Pleural friction (rubbing) sounds may be heard in pleuritis cases, although the sounds are lost when a significant effusion is present. These are usually fine crackling, crunching or creaking sounds that are heard mainly at end inspiration/early expiration.

What lung sounds are heard with pleural effusion?

bronchial breath sounds and bronchophony, egophony, and whispered pectoriloquy may be heard over the area of the lung that is compressed near the effusion.

What causes crackles in the lungs?

Crackles (rales) are caused by excessive fluid (secretions) in the airways. It is caused by either an exudate or a transudate. Exudate is due to lung infection e.g pneumonia while transudate such as congestive heart failure.