Electric vehicles need to emit sound. Here’s how that happens.

Electric vehicles are a blank canvas. At least sonically.

Without engine noises and with fewer moving parts, battery-powered vehicles make about as much noise as your cellphone. It’s a much quieter experience than we’re used to, after years of vrooming, revving, and other clanging coming from under the hood. The nearly silent experience has prompted new regulations in the U.S. and Europe, requiring carmakers to build in warning noises to alert pedestrians to oncoming hybrid and all-electric vehicles. It also means car companies are experimenting with the sound experience in an entirely new way.

BMW tapped Hollywood composer Hans Zimmer to “think about the holistic and immersive sound experience for our drivers,” a BMW executive explained at Zimmer’s Santa Monica, CA, recording studio ahead of the Los Angeles Auto Show this week. 

Starting in 2020, BMW’s electric vehicles will feature an exclusive start/stop sound created by Zimmer, the official BMW curator for electric sounds, and BMW sound designer Renzo Vitale. Because there’s no sound cue from a combustion engine, it’s intended to let the driver know the car is ready to go, or that the car is off. 

I sat near Zimmer as a room of reporters listened to the new sound (inspired by a sculpture) that’s a blend of female voices coming together. Take a listen: 

Zimmer described the electric car as a space with “unlimited potential” where “you can do anything you want.” He joked about adding “the most delicious Beatles chord” to greet you when you first enter the car, but for now the car stays silent until you turn it on. The start/stop sound is the literal start of the Zimmer-BMW partnership. He plans to develop more sounds for EVs, like a sound for when the car is moving fast.

Toyota Uruguay (known an AYAX Toyota in South America) is taking a different approach to EV sounds: The company is thinking about noise pollution and how sounds affect nature.

“We should be taking care of what kinds of sounds we’re adding to the world,” Juan Ciapessoni, co-founder of Uruguayan marketing company The Electric Factory, said in a recent phone call about his company’s collaboration with an independent Toyota manufacturer based out of Uruguay.

Looking at studies about noise affecting plant growth and animal migration, Toyota came up with an electric and hybrid sound for pedestrian warning that promotes plant growth. It’s part of the Hy Project, which claims to have researched and tested frequencies that don’t disturb animal communication for hunting, mating, and just living. 

Caipessoni described the car sound as insect-like. But the engineering team “didn’t want it to [sound] like science-fiction,” so it created a more “healing sound.” The sound designers worked within the findings of various studies about the effects of noise and plant stimulation and tried to find a sound that hit the right frequencies from the research, but didn’t sound too eerie or otherworldly. They also had to make sure the sounds didn’t interfere with any of the car computer systems and other sounds, like those for a seatbelt warning or open door.

The sound is already in some car-shares in Uruguay, Alejandro Curcio, president of AYAX Toyota, said, and eventually it could be used for Toyota hybrids throughout Latin America. The Uruguay team wants the nature-friendly noise to be associated with Toyota everywhere, including in the bigger U.S. and Japanese markets.

Ford’s 2020 hybrid Ford Escape and Explorer cars coming out next year will alert pedestrians with a Ford-designed sound. Working with groups like Leader Dogs for the Blind, engineers built a sound that has a similar frequency to an internal-combustion engine for when the car is moving below 19 mph. The blind community was integral in setting new regulations for better sound features on hybrid and all-electric vehicles. Here’s the alert with its modulating frequencies.

Ford also worked with music and movie sound production teams to develop a sound people will hear when a vehicle is moving or nearby. 

In a throwback move, the new all-electric Porsche Taycan offers a “Porsche Electric Sport Sound” that “enhances the vehicle’s own sound and makes it sound even more emotional — both outside and inside the vehicle,” the website says. The sound is hidden under the “Performance” section of the Porsche Taycan website and comes at you in a big whoosh. It’s an extra $500 for the sound feature on the $100,000 (that’s base price) electric vehicle. Sounds … good?