Abstract: A speaker array includes a first speaker device having a first membrane and a first acoustic channel, the first membrane being configured to oscillate and generate a first ultrasonic acoustic signal configured to be transmitted at least partially in the first acoustic channel, the first acoustic channel including at least one dimension comparable to a dimension of a viscous boundary layer of air. A second speaker device includes a second membrane and a second acoustic channel, the second membrane being configured to oscillate and generate a second ultrasonic acoustic signal configured to be transmitted at least partially in the second acoustic channel, the second acoustic channel including at least one dimension comparable to the dimension of the viscous boundary layer of air. An audio output of the speaker array is the combined output of at least the first speaker device and the second speaker device.