An acoustic sensor configured to non-invasively detect acoustic vibrations associated with a medical patient. The acoustic vibrations are indicative of one or more physiological parameters of the medical patient. The acoustic sensor can include a sensor support and at least one sound sensing membrane supported by the sensor support. The membrane can be configured to detect acoustic vibrations associated with a medical patient. The membrane may also be configured to produce a membrane signal corresponding to the acoustic vibrations when the acoustic sensor is attached to the medical patient. The acoustic sensor can also include a probe-off assembly supported by the sensor support. The probe-off assembly can be configured to produce a probe-off signal responsive to attachment of the acoustic sensor to the medical patient and detachment of the acoustic sensor from the medical patient.
