Table 1.

Classification of abnormal lung sounds.

	Mechanism of sound production	Location	Characteristics	Acoustics	Related diseases
Fine crackles	Unrelated to secretions	Peripheral lung	Discontinuous High-pitched Inspiratory	Rapidly dampened wave deflection Frequency: about 650 Hz Shorter duration (about 5 ms)	Interstitial lung fibrosis Pneumonia Congestive heart failure
Coarse crackles	Intermittent airway opening, related to secretions	Peripheral lung	Discontinuous Low-pitched Inspiratory	Rapidly dampened wave deflection Frequency about 350 Hz Longer duration (about 15 ms)	Same as fine crackles but usually more advanced disease
Wheezes	Narrowed airway Flow limitation	Bronchi	Continuous High-pitched Expiratory > Inspiratory	Sinusoid Frequency > 100–5000 Hz Duration > 80 ms	Asthma COPD Tumor Foreign body
Rhonchus	Rupture of fluid films of secretions Airway wall vibrations	Bronchi	Continuous Low-pitched Expiratory > Inspiratory	Sinusoid Frequency about 150 Hz Duration > 80 ms	Bronchitis Pneumonia
Stridor	Narrowed airway	Larynx, Trachea	Continuous High-pitched Inspiratory	Sinusoid Frequency > 500 Hz	Epiglottitis After extubation Foreign body
Pleural friction rub	Pleural inflammation	Chest wall	Continuous Low-pitched Inspiratory and expiratory	Rhythmic succession of short sounds Frequency < 350 Hz Duration > 15 ms	Pleurisy Pericarditis Pleural tumor