sound [L, sub, under, unde, wave] , an emission detected by an instrument used to locate the opening of a cavity or canal, to test the patency of a canal, to ascertain the depth of a cavity, or to reveal the contents of a canal or cavity. A sound is used to determine the depth of the uterus, to detect stones in the bladder, and, less commonly, to assist in correctly inserting a urinary catheter in the urethra through the urinary meatus.
