science

Venous hum

Venous hum is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Venous hum rather than just read about it. In short: Venous hum is a benign auscultatory phenomenon caused by the normal flow of blood through the jugular veins. At rest, 20% of cardiac output flows to the brain via the internal carotid and vertebral arteries; this drains via the internal jugular veins.

Key takeaways

Venous hum belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Venous hum to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Venous hum from memory before moving on to harder problems.

Reference excerpt

Venous hum is a benign auscultatory phenomenon caused by the normal flow of blood through the jugular veins. At rest, 20% of cardiac output flows to the brain via the internal carotid and vertebral arteries; this drains via the internal jugular veins. The rush of blood from these veins to the brachiocephalic vein can cause the vein walls to vibrate, creating a humming noise which can often be heard by the subject. 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. The sound may radiate to the upper sternal border on either side. 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. The venous hum is heard throughout the cardiac cycle, though is typically louder during diastole. 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. It may be loud enough to result in audible pulsatile tinnitus. It is by far the most common type of normal continuous murmur, universal in healthy children, and frequently present in healthy young adults, especially during pregnancy. The humming may be confused with a heart murmur, which may be a symptom of a potentially serious condition. The difference is easily detected by placing light pressure on the internal jugular vein when listening to the heart, which will immediately abolish or change the venous hum, whereas 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" (noise of devils). While a venous hum may provoke consultation with a healthcare professional, the hum itself is entirely harmless and is the product of ordinary cardiac physiology. 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, and manipulation of the sound with various maneuvers has often helped physicians discover and diagnose cardiovascular disorders.

See also Venus Hum, American electronic pop band which derives its name from this phenomenon

References

External links Page about Venous hum Archived 2010-07-19 at the Wayback Machine Medical Education for Visual Learners - Cervical Venous Hum

Worked examples

Example 1 — a first encounter with Venous hum

Start with the simplest possible case. Write down what Venous hum claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Venous hum before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Venous hum ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Venous hum

In research: Venous hum appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Venous hum in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Venous hum is common in secondary-school and first-year university syllabi. It links to neighbouring topics Heart, Heart murmurs, so understanding it makes those chapters shorter.
In everyday life: Look for Venous hum outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Venous hum in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Venous hum means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Venous hum out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Venous hum in simple terms?

Why does Venous hum matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Venous hum?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Venous hum.