Ultrasonic Sensor
An ultrasonic sensor measures short-range distance by transmitting a high-frequency sound pulse and timing the returning echo.
What it means in a vehicle
Cars commonly place several ultrasonic sensors across the bumpers to monitor the area close to the body. Their distance estimates support parking sensor, automated parking, maneuver warnings, and some low-speed braking functions.
The measurement is a reflected sound signal, not an image. Target angle, shape, height, and material affect the echo, so a thin post, soft surface, low curb, or object outside the acoustic beam can be difficult to detect. Dirt, ice, bumper damage, or an unsuitable paint repair can also disturb the acoustic path.
Ultrasonic sensors are therefore useful near-field aids, but they do not classify a whole scene or prove that every nearby obstacle is clear. Cameras and other sensors may add different evidence.
For the detailed ranging principle, installation, limitations, and camera-based alternatives, see Ultrasonic Sensors.