[Must-read] Analysis of camera-based rear lateral cross warning sound system among Tesla 2025.2 software updates
Tesla has succeeded in implementing a rear-facing cross-warning system with only a camera-based (Tesla Vision) without ultrasonic sensors and radars. When reverse gears are inserted, the vehicle’s AI analyzes camera data in real time to detect vehicles or pedestrians approaching from the rear-facing side, and plays a warning sound in that direction.
- Camera-Based Rear-Lateral Cross-Sensing Principle
Tesla uses multiple cameras that monitor the vehicle’s surroundings to estimate the object’s motion and location.
Rear camera: detect pedestrians, vehicles and obstacles behind the vehicle
Left and right rear camera (B-Pillar Cameras): Vehicle approaching from the rear side
① Camera-based object tracking
Image analysis based on deep learning: Tesla Vision’s neural network estimates the speed, distance, and direction of progression of objects in real time
Optical Flow Analysis: Calculate the motion vector of an object in a continuous image frame to determine its approach
Collision Prediction: Detect danger by predicting whether the object intersects the vehicle’s travel path
② Rear lateral cross warning tone trigger condition
Vehicle is in reverse gear (R) state
Objects approaching above a certain speed will be detected by the rear camera or the B-pillar camera
The object is likely to collide with the vehicle within a certain distance
- Implementation of a directional warning sound (Spatial Audio)
It is important to not just sound the alarm, but to hear it only in that direction, depending on the direction the object is approaching.
① Analysis of speaker arrangement in the vehicle
Based on the image above, the Tesla Model 3/Y’s audio system has multiple speakers placed inside the vehicle. Specifically, the speakers that can effectively deliver the rear side warning sound include.
Rear Door Mid-Range
Rear Hatch Speakers (Rear Hatch)
Subwooper
Centre Speaker (contributes to three-dimensional sound production)
Dashboard Speakers (Dash Mid-Range) and Tweeters (forward warning tone assistance)
② Utilize stereo and surround sound
Tesla utilizes Digital Signal Processing (DSP) to deploy warning sounds in three dimensions.
When the object approaches from the left rear side → left rear door speaker + rear hatch speaker outputs sound
When the object approaches from the right rear side → Right rear door speaker + rear hatch speaker outputs sound
Object approaches from the center of the rear → utilizes the rear subwoofer and center speaker
Emergency (high risk of collision) → All rear speakers amplify warning tones
③ Utilize Spatial Sound
Tesla’s Audio System May Apply Advanced Surround Sound Technology
Adjust the volume, frequency, and echo effect (Echo) of the warning sound to provide clearer direction