An acoustic module is coupled to an acoustic passage. The acoustic module includes an acoustic transducer coupled to a diaphragm. A controller or other circuitry measures an impedance of the acoustic transducer. Based on the impedance, the controller determines whether the impedance indicates that the acoustic passage is blocked. The controller may determine that the acoustic passage is blocked by liquid that is present in the acoustic passage. When the controller determines based on the impedance that liquid is present in the acoustic passage, the controller may drive out, purge, and/or otherwise remove the liquid, such as by using the acoustic transducer to vibrate the diaphragm.