An acoustic radar uses any loudspeaker to emit sound pulses toward a target. A microphone or the same speaker then receives the return. You can use any oscilloscope to experiment with it.
Any handheld "ultrasonic" distance meter operates the same way. To use a miniature sound emitter, ultrasonic devices have a diameter of ~ 2 cm, and the meter can measure distance to targets (walls, windows) up to ~ 15 meters.
I have no schematic available but in one old design a triggered counter was used to measure the interval between the sent pulse and echo in ~ 10-cm steps. Now you can program your computer to do the same.