Surely at some point during a road trip you have experienced, without knowing it, what is known as the helicopter effect. When the heat is on, when we don’t want to fall asleep or simply out of pure mania, we drivers tend to roll down our door windows. This produces a very annoying noise for our eardrums, similar to that produced by the blades of a helicopter, which can stun us greatly.
The noisy helicopter effect occurs due to the encounter of air trying to enter the vehicle with which it is trying to leave. That is why, when you open the passenger window, an outlet is created for air, which creates a draft and causes the noise to be attenuated or disappear.
The truth is that the helicopter effect is an old concern of automobile manufacturers. In the middle of the last century, when cars lacked air conditioning and the windows were cranked, some, like Alfa Romeo, implemented some solutions such as slightly opening the lower part of the rear window. These designs favored the release of outside air and interior ventilation of the car without the need to open the windows.
This problem has returned to the present day due to the rise of the electric car. Driving with the heating or air conditioning on can sometimes overload the batteries and affect the overall performance of the vehicle. Paradoxically, the helicopter effect affects drivers more the higher the range of their car.
The design of modern cars has adopted significant improvements in aerodynamics and cabin pressurization compared to older cars, which also encourages the helicopter effect to occur. In this way, the outside air exerts greater pressure on the vehicle and tries to sneak in through any crack. Meanwhile, indoor air also has a hard time finding a place to escape. The helicopter effect tends to occur in contemporary electric cars, vehicles characterized by excellent aerodynamics and powerful insulation.
Manufacturers like Tesla are working on solutions to tackle the helicopter effect. One of them would consist of emulating the slit that opened at the bottom of the rear window of cars from the 60s and 70s to ventilate the cabin. Another feasible solution is solar roofs, since they enable the circulation of outside and inside air without the need to roll down the windows.