EVs are by nature far quieter, so more thought needs to go into the sounds they make when doing routine things. Rivian saw this as an opportunity to reinforce the outdoorsy branding of its R1T electric pickup truck and R1S electric SUV, choosing sounds inspired by nature.

Even without an internal-combustion engine, cars make lots of sounds. From turn signals to the pedestrian warning sounds now mandatory on EVs and hybrids, each needs to be purposefully chosen. Rivian worked with sound design firm Audio UX to do this, whittling down about 900 sounds to around 40 that actually made it into production vehicles, the company said.

Among the winners was a pedestrian warning sound based on wind and water, a wood-like thump for the turn signals, and a double chirp vehicle-lock sound based on the call of a mountain bluebird.

Rivian R1T sound test

Rivian R1T sound test

The frequency of bird chirps falls within the most sensitive hearing range of the human ear, making them a good fit for car notification sounds, Rivian noted. Higher-frequency chirps also aid directional location, according to the automaker, while still blending in to the natural soundscape, unlike the typical beep of a car horn.

The R1T and R1S don't simply play recorded bird calls, though. Sound engineers recorded birds in Yellowstone National Park, then isolated one part, sped it up, and increased the pitch.

Engineers also aimed to group certain types of sounds based on function. Navigation alerts and related sounds are largely animal-inspired, while warning sounds use a dissonant chord with a rapidly repeating single note at the end, which Rivian claims cuts through other noises. 

Other automakers have tried to put a unique signature on EV alert sounds. The team behind the sounds in the Ford Mustang Mach-E didn't want something that sounded like the digital sound of a combustion engine, aiming for something both new and familiar in keeping with the electrification of the popular Mustang nameplate.

Nissan has looked to a "Canto" sound for its current and future EVs that's, in the automaker's phrasing, "energizing" and "confident." Dodge, on the other hand, is looking to a chambered, "bone shaking" sound system to make a lot of electric noise in its Charger Daytona SRT muscle-car concept.

Many automakers have found a way to synchronize the themes of its vehicle sounds with those that the EVs need to make at low speed to alert pedestrians, per federal regulations. A recent petition seeks to make that rule retroactive to about 9 million older hybrids and EVs, too.