1. Stridor:

Stridor is a continuous, high-pitched, crowing sound heard predominantly on inspiration. The cause of this sound is generally the partial obstruction of the larynx or trachea. Stridor may be heard in conditions such as croup and foreign body obstruction. It’s typically loudest over the anterior neck, as air moves turbulently over a partially-obstructed, upper airway.

2. Wheeze:

The sound of a wheeze is a high-pitched, continuous musical sound. This is caused by air passing through an obstructed, narrow airway. The classic wheeze may be referred to as a sibilant wheeze. This refers to the high-pitched, whistle-like sound. Alternately, what we often refer to as rhonchi is the sonorous wheeze, which refers to a deep, low-pitched rumbling or coarse sound, as air moves through tracheal/bronchial passages in the presence of mucus or respiratory secretions. It is commonly heard in the lungs during expiration. It may be heard in asthma, emphysema and chronic bronchitis.

3. Crackles:

Crackles are also known as alveolar rales. The sound crackles create are fine, short, high-pitched, intermittently crackling sounds. The cause of crackles can be from air passing through fluid, pus or mucus. It is commonly heard in the bases of the lung lobes during inspiration. Crackles can be further categorised as coarse or fine. Coarse crackles sound quality is low-pitched and moist; it may be heard in pulmonary oedema and bronchitis. Fine crackles sound quality is like hair rubbing near the ear and may be heard in congestive heart failure and pulmonary fibrosis.

4. Pleural Rub:

The pleural rub sound results from the movement of inflamed pleural surfaces against one another during chest wall movement. The sound quality is considered a harsh grating or creaking. Potential causes include tuberculosis and pneumonia. It is best heard in the lower anterior lungs and lateral chest, during both inspiration and expiration.