Hello!
In the datasheet for the MOD CH-101, it states on page 10:
5.1 SENSOR MOUNTING
The MOD_CH101-03-01 is omnidirectional, allowing the sensor to detect objects over a very wide field-of-view (FoV). However,
omnidirectional response is only achieved when the sensor is mounted in a flat surface, free from reflecting edges. To achieve the best
acoustic performance, users are recommended to mount the MOD_CH101-03-01 module in a flat plate measuring at least 100 mm in
diameter. An example mounting plate is shown in Figure 6, where the sensor has been inserted into a 5.3 mm diameter hole has been
drilled in a 1 mm thick plastic plate measuring 135 mm x 175 mm.
Can someone explain to me the purpose of this plate?