You are walking across a parking lot, and a car suddenly appears beside you.

You did not hear it coming.

That moment is becoming more common as electric vehicles appear on the road. Electric motors produce very little mechanical noise. At low speeds, the loudest sound often comes from the tires touching the pavement.

That quietness may sound like progress.

But it also created a problem.

Pedestrians, cyclists, and particularly visually impaired people often rely on sound to sense traffic. A nearly silent vehicle approaching from behind can be difficult to notice, especially in busy urban environments.

Because of this, regulators in many countries now require electric vehicles to produce sound at low speeds.

The system is called an Acoustic Vehicle Alerting System, or AVAS. When the vehicle moves at roughly 20 to 30 kilometers per hour or below, the car emits a synthetic tone so people nearby can hear that it is moving.

Engineers had to design noise again.

This requirement created a new specialty within the auto industry. Car companies now employ acoustic engineers who focus on how a vehicle sounds.

Their work includes warning tones, cabin alerts, the external sounds electric vehicles make at low speeds, and the sound cues drivers hear during acceleration.

Some manufacturers take the idea further.

BMW worked with film composer Hans Zimmer to develop sound signatures for its electric models. Porsche offers an optional Electric Sport Sound system for the Taycan.

Hyundai created simulated gear shifts and engine sounds for the high-performance Ioniq 5 N.

Dodge even developed a system called the Fratzonic Chambered Exhaust for its electric Charger to produce an exhaust-like sound through external speakers.

At first, the idea may seem strange. Why add noise to a machine designed to be quiet?

Sound provides feedback to the driver.

Drivers often judge speed and acceleration through sound. Engine noise rises when the car accelerates and falls when the driver eases off the throttle. Remove that cue, and the experience can feel unfamiliar.

Even gasoline cars receive careful sound tuning.

Engineers adjust intake noise, exhaust resonance (or how sound waves travel through the exhaust pipes), cabin insulation, and the sound that reaches the cabin to control what the driver hears.

Some vehicles even send amplified engine sound through the cabin speakers.

In other words, the sound of a car has never been entirely accidental.

Sound also plays a role in everyday traffic.