Abstract: An apparatus for treatment of a respiratory condition, the apparatus comprising: a pressure generator configured to generate a flow of breathable gas; an intermediate component pneumatically connected to an air delivery tube, the intermediate component comprising a port configured to facilitate propagation of sound outside of the intermediate component; a sensor attached externally to the intermediate component and located adjacent to the port of the intermediate component, the sensor configured to sense sound propagated through the air delivery tube; and a controller. The controller can be configured to: receive a sound signal generated by the sensor as a result of sensing sound during operation of the apparatus, analyse the received sound signal, and effect a response based at least in part on the analysing.