Techniques described herein generally include methods and systems related to a MEMS-based audio speaker system configured for generating an audio signal. The speaker system includes one or more apertures in the speaker system positioned to receive the ultrasonic carrier signal and one or more movable and over-sized obstruction elements that are configured to modulate the ultrasonic carrier signal and thereby generate an audio signal. Because the movable obstruction elements are configured to overlap one or more edges of the apertures when in the closed position, modulation depth of the generated audio signal can be substantially improved or otherwise varied.