Venous hum is a benign phenomenon. At rest, 20% of the cardiac output flows to the brain via the internal carotid and vertebral arteries. This drains via the internal jugular veins. The flow of blood can cause the vein walls to vibrate creating a humming noise which can be heard by the subject. Typically, a peculiar humming sound is heard in the upper chest near the collarbone.

This may be confused with a heart murmur

Heart murmur

Murmurs are extra heart sounds that are produced as a result of turbulent blood flow that is sufficient to produce audible noise. Most murmurs can only be heard with the assistance of a stethoscope ....

. The venous hum is heard throughout the cardiac cycle. The difference is easily detected by placing a finger on the jugular vein

Jugular vein

The jugular veins are veins that bring deoxygenated blood from the head back to the heart via the superior vena cava.-Internal and external:There are two sets of jugular veins: external and internal....

 when listening to the heart, which will abolish or change the noise. A true heart murmur will be unaffected by this manoeuvre. The murmur also disappears when the patient is in the supine position

Supine position

The supine position is a position of the body: lying down with the face up, as opposed to the prone position, which is face down, sometimes with the hands behind the head or neck. When used in surgical procedures, it allows access to the peritoneal, thoracic and pericardial regions; as well as the...

or may disappear if the subject turns their head to one side. It is also known by the names "nun's murmur" and "bruit de diable" (the Devil's noise).

While a venous hum may provoke consultation with a health care professional, it is entirely harmless.