Venous hum is a benign auscultatory phenomenon caused by the normal flow of blood through the jugular veins.
Typically, a peculiar humming sound is heard in the upper chest near the clavicle, emanating from the supraclavicular fossa just lateral to the sternocleidomastoid muscle, usually more obviously on the right side than on the left.
[2] Though the exact mechanism is still unclear, it has been suggested that the hum occurs when otherwise silent laminar flow through the internal jugular vein is disturbed by deformation of this vessel at the level of the transverse process of the atlas during head rotation.
It may be easier to hear when sitting, when the chin is elevated, or when the head is rotated contralaterally (away from the location of the sound); deep inspiration and hyperkinetic circulatory states (e.g. hyperthyroidism) can also increase its intensity.
Abnormal and potentially serious conditions such as thyrotoxicosis and anemia, by augmenting blood flow through the jugular veins, can nonetheless initiate or reinforce the venous hum, making it more noticeable,[4] and manipulation of the sound with various maneuvers has often helped physicians discover and diagnose cardiovascular disorders.