Abnormal Breathing Sounds: Types and Causes

What counts as an abnormal breathing sound

Normal breathing is almost silent at the mouth. Through a stethoscope it sounds like a soft rustle over most of the chest. Doctors call any extra noise heard on top of (superimposed on) these normal breath sounds an adventitious sound. They also note when normal breath sounds are reduced or absent, which can mean air or fluid around the lung, or a collapsed section of lung.

Abnormal sounds fall into two groups:

• Continuous sounds last a quarter of a second or more and have a musical pitch: wheezes, stridor and rhonchi.
• Discontinuous sounds are short pops or clicks: crackles.

Where the sound is loudest, whether it happens breathing in or out, and whether it clears with coughing all help pinpoint the cause.

Types of abnormal breathing sounds

Wheezes

A wheeze is a high-pitched, whistling or musical sound, usually loudest when breathing out. It means air is being forced through narrowed small airways in the lungs. You can often hear it without a stethoscope.

• Common causes: asthma, COPD, viral chest infections, bronchiolitis in babies, and allergic reactions.
• Clue: wheezing that improves after a reliever inhaler suggests asthma or COPD. Wheezing on one side only can mean a blockage, such as an inhaled object or a tumor.
• Warning sign: in severe asthma the chest can go quiet because so little air moves. A "silent chest" is an emergency.

Stridor

Stridor is a loud, harsh, high-pitched sound, usually when breathing in. It comes from a narrowing in the upper airway: the voice box (larynx) or windpipe (trachea). It is heard clearly without a stethoscope.

• In children: croup is the most common cause, with a barking cough. Inhaled objects and epiglottitis are rarer but dangerous. In babies, a floppy voice box (laryngomalacia) causes stridor that is usually harmless and outgrown by age 2.
• In adults: severe allergic swelling, throat infections or abscesses, vocal cord problems, tumors and injury to the neck.
• Stridor at rest always needs urgent assessment because the airway may be close to closing.

Crackles (rales)

Crackles are brief clicking, popping or rattling sounds, mostly when breathing in. They are made when small airways and air sacs, stuck shut by fluid or stiffened by scarring, suddenly pop open.

• Fine crackles sound like hair rubbed between your fingers near the ear, or like Velcro. They occur in heart failure (fluid at the lung bases) and in interstitial lung disease such as pulmonary fibrosis.
• Coarse crackles are lower, wetter and bubbling. They occur in pneumonia, bronchiectasis and bronchitis.
• A few crackles at the lung bases that clear after deep breaths or coughing can be normal, especially in older or bedbound people.

Rhonchi

Rhonchi are low-pitched, snoring or rattling sounds caused by mucus in the larger airways. They often clear or change after coughing, which separates them from crackles. They are common in bronchitis, COPD and chest infections. Many doctors now group rhonchi with wheezes and call them "low-pitched wheezes".

Pleural friction rub

A creaking or grating sound, like leather rubbing on leather, heard breathing in and out. It means the two inflamed layers of the lining around the lung (the pleura) are rubbing together. Causes include pleurisy, pneumonia, blood clots in the lung and lupus. It is often accompanied by sharp chest pain on breathing.

Other noises you can hear yourself

• Snoring and gurgling: vibration of the soft palate and tongue during sleep. Loud snoring with pauses and gasps suggests sleep apnea.
• Whoop: a long, high-pitched intake of breath after a coughing fit is typical of whooping cough (pertussis).
• Grunting: a short grunt at the end of each breath in a baby is a sign of serious breathing difficulty.
• Rattling in the throat: pooled saliva or mucus, common in very ill or dying patients, and in babies with colds.
• Squeaks: short, high-pitched sounds late in a breath, heard in some lung scarring conditions.

Quick comparison of abnormal lung sounds

Symptoms that come with noisy breathing

• Fever and cough with colored mucus: infection, such as pneumonia or bronchitis.
• Breathlessness on exertion, swollen ankles, waking breathless at night: heart failure.
• Wheeze with itchy skin, hives or lip swelling: allergic reaction.
• Barking cough and hoarse voice in a young child: croup.
• Slowly worsening breathlessness and a dry cough over months: lung scarring.
• Daytime sleepiness and morning headaches with loud snoring: obstructive sleep apnea.

How doctors assess abnormal breath sounds

A doctor listens with a stethoscope over the front, sides and back of the chest while you breathe deeply through your mouth. They may ask you to cough, then listen again. They will ask when the noise started, whether it is constant or comes and goes, what triggers it, and whether you smoke or have asthma, heart disease or allergies.

Common tests:

• Pulse oximetry: a fingertip clip measuring oxygen levels.
• Peak flow or spirometry: measures airway narrowing in asthma and COPD.
• Chest X-ray: for pneumonia, fluid, heart enlargement or masses.
• Blood tests: infection markers and BNP, a heart failure marker.
• CT scan: for scarring, bronchiectasis or a blockage.
• Laryngoscopy or bronchoscopy: a camera to look at the voice box or airways, used for stridor and suspected inhaled objects.

Treatment

Treatment targets the cause, not the sound itself:

• Asthma and COPD: reliever inhalers open the airways quickly, and preventer inhalers reduce inflammation.
• Croup: a single dose of steroid medicine reduces swelling. Severe cases get nebulized epinephrine in the ER.
• Pneumonia: antibiotics for bacterial infection, plus oxygen if levels are low.
• Heart failure: diuretics (water pills) remove fluid from the lungs, alongside long-term heart medicines.
• Anaphylaxis: an epinephrine auto-injector immediately, then emergency care.
• Sleep apnea: weight loss, sleeping position changes or a CPAP machine.

At home, for mild noisy breathing with a cold, rest, fluids and humid air may ease mucus. Do not give cough and cold medicines to children under 6. Avoid smoke, and if you smoke, stopping is the single most effective way to reduce wheezing and long-term lung damage.

Frequently asked questions

What are the 4 types of abnormal breath sounds?

The four main types are wheezes (high-pitched whistles from narrowed airways), stridor (harsh noise from the upper airway), crackles or rales (popping from fluid or scarring in the air sacs) and rhonchi (low rattles from mucus). A pleural friction rub, from inflamed lung lining, is often listed as a fifth.

What is the difference between a wheeze and stridor?

A wheeze comes from narrowed small airways in the lungs and is mostly heard breathing out. Stridor comes from the voice box or windpipe and is mostly heard breathing in. Stridor is generally more urgent, because a narrowing high in the airway can close off breathing quickly.

What do crackles in the lungs mean?

Crackles mean small airways or air sacs are popping open against fluid, mucus or stiff scar tissue. Coarse, wet crackles with fever suggest pneumonia. Fine crackles at both lung bases suggest heart failure or pulmonary fibrosis. A doctor needs to examine you and usually order a chest X-ray.

Are abnormal breathing sounds always serious?

No. A rattly chest during a cold, snoring, or crackles that clear after a cough are often harmless. But noisy breathing with difficulty breathing, blue lips, stridor at rest or a grunting baby is an emergency. New wheezing or crackles that persist should be checked by a doctor.

Why does my breathing make a noise when I lie down?

Lying down can let mucus pool and the tongue and soft palate fall back, causing gurgling or snoring. Wheezing or crackles that start when lying flat and ease when sitting up can signal heart failure or acid reflux. If you wake breathless or need extra pillows, see a doctor.