What should an electric vehicle sound like?

By James K. Thompson, Ph D, PE, INCE Fellow, INCE Bd Cert, JKT Enterprises

You may not have asked this question, but auto manufacturers have spent hundreds of millions of dollars trying to find the right answer.  

Maybe this seems like a dumb question to some. You may think an electric vehicle (EV) should sound like whatever it sounds like. However, this has never been the case even with internal combustion engines (ICE), original equipment manufacturers (OEM) spend hundreds of millions of dollars shaping the interior sound. They use active noise control (ANC) and sophisticated seals, absorption materials, and barriers to control interior noise. For the last few decades, the OEMs have gone further by adding noise either artificially or channeled from the engine compartment or the exhaust to shape the interior noise. This is all done to provide a “positive” experience for the customer. It may be that the OEM feels the customer wants more audio feedback when he or she stomps on the accelerator. The goal may be to have the driver experience more engine sound while better isolating the other passengers.  

So, the question of how an electric vehicle should sound is important to OEMs. Some OEMs have worked with creative artists to develop an entire artificial sound spectrum for their electric vehicles. This “sound” is delivered to the interior of the vehicle and masks sounds coming for the electric drive train, wind, and road noise.  

Some of you are asking why this is necessary. The removal of the ICE powerplant and transmission from a vehicle removes many of the “typical” sources of noise we associate with vehicle operation. Replacing that with an electric drivetrain with completely different characteristic sounds and vibrations further complicates the situation. In some sense, it places the operator and occupants in an unfamiliar acoustic environment. Components of tire and wind noise that were previously masked by ICE sound become new and strange. In addition, the electric drive train adds new and different noises into the mix. Quiet components that were never heard before become noise issues.  

There is a famous story of the lady who brought her new high-end electric vehicle into the dealership for repair stating that the fan would not shut off. The dealer checked the vehicle HVAC system, and it was working properly. The vehicle was returned to the lady and as soon as she got in, she told the service rep that the noise was still there. After some investigation, it was discovered that the sound was coming from a cooling fan in the navigation system. This sound was inaudible in the ICE engine vehicle with the engine running but was clearly apparent in the EV version. In fact, there were papers at this year’s NOISE-CON conference on new work to further quiet computer-based systems in EVs due to this sort of issue.  

I will confess, before leading you on any further, I do not know how an EV should sound. I am not sure anyone has a definitive answer. There are a lot of solutions in the marketplace and how it will evolve is anyone’s guess. The issues wrapped up in the question are quite complex. Some OEMs have a brand sound or acoustic characteristic they want to preserve. Others see an opportunity to have a unique “vehicle of the future” sound characteristic associated with their EVs. Day to day, engineering teams are scrambling to control or mask new and unique sounds associated with the EV that were not apparent before.  

When I say the situation is evolving, there are a lot of different approaches. More than one company now sells a kit to add to your EV to add exterior noise, so that your EV sounds like an ICE sports car as it drives down the street. As you might expect, the sounds levels from this kit far exceed the sound levels from the vehicle they are trying to emulate. The moto here seems to be the louder the better. I doubt the neighbors or those in traffic would agree.  

I recently talked with the owner of an EV who was extolling the virtues of the interior sound in their vehicle. Their description was “it sounds just like a jet airplane taking off.” Clearly it did not really emulate these sonic characteristics and certainly not the sound levels of a jet during takeoff. However, this is the impression this owner had, and it was quite pleasing in his opinion. Knowing that this was a vehicle where the engineering team had done a lot of work to create an artificial sound to give the occupants an impression of acceleration and “future tech,” I guess this was a success story.  

I am interested to know how you think an EV should sound. If you have an EV, are you pleased, annoyed, or oblivious to all the work done to provide an artificial sonic environment for your driving pleasure.