An apparatus includes a housing having a printed circuit board having a top surface and a bottom surface. The top surface of the printed circuit board forms an outer surface of the housing. The apparatus further includes a bottom-port microphone sensor mounted on the bottom surface of the printed circuit board. The printed circuit board has a port opening formed therein to provide an acoustic path from outside of the housing to the microphone sensor. A method of detecting ultrasonic signals includes receiving ultrasonic signals within a port opening of a printed circuit board forming part of a surface of a housing, and directing ultrasonic signals to a microphone sensor secured to a printed circuit board through the port of the printed circuit board.