I'm interested in knowing how is the directivity of the typical microphones and loudspeakers found in smartphones and tablets affected as they operate in the near ultrasound region (18-21 kHz). Near ultrasound region smartphone's transducers compliance has been recently added to android OS so that manufacturers can rate their devices according to whether they have this feature or not (see). I've been doing some research and I've found that nowadays most used microphones are MEMS. I would like to know:
- How does the directivity behaves in these transducers even though the only available data belong to transducers not yet inside the smartphone case?
- What is the manufacturing technology of smartphones' speakers?
- What is the diameter of the microphone's and speakers diaphragm ?