What are the best ways to reduce NVH in electric and hybrid vehicles?

1 Electric motor noise

One of the main sources of NVH in electric and hybrid vehicles is the electric motor, which generates high-frequency noise and electromagnetic interference. The electric motor noise can be reduced by using proper insulation, shielding, damping and isolation materials, as well as by optimizing the motor geometry, control and cooling systems. Additionally, some electric and hybrid vehicles use active noise cancellation or sound masking techniques to counteract or mask the electric motor noise with synthetic sounds.

2 Gearbox and driveline noise

Another source of NVH in electric and hybrid vehicles is the gearbox and driveline, which transmit the torque from the electric motor to the wheels. The gearbox and driveline noise can be reduced by using low-noise gears, bearings, lubricants and couplings, as well as by minimizing the backlash, misalignment and imbalance of the components. Furthermore, some electric and hybrid vehicles use a single-speed or continuously variable transmission (CVT) to avoid gear shifts and reduce the speed variations of the driveline.

4 Cabin noise

A fourth source of NVH in electric and hybrid vehicles is the cabin noise, which is the result of the transmission and reflection of the external noise sources into the interior space of the vehicle. The cabin noise can be reduced by using sound-absorbing and sound-blocking materials, such as foams, carpets, fabrics and plastics, as well as by enhancing the sealing and fitment of the doors, windows and panels. Additionally, some electric and hybrid vehicles use active sound design or sound enhancement techniques to create or modify the sound environment inside the cabin.

5 Battery noise

A fifth source of NVH in electric and hybrid vehicles is the battery noise, which is generated by the thermal expansion and contraction of the battery cells and modules, as well as by the cooling fans and pumps. The battery noise can be reduced by using thermal management and vibration isolation systems, as well as by optimizing the battery layout, packaging and mounting. Furthermore, some electric and hybrid vehicles use passive or active cooling methods to regulate the battery temperature and reduce the fan or pump noise.

6 Structural vibration

A sixth source of NVH in electric and hybrid vehicles is the structural vibration, which is induced by the dynamic forces and moments of the electric motor, gearbox, driveline, tires, road and battery. The structural vibration can be reduced by using lightweight and stiff materials, such as aluminum, carbon fiber and composites, as well as by applying modal analysis and optimization techniques. Moreover, some electric and hybrid vehicles use active vibration control or damping devices to counteract or dissipate the structural vibration.