Abnormal Lung Sounds and Causes

A breath sound, also known as a lung sound, is the sound produced by your lungs whenever you inhale and exhale. These may be heard on their own or with a stethoscope.

There are normal breath sounds that your healthcare provider expects to hear. Abnormal breath sounds may indicate a respiratory illness, heart disease, infection, or other problems. The types of breath sounds—most commonly wheezing, stridor, rhonchi, or rales—can provide clues as to the underlying cause.

This article explains where breath sounds originate and what wheezing, stridor, rhonchi, and rales mean. It also describes possible causes and when it is time to seek medical care.

Normal Breath Sounds

Auscultation is the process of listening with a stethoscope. With lung auscultation, your healthcare provider will listen for different sounds as you inhale, known as inspiration, and exhale, known as expiration.

As part of the evaluation, the provider will check for three types of normal breath sounds.

Tracheal Breath Sounds

Tracheal breath sounds are loud and high-pitched and are heard primarily over the trachea (windpipe). The sounds are often described as being harsh as if air is being blown through a pipe.

Tracheal sounds are heard when the stethoscope is placed on the upper part of the sternum (breastbone) or between the scapulas (shoulder blades).

Bronchial Breath Sounds

Bronchial breath sounds are caused by the two large airways, called bronchi, that deliver oxygen to the lungs. These sounds can be heard when the stethoscope is placed over the middle part of the sternum or in the middle of the back between the scapulas.

The sounds are higher-pitched than those heard over other parts of the lungs. However, they are also quieter and more hollow-sounding than tracheal breath sounds.

Vesicular Breath Sounds

Vesicular breath sounds are sounds heard over the main body of the lungs. Vesicular breath sounds originate in the tiny air sacs of the lungs, called alveoli. They produce soft, low-pitched sounds mainly during inspiration.

Vesicular breath sounds are best heard when the stethoscope is placed on either side of the spine beneath the scapula.

Wheezing

Wheezing describes whistling sounds that are usually more pronounced with expiration. These sounds may be “squeaky” (when high-pitched) or “moaning” (when low-pitched).

Wheezing may also be described as “musical” when there is a single note or multiple variable notes. Single notes suggest a disease in the smaller airways, while multiple notes suggest a disease in the larger airways.

“Squawks” may describe very short wheezes that usually occur late during inspiration.

There are many possible causes of wheezes. They include:

Stridor

Stridor refers to a high-pitched, continuous sound with a musical quality that is heard mostly with inspiration. It is typically loudest around the neck area and usually occurs when there is some sort of blockage in the upper airways.

Stridor should be assessed as a matter of urgency. In some cases, it may indicate a potentially life-threatening obstruction of the airways.

Causes of stridor include:

• Epiglottitis (inflammation of the flap of cartilage behind the tongue)
• Tracheomalacia (collapse of the trachea)
• Laryngomalacia (collapse of the larynx, or voicebox)
• Croup (an infection that causes swelling in the upper airways)
• Tracheal stenosis (narrowing of the trachea)
• Foreign body aspiration in the upper airways

Stridor in any of these situations should be regarded as a sign of a medical emergency.

Rhonchi

Rhonchi, in contrast to wheezes, cause low-pitched clunky or rattling sounds. They sometimes resemble snoring and will often clear with coughing.

Rhonchi are usually caused by the build-up of mucus in the large airways. Many of the same conditions that cause wheezing can also cause rhonchi. Even so, rhonchi generally occur when the disease is more advanced and starts to clog the airways with mucus.

Causes of rhonchi include:

• Pneumonia
• Bronchiectasis
• Chronic bronchitis (a symptomatic stage of COPD)
• Emphysema (a more advanced stage of COPD)
• Cystic fibrosis (an inherited disorder characterized by the overproduction of mucus)

Rales

Rales, also known as “crackles” or crepitation, are rattling, crackling, clinking, or popping sounds that occur when collapsed alveoli suddenly snap open during inspirations. The sounds can come and go but are most pronounced when you inhale.

Crackles can be further described as “fine” or “coarse.” Fine crackles are related more to the small airways, while coarse crackles are related more to the large airways.

Potential causes of rales include:

Less Common Sounds

Wheezing, stridor, rhonchi, and rales are the most commonly heard breathing sounds, but there are other lung sounds aligned with specific diseases.

Whooping Cough

Whooping cough (pertussis) is an infectious respiratory disease that is less common than it used to be thanks to vaccines. But it does still affect children in the United States quite regularly.

With pertussis, a high-pitched “whooping” sound may be heard after coughing. The sounds, called inspiratory gasps, are typically broken up by hacking coughs

Pleural Rub

A pleural rub, also known as a pleural friction rub, is a gritty sound that arises when the membranes lining the lungs, called pleura, are inflamed and rub against each other. A pleural rub is likened to the sound of walking on fresh snow or sitting down on a leather couch.

A pleural rub may occur during both inhalation and exhalation. Unlike rales, the sound does not clear with coughing.

Conditions associated with a pleural rub include:

When to See a Healthcare Provider

Abnormal lung sounds that are persistent or worsening should be seen as a matter of urgency. In some cases, a specialist in respiratory diseases called a pulmonologist may be needed.

Lung Examination

In addition to auscultation, there are other components of thorough lung evaluation. These include a physical exam to check your respiratory rate, depth of breathing, pattern of breathing, and symmetry of your chest as you expand the lungs.

The healthcare provider may also percuss (tap) your chest and back. This helps determine if your lungs sound fluid-filled (such as with pneumonia) or hollow (such as with bronchiectasis). Any chest tenderness may be a sign of a fracture or a torn muscle or ligament.

Additional lab and imaging tests may be ordered, including:

Other Signs of Lung Disease

There are other things a healthcare provider would look for when investigating the cause of abnormal lung sounds. These include signs like:

• Finger clubbing (associated with lung cancer or interstitial lung disease)
• Nasal flaring (widening of the nostrils when you can’t get enough air in)
• Intercostal retractions (when the skin between your ribs pulls inwards as you inhale)
• Bradypnea (abnormally slower breathing)
• Tachypnea (abnormally rapid breathing)