Acoustic pulse recognition( APR) is one of several methods used in touchscreens to determine the position on the screen. The APR method is a variant of Surface Acoustic Wave( SAW), but works without its own transmitter.
The APR technique determines the location where the touchscreen is touched based on the vibration that propagates across the screen. The vibrations are detected by piezoelectric sensors located in the four corners of the screen. Based on the vibration energy recorded by the four sensors, the touched position is determined by comparing it to a table of values. In this respect, APR touchscreens differ from other methods in which the position is calculated by amplitude damping or sound shifts. A prerequisite for position determination, however, is that the touchscreen is touched. Otherwise, no vibration is triggered.
Touchscreens with acoustic pulse detection consist of a glass panel. They are therefore robust and scratch-resistant and show the underlying display clearly.