What is "venous hum"

Hum \Hum\, n.

1. A low monotonous noise, as of bees in flight, of a swiftly revolving top, of a wheel, or the like; a drone; a buzz.

   The shard-borne beetle with his drowsy hums.
   --Shak.

2. Any inarticulate and buzzing sound; as:

   1. The confused noise of a crowd or of machinery, etc., heard at a distance; as, the hum of industry.

      But 'midst the crowd, the hum, the shock of men.
      --Byron.

   2. A buzz or murmur, as of approbation.
      --Macaulay.

3. An imposition or hoax.

4. [Cf. Hem, interj.] An inarticulate nasal sound or murmur, like h'm, uttered by a speaker in pause from embarrassment, affectation, etc.

   These shrugs, these hums and ha's.
   --Shak.

5. [Perh. so called because strongly intoxicating.] A kind of strong drink formerly used. [Obs.]
   --Beau. & Fl.

   Venous hum. See under Venous.

Venous \Ven"ous\, a. [L. venosus, from vena a vein. See Vein.]

1. (Anat.) Of or pertaining to a vein or veins; as, the venous circulation of the blood.

2. Contained in the veins, or having the same qualities as if contained in the veins, that is, having a dark bluish color and containing an insufficient amount of oxygen so as no longer to be fit for oxygenating the tissues; -- said of the blood, and opposed to arterial.

3. Marked with veins; veined; as, a venous leaf.

   Venous leaf (Bot.), a leaf having vessels branching, or variously divided, over its surface.

   Venous hum (Med.), a humming sound, or bruit, heard during auscultation of the veins of the neck in an[ae]mia.

   Venous pulse (Physiol.), the pulse, or rhythmic contraction, sometimes seen in a vein, as in the neck, when there is an obstruction to the passage of blood from the auricles to the ventricles, or when there is an abnormal rigidity in the walls of the greater vessels. There is normally no pulse in a vein.

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 clavicle.

This may be confused with a heart murmur. The venous hum is heard throughout the cardiac cycle. The difference is easily detected by placing a finger on the jugular vein when listening to the heart, which will abolish or change the noise. A true heart murmur will be unaffected by this maneuver. The murmur also disappears when the patient is in the supine position 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.