friction sound n.
The sound heard on auscultation caused by the rubbing together of two opposing serous surfaces that are roughened by an inflammatory exudate. Also called friction rub.
The friction sound is produced by the rubbing together of roughened surfaces and is characteristic of pleurisy.
When the dry stage is succeeded by the exudation of fluid this friction sound disappears.
But during the time the friction sound is lost a sound which has been called a "churning noise" may take its place.