The most common car sensors used in cars are acoustic sensors measuring distance, designed for warning systems, backup and auxiliary parking systems. Acoustic distance sensors usually cost less than similar radar sensors and they are more accurate for detecting objects at a short distance.
Acoustic waves reflected from the object
Acoustic distance sensors work, transmitting the sound signal (sound) and “listening” to the reflected signal. The delay associated with the reception of the reflected signal can be compared with the distance of the reflective object. Acoustic sensors generate a signal, moving the diaphragm quickly back and forward, displacing the air around the diaphragm, creating an acoustic wave.
Acestic sensor diaphragm deflection
Acoustic distance sensors, as a rule, work at ultrasound frequencies (40 – 250 kHz). Ultrasonic sensors very well recognize objects that are relatively large compared to the wavelength of ultrasound (~ 1 cm). Ultrasound signals are distributed in the air, so that acoustic sensors cannot be reliable in situations when the air moves at high speed if the air flow cannot be measured and compensated. Acoustic sensors also have difficulties with the implementation of a reliable measurement in an acoustic noisy environment.
Manufacturers of acoustic sensors of distance: Balluff, Bestar, Bosch, Di-Soric, Longsun, Maxbotix, Microsonic, Migatron, Mitsubishi Electric, Murata, Pepperl+Fuchkwell Automation, Sandtron, S. Enix, Senscomp, Sick, Wenglor