Upon auscultation, this sign is an extra heart sound of to-and-fro character, typically with three components, two systolic and one diastolic.
[1] It resembles the sound of squeaky leather and often is described as grating, scratching, or rasping.
The inner and outer (visceral and parietal, respectively) layers are normally lubricated by a small amount of pericardial fluid, but the inflammation of pericardium causes the walls to rub against each other with audible friction.
In children, rheumatic fever is often the cause of pericardial friction rub.
Pericardial friction rubs can also be heard in pericarditis that is associated with uremia or post-myocardial infarction.