Crackles are a common sound auscultated in the lungs. They are also sometimes referred to as crepitations, or rales. Crackles are caused by the sudden opening of smaller airways and alveoli collapsed by fluid or secretions. Crackles are classified by several different factors.
Their pitch and sound characteristics
- Fine- high pitched and brief
- Medium
- Coarse- lower pitched and more prolonged
Where they occur in the breathing cycle
- Inspiratory (common)
- Expiratory (less common)
A few common causes of crackles include:
- Pneumonia
- Bronchitis
- Pulmonary Edema
- Atelactasis
When trying to explain the sounds to someone who has never heard it before I personally describe the sound as being similar to the sound of a plastic bag being rustled.
A good example of crackles can be found in this video: