What are Adventitious Breath Sounds?

Adventitious breath sounds are abnormal lung sounds heard in the chest, typically with a stethoscope. They can provide clues that help diagnose pulmonary (relating to the lungs) or heart diseases. Some adventitious breath sounds can be heard without the help of a stethoscope. These sounds can be described as rattles, crackles (also called rales), wheezes (sometimes referred to as rhonchi), pleural rubs, and stridor.

Adventitious breath sounds can often be the first sign of illness in a variety of conditions, including infection (such as pneumonia, an infection that inflames the air sacs in one or both lungs), interstitial lung disease (a group of disorders that result in the scarring of lung tissues), pulmonary edema (excess fluids in the lungs), or chronic obstructive pulmonary disease (COPD).

Adventitious Breath Sounds

Verywell / Laura Porter


Auscultation is the process of listening to the sounds of the lungs, heart, or other organs using a stethoscope. Auscultation of the lungs, also known as chest auscultation, is usually performed by a healthcare provider, who can diagnose or rule out conditions based on sounds coming from particular areas of the lungs.

Lung sounds can be heard in all areas of the chest, including above the collarbones and at the bottom of the rib cage. The healthcare provider performing the auscultation may hear normal breath sounds, decreased or absent breath sounds, or adventitious breath sounds in the process.

The exam is best done in a quiet area, and may require the chest and back to be exposed. The person being examined is usually seated in a chair or on the side of the bed for auscultation. Breath sounds will be different depending on which part of the lung the air is moving through.

Types of Breath Sounds

Breath sounds are the noises produced by the structures of the lungs during the process of breathing. These sounds are then transmitted to the trachea (windpipe) and bronchi (the air passages that lead from the trachea to the lungs).

There are a few types of breath sounds, including:

  • Tracheal sounds: These sounds are heard over the trachea. They are harsh and loud.
  • Bronchial sounds: These sounds are high-pitched and hollow-sounding. They move through the front of the chest through the bronchioles, which branch out from the trachea.
  • Vesicular sounds: These are soft sounds. They come from parts of the lung involved in gas exchange.
  • Bronchovesicular sounds: These medium-pitched sounds come from the back of the chest.

Types of Adventitious Breath Sounds

Adventitious breath sounds typically indicate an underlying medical condition. They can be described as continuous (heard with every inhale and exhale) or intermittent (heard infrequently or with inhalation or exhalation). Sounds can also vary by pitch. The characteristics of the breath sounds can help a healthcare provider distinguish between the different sounds to narrow down the possible causes of these sounds.


Wheezing is a continuous and high-pitched whistling sound. It is caused by fluttering air movements produced either through a narrowing or partial obstruction of or pus or accumulated fluids within the smaller airways (like bronchioles). Wheezing sounds can sometimes be heard without a stethoscope.


Rhonchi is a term that is sometimes used interchangeably with wheezing, but the sound is coarser, lower-pitched, and louder compared with wheezing. The sound is similar to snoring. Like wheezing, rhonchi is caused by fluttering air movements but through the larger airways (like the bronchi).


Crackles, also known as rales, occur during inhalation and are irregular. The sound of crackles is generally high-pitched with clicking or rattling. It may also sound like “crumpled cellophane.” Crackles may be lower-pitched if the larger airways are affected. These sounds can be further described as moist, dry, fine (high-pitched), or coarse (lower-pitched). They are caused by smaller airways (and sometimes larger airways) snapping open when breathing in.

Pleural Friction Rub

Also referred to as pleural rub, pleural friction rub is s continuous, low-pitched, grating, and harsh sound. It sounds similar to rhonchi, but emanates from a specific area of the chest or lung, as opposed to more generalized grating sounds. Pleural friction rub is caused by the friction of inflamed pleural membranes during movement of the chest wall from inhalation and exhalation.


This sound is caused by the narrowing of the airways. It can be heard with inhalation and is intermittent (on and off). Stridor is high-pitched and noisy with wheezing-like sounds emanating from the upper airways, especially around the larynx and pharynx. It is more common in children because their airways are softer and narrower. 

Causes of Adventitious Sounds
 Type Sound Possible Causes
Wheezing/rhonchi Musical, high-pitched Asthma, croup, COPD, foreign body
Crackles/rales Deeply pitched, coarse Heart failure, pneumonia, chronic bronchitis
Pleural rub Non-musical, grating, creaky Lung membrane inflammation, lung tumor
Stridor (adults) Variable, high-pitched Epiglottitis, foreign body, laryngeal edema
Stridor (children) Variable, high-pitched Croup, a foreign body
To a layperson's ear, abnormal lung sounds may sound the same, but they differ in pitch and texture. Those differences can indicate a particular condition.

Snoring, squawking (an abbreviated wheezing sound that can occur with pneumonia), and whooping (associated with whooping cough) are also considered adventitious breath sounds. 


A variety of tests can be performed to evaluating how well the lungs are functioning and the potential causes of adventitious breath sounds, including blood tests, imaging, and pulmonary function tests.

Blood Tests

A blood culture can be used to test for bacteria in the bloodstream. The blood tests a healthcare provider may order to evaluate adventitious breath sounds include:

  • Arterial blood gas (ABGs): Tests the levels of oxygen and carbon dioxide in the blood. It checks how well the lungs are able to move oxygen into the blood and remove carbon dioxide from the blood.
  • Complete blood count (CBC): Measures many different parts and features of the blood, including red blood cells and hemoglobin, which carry oxygen from the lungs to the rest of the body. It checks for infections, anemia, and diseases of the immune system.
  • Natriuretic Peptide Tests (NT-proBNP): Performed only if heart failure is suspected. Measures the levels of brain natriuretic peptide and N-terminal pro b-type natriuretic peptide in the bloodstream. High levels can mean the heart isn't pumping as much blood as the body needs.


Different types of imaging are commonly used to diagnose conditions like acute pulmonary embolism, advanced COPD, and pneumonia.

The imaging that is commonly ordered to evaluate lung function includes:

  • Chest X-ray: Allows a healthcare provider to study the structure of your lungs and the condition of your thoracic cavity
  • CT scan: Provides more detailed pictures of the lungs than chest X-ray
  • Echocardiogram: Uses sound waves to create pictures of the heart's chambers, valves, walls, and the blood vessels (aorta, arteries, veins) attached to the heart

Pulmonary Function Tests

Pulmonary function tests are a group of noninvasive (does not require putting instruments into the body) tests that evaluate the quality of a person's breathing and how well their lungs are functioning when abnormal lung sounds are heard.

The different pulmonary function tests include:

  • Spirometry: Measures how much air you exhale and how quickly you exhale
  • Exercise stress test: Evaluates the lungs and heart under conditions of increased metabolic demand (during exercise)
  • Pulse oximetry: Measures the oxygen carried in the blood cells
  • Sputum culture: Checks for bacteria or another type of organism that may be causing an infection in the lungs or the airways leading to the lungs

A healthcare provider may begin with a pulmonary function test, which measures the flow of air throughout the lungs and how well they work. Some of the spirometry values your healthcare provider will discuss with you include:

  • Forced vital capacity (FVC): The amount of air an individual is able to forcibly exhale from their lungs after taking the deepest breath they can
  • Total lung capacity (TLC): The total volume of air in the lungs after a maximal inhalation
  • Forced expiratory volume (FEV): The amount of air a person can exhale during a forced breath
  • Forced expiratory flow 25% to 75% (FEF25-75): The average forced expiratory flow rate over the middle 50% of the FVC, which is the total amount of air exhaled during the FEV test

Normal values will vary based on your age, sex, height, and ethnicity. Typically, a value below 80% of your predicted value is considered abnormal.

If the results show abnormal lung function, there may be enough information for your healthcare provider to diagnose a condition, such as asthma or COPD. If more data are needed, additional tests such as a CT scan or ABGs may be ordered.

When to Call a Healthcare Provider

Adventitious breath sounds alone do not indicate a particular diagnosis or provide a clue to the severity of a condition. If you experience wheezing, especially if it is persistent, call your healthcare provider. Call 911 if abnormal breathing sounds develop rapidly and occur with the following:

  • Severe shortness breath
  • Dizziness or fainting
  • Rapid or irregular heartbeat
  • Nasal flaring
  • Cyanosis (skin turning blue)
11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Carisa Brewster
Carisa D. Brewster is a freelance journalist with over 20 years of experience writing for newspapers, magazines, and digital publications. She specializes in science and healthcare content.