An electronic device may include a substrate and an acoustic actuator mounted on a surface of the substrate. More particularly, the acoustic actuator may be configured to generate displacements along a direction parallel with respect to the surface of the substrate in response to an electrical signal applied thereto. A speaker box may define an acoustic volume, and the speaker box may include a speaker box wall with a speaker box opening therethrough adjacent the acoustic actuator. A speaker membrane may be provided across the speaker box opening adjacent the acoustic actuator, and the speaker membrane may be mechanically coupled to the acoustic actuator so that the speaker membrane is configured to deflect responsive to displacements generated by the acoustic actuator. Related methods are also discussed.