A control unit 11 responds in ordinary course to external stimuli. In addition, the control unit 11 further processes the external stimuli to characterize and otherwise seek to identify certain aspects and attributes. Unique audible signals that correspond to varying results of such analysis are then provided. These audible signals can readily facilitate ease and accuracy when diagnosing the cause of a particular operational issue. In one embodiment the diagnostic audible signals are selectively mutable without concurrently muting other audible signals as correspond to ordinary operation of the control unit 11.