A microphone assembly includes an acoustic sensor configured to produce an electrical signal and an electrical circuit including a voice activity detector coupled to an output of the acoustic sensor. The microphone assembly further includes an internal clock signal generator and a host interface coupled to the electrical circuit. The host interface has external connections including an external clock signal and a data connection. The microphone assembly includes an acoustic activity detection mode of operation when the electrical circuit is clocked by the internal clock signal generator in the absence of an external clock signal at the host interface. The microphone assembly has a plurality of operating modes controlled by an external clock signal received in response to an interrupt signal provided by the electrical circuit. The electrical circuit is configured to provide data representing the electrical signal at the host interface when the external clock signal is received.