Over-inflation of a part of the lungs (emphysema can cause this)
Reduced airflow to part of the lungs
There are several types of abnormal breath sounds. The 4 most common are:
Rales. Small clicking, bubbling, or rattling sounds in the lungs. They are heard when a person breathes in (inhales). They are believed to occur when air opens closed air spaces. Rales can be further described as moist, dry, fine, and coarse.
Rhonchi. Sounds that resemble snoring. They occur when air is blocked or air flow becomes rough through the large airways.
Stridor. Wheeze-like sound heard when a person breathes. Usually it is due to a blockage of airflow in the windpipe (trachea) or in the back of the throat.
Wheezing. High-pitched sounds produced by narrowed airways. Wheezing and other abnormal sounds can sometimes be heard without a stethoscope.
Kraft M. Approach to the patient with respiratory disease. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 83.
Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.