The present disclosure is generally directed a system to detect activation phrases within input audio signals transmitted over a low-bandwidth network. The system can use a two-stage activation phrase detection process. First a sensing device, which can include a plurality of microphones for detecting an input audio signal, can detect an input audio signal that includes a candidate activation phrase. Second, the sensing device can transmit the recordings of the input audio signal to a client device for confirmation that the input audio signal includes the activation phrase.