacoustic Noise

The removal of the IC engine sounds not only reduces the masking of ancillaries, it also has a similar effect on existing noise contributors such as road and aeroacoustic noise, making them sound louder and more annoying. This leads towards a renewed emphasis on road and aeroacoustic noise improvements including:-
  • Door and Window Seals
  • Mirrors and Roof Detail Design
  • Tyre Design 
  • Tyre Noise Absorbers 

Electric Vehicle Sound Quality

Once EV powertrain, road, and aeroacoustic sources have been reduced, and ideally balanced, EV's can sometimes sound somewhat 'bland', and lacking in the noise feedback for speed and load that we take for granted from IC engines. This has lead some manufacturers to look at ways of enhancing the sound quality of electric vehicle noise.
  • Electronic Sound Feedback Devices
    • Loudspeakers
    • Panel Shakers
    • Active 'Exhaust' Loudspeakers
  • Mechanical Sound Enhancement
The principal difficulty is to find a way to enhance the vehicle sound whilst retaining authenticity.
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