lung sounds should be listened for during initial vital signs, after that they should be assessed with each set of vital signs, after any breathing treatment, or if audible change is detected, as a basic the locations to listen would be the apexs and flanks of each side, we are listening for rales, rhonci, wheezes,stridor etc.....all of these sounds are associated with a certain disorder. for example wheezes is a good indicator or an asmatic and stridor is an indicator of airway obstruction