Multiple Helmholtz resonance apertures are proposed to enhance the output pressure of air-coupled capacitive micromachined ultrasonic transducers (CMUTs) for non-contact ultrasound imaging applications. The methodologies of defining the design parameters of CMUTs and the resonant apertures on the membrane of CMUTs are discussed. In comparing certain configurations of resonant apertures with conventional CMUTs, simulation results show that a prospective improvement of output pressure (up to 32.1%) can be achieved.