Electric motors are not only better for the environment, they are also quieter than combustion engines. This creates some challenges for engineers specializing in acoustics, who need to find new technologies and strategies for noise reduction in electric vehicles.
This is because as the engines are quieter, other vehicle noises are even more evident inside electric cars, such as the air conditioning compressor, the flow of air around the vehicle, the flow of air in the ventilation ducts and the contact of the tires with the asphalt.
Even the noise of the rain and the closing of the doors can become a nuisance! Reducing or improving the quality of these noises is very important to increase driving comfort and also for the safety of pedestrians and cyclists.
Therefore, engineers around the world develop various simulations and tests to control noise levels.
The noise sources
In vehicles with a combustion engine, there are noises derived from the internal components themselves, such as fuel tanks or exhaust system. These (and other) components do not exist in electric vehicles. But, on the other hand, there are now other types of noises.
For example, noise from tires in contact with the road, from the wind, or from electrical components was not relevant (or did not exist) in automobiles with a combustion engine, but interfered with the experience of driving an electric car.
Therefore, noise reduction strategies in electric vehicles include understanding what these noises are and how they are perceived inside the vehicles.
Although they are quieter, electric motors are not 100% noise-free. There are components, such as inverters and current converters. Therefore, NVH researchers need to develop strategies to make engines efficient and with low noise levels.
Electrical devices operate air conditioning, heaters, windows, among other features. All result in vibrations and influence the noise level.
Tire and road noise
Although the engine makes noise, the main discomfort that drivers and passengers can feel comes from the noise of the streets themselves. And if the car is faster, the noise increases.
The absence of other sounds and the structure of electric vehicles make this sound more evident. For example, the vehicle’s weight distribution can make street noise more evident inside the car.
To reduce these noises, it is necessary to invest in research on the technology of tires, suspensions and other components of the interior and exterior of the vehicle. The main challenge is to do this without adding cost to the final product.
It is at this point that simulations, numerical and advanced tests prove to be beneficial for projects in the EV industry. With these tools, it is possible to reduce final project costs, as results can be anticipated without the need to perform physical tests.
Noise reduction and street safety
In addition to these issues, engineers also need to be concerned about the safety of pedestrians on the streets. After all, cars that are too quiet can be worrying for pedestrians, since hearing is a very important sense when crossing a street, for example.
Therefore, automakers already carry out studies on what external noises can signal to those who are on the street, without this harming the comfort of drivers and passengers.
An interesting alternative, according to some companies in the segment, is to invest in noise cancellation systems for the interior of vehicles.
What is noise cancellation
Have you ever put on a headset that completely blocked out sound? This is noise canceling. It is a technology that blocks out noises that come from outside.
There are projects to study noise cancellation inside electric vehicles. Thus, those inside the car are not distracted by the noises emitted by “external components”, such as the engine or the tires, and pedestrians can hear the cars approaching.
In any case, there are no definitive solutions, but improvements that are made according to the needs of each project and different markets. The fact is that insulation and noise reduction are very important for the future of the growing electric vehicle industry.
Vibroacustica is specialized in NVH analysis and simulations in several areas, in addition to having expertise in compressor projects for national and international customers.