Certain non-pulmonary sounds may be heard during auscultation of the chest. It is important to be familiar with non-pulmonary sounds, such as mediastinal crunch and pleural friction rubs.

• Mediastinal crunch is caused by pneumomediastinum. This sound is characterized by precordial crackles that correlate with the heartbeat rather than respiration. The patient can be asked to temporarily cease respiration to appreciate this difference.
• Pleural friction rub results from the movement of inflamed and roughened pleural surfaces against one another during movement of the chest wall.  This sound is non-musical, and described as “grating,” “creaky,” or “the sound made by walking on fresh snow.” Inflammation or neoplasia can cause thickening of the pleural surfaces, which then creates more friction when sliding along one another, creating this sound. Any potential cause of pleural effusion, pleuritis, or serositis can result in a pleural friction rub (i.e., inflammation, neoplasm). Patients may be able to describe the localization of the rub based on pain. A pleural friction rub is a manifestation of pleural disease, though its absence does not exclude this pathology.

Reference
Bickley, L. S., Szilagyi, P. G., Hoffman, R. M., & Soriano, R. P. (2021). Bate’s Guide to Physical Examination and History Taking (13^th ed.). Wolters Kluwer Health: Philadelphia.