Acoustic Applications for Electric Vehicles

Measuring acoustic performance on an electric vehicle (EV) or hybrid-electric vehicle (HEV) platform introduces new challenges compared to typical internal combustion engine (ICE) platforms.

Sounds from an EV platform are often comparable to those in an ICE platform but especially the frequency range can be very different. EVs introduce new types of higher frequency noise sources, especially from the inverter, electric motor and battery charger and are also influenced by the use of lightweight damping material.

EVs introduce new types of higher frequency noise sources, especially from the inverter, electric motor and battery charger and are also influenced by the use of lightweight damping material.

Due to the absence of low-frequency engine noise in EVs to mask other noises, these new high-frequency tonal noises are often much more distinct. At high speeds, the motor e.g. will cause a howling sound, which can be very disturbing to the driver.

The general increase in high-frequency content makes it difficult to do TPA/ENR (transfer path analysis / engine noise reduction) types of measurements from the engine bay since many sound sources have limited energy already at 10 kHz. 

In an environment with high frequency content, extra care therefore has to be taken in order to measure and map the distribution of content reliably.

Inverters
Inverters emit noise related to the switching frequencies and duty cycle. Switching frequency will typically be constant in frequency whereas duty cycle will change with load. Thus, the load will change at acceleration or regeneration.

Electric motor
There are many different solutions for electric motors for EV platforms. Typically, there will be a single large motor, but there can just as well be two or four depending on purpose, performance, etc.

Charging
Since charging the battery most likely will utilize the same power electronics as at regeneration – though at a more constant rate – this may generate an unpleasant whine from the power electronics and discourage passengers from staying in the car during charging.

Lightweight damping material
As OEMs are struggling to reduce the weight in EVs, the damping in different locations may be reduced with time. Obviously, the added use of lightweight materials also influence the impact of the other noise sources.