Systems and methods of sensing audio with a MEMS microphone that modulates a frequency of a phase-locked loop. The MEMS microphone includes a movable electrode and a stationary electrode. The movable electrode is configured such that acoustic pressures acting on the movable electrode cause movement of the movable electrode. A voltage-controlled oscillator of the phase-locked loop is coupled to the MEMS microphone and receives a control signal. The voltage-controlled oscillator also generates an oscillating signal based on the control signal and a capacitance between the movable electrode and the stationary electrode. A phase detector of the phase-locked loop receives and determines a phase difference between the oscillating signal and a reference signal. The phase detector further generates the control signal based on the phase difference. A controller is configured to receive the control signal and determine an audio signal based on the control signal.