These words describe some of the sounds that a doctor might hear when he listens to your lungs with the stethoscope. Rales are produced by the passage of air through bronchi that contain secretions or are constricted by spasm or thickening of their walls. May be heard on inspiration (breathing in) or expiration (breathing out). Rales are further broken up into 18 different classifications depending on the sound heard and it's location in the chest. Rhonchi are rales or rattling in the throat, especially when it resembles snoring. Velcro pops are a new term I heard a doctor say for the first time today, can't tell specifically what it means yet.