Quietest Cars: Do Electric Cars Make Any Sound?

Electric vehicles (EVs) are famously quiet. Unlike traditional combustion engines, electric motors don't require mechanical valves, gears, or fans.

While idling, an EV motor hums quietly. When moving, passengers can hear the tires and wind.

This can be a boon in urban environments, where road traffic is the main contributor to noise pollution. But it can also be a drawback, as quieter cars can pose dangers to children or the visually impaired.

Vehicle Noise Pollution

Vehicles are sources of both air and noise pollution. Today, 55% of the world's population lives in cities. This density increases the impact of vehicular pollution on residents.

Additionally, noise pollution is one of the greatest threats to wildlife.

Traffic noise suppresses frogs' immune systems. It decreases the ability of birds to communicate with each other and to detect predator threats. And it reduces terrestrial wildlife's ability to forage, care for their young, and reproduce.

During coronavirus lockdowns in 2020, noise levels in urban environments dropped 35% to 68%. This contributed to a temporary wildlife rebound. With EVs, those reductions could be permanent.

Reduced Vehicle Noise With EVs

City planners have made various efforts to mitigate urban noise pollution through better design. But quieter vehicles present a cleaner, easier solution.

At 10 mph, internal combustion engine vehicles emit roughly 55 decibels. This is already more than the World Health Organization's recommendation that noise levels at night remain below 40 decibels.

At speeds up to 20 mph, EVs (and hybrids driven in electric mode) are far quieter than vehicles with internal combustion engines. An electric motor is nearly silent, meaning “rolling noise” from tires and wind are the main source of EV sound.

When moving at higher speeds, the difference between a gas-powered car and EV noise production shrinks. Tire and wind noise represent a greater percentage of total traffic noise at speed, and these are consistent regardless of the motor.

In the pursuit of energy efficiency to increase EV driving range, many EV manufacturers emphasize aerodynamics to reduce the drag coefficient. This reduces wind noise too, so that even at higher speeds, EVs can be quieter than gas-powered cars.

Quiet EVs Can Confuse Drivers

The absence of engine noise (and vibration) has led to complaints about road and wind noise among EV drivers. But auto engineers are actively refining EV designs to limit internal noises.

In an EV, drivers can hear subtler noises that are drowned out by gas-powered engines. The magnets in an electric motor can also emit high-frequency noises, which is noticeable at low speeds.

One study predicts that acoustic and thermal insulation materials for EVs will grow by 21% annually over the next decade. The challenge, however, is the added weight.

In an internal combustion engine vehicle, sound-deadening materials are added without great impact on gas mileage. Adding extra weight to an EV, however, reduces the battery range. Finding the right balance between weight and noise-canceling is key for the future of EVs.

Quiet EVs and Pedestrians

Quiet EVs have prompted concerns about pedestrian safety. Since they are so quiet, it's harder for children, animals, or the visually impaired to recognize when an EV is nearby.

Since 2019, the U.S. National Highway Traffic Safety Administration (NHTSA) has required new EVs to automatically make noise when they are traveling slower than 18.6 miles per hour “to ensure that blind, visually impaired, and other pedestrians are able to detect and recognize nearby hybrid and electric vehicles.” Beyond 18.6 mph, road noise emitted by EVs is nearly the same as that of gasoline cars.

In Europe and Australia, electric vehicles must be equipped with an Acoustic Vehicle Alert System (AVAS) that emits noise at speeds lower than 20 kilometers (12 miles) per hour. The AVAS noise in some EVs is external only, so those inside the car may not even hear it.

The threat to pedestrian safety doesn't just affect the blind or visually impaired, however, since inattentive sighted walkers texting in crosswalks may fail to look up from their phones without noticeable vehicle noise. While data is limited, studies suggest a link between pedestrians being distracted by mobile phone use while crossing streets and a rise in pedestrian-vehicle collisions.

Artificial Noise

Creating artificial noises to conform to AVAS requirements leaves car manufacturers with the opportunity to create brand sound signatures. BMW, for example, is working with a Hollywood composer to create a specific sound for its EVs. Volvo, by contrast, has opted to merely increase the expected road noise of a vehicle rather than create its own custom sound. While the sounds need to be within volume standards set by the governing regulations, what could emerge is a medley of different sounds from different vehicle makes on the road. Whether that's a good thing or a bad thing remains to be seen.