The vibration of the vocal chords as air circulates through the respiratory system makes different sounds depending on the conditions of the airways. Lung auscultation is the assessment of such noises through the use of tools like the stethoscope. Lung sounds may be abnormal or adventitious, meaning that noises may sound layered. These problematic noises may be caused by bronchitis, asthma, a foreign body, pneumonia, heart failure, and chronic obstructive pulmonary disease (COPD). Due to the severity of some of these possible causes, healthcare professionals should have the ability to quickly identify the different lung noises so that underlying issues may be addressed.
The Guide to Lung Sounds
Ronchi (Rattles)
Continuous, low-pitched, coarse, rattling sound
Heard on both inhalation and exhalation
Usually caused by a blockage or secretions in upper airway
Location: trachea & bronchi
Stridor
Continuous, high-pitched wheezing sometimes described as “musical”
Mostly inspiratory but may be heard on exhalation
Caused by disrupted airflow, croup, infection, or a foreign object
Location: trachea & bronchi
Wheezing
High-pitched expiratory noise; may be heard without a stethoscope
Caused by narrowed airways
Associated with asthma and COPD
Location: throughout entire lung
Rales (Crackles)
Discontinuous bubbling/popping that may sound similar to pulling apart velcro
Heard on inhalation and can be further described as coarse, fine, moist, or dry
May be caused by collapsed airways and/or alveoli “popping open”
Location: lower lobes
Pleural Friction Rubs
Low-pitched, grating, or creaking heard during exhalation
Caused by inflamed pleural surfaces rubbing against each other