biology

Phonomyography

Phonomyography is a biology 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 Phonomyography rather than just read about it. In short: Phonomyography (PMG) (also known as acoustic myography, sound myography, vibromyography, and surface mechanomyogram) is a technique to measure the force of muscle contraction by recording the low frequency sounds created during muscular activity. Although, until recently, less precise than the more traditional mechanomyography, it is considerably easier to set up.

Key takeaways

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

Reference excerpt

Phonomyography (PMG) (also known as acoustic myography, sound myography, vibromyography, and surface mechanomyogram) is a technique to measure the force of muscle contraction by recording the low frequency sounds created during muscular activity. Although, until recently, less precise than the more traditional mechanomyography, it is considerably easier to set up. The signal is measured using condenser microphone elements, piezoelectric sensors, accelerometers, or a combination of sensors attached to the skin. Hydrophones have also been used to measure muscles immersed in water. Improvements in microphones and contact transducers (piezoelectric devices), as well as recording systems, has meant that they have become available in a size and of a quality that enables them to be applied to a normal daily setting outside the clinic and the laboratory setting. These new possibilities provide a clinical tool for the assessment of patients with musculoskeletal complaints during daily activities, or assessment of athletes in terms of efficiency in use of muscles. The sound created by muscle movement can be heard with the ear pressed up to a contracting muscle, but most of the energy is low frequency, below 20 Hz, making it inaudible infrasound. Electromyography signals are typically bandpass filtered from 10 Hz to 500 Hz, by comparison. PMG signals are limited to 5 Hz to 100 Hz in some experiments. Orizio states that the low-frequency response of the sensor is the most important feature, and should go as low as 1 Hz. Images of PMG waves are available in this creative commons-licensed document, "Mechanomyographic amplitude and frequency responses during dynamic muscle actions: a comprehensive review".

History Muscle sounds were first described in print by the Jesuit scientist Francesco Maria Grimaldi in a posthumous publication of 1665, which influenced the work of the English physician William Hyde Wollaston and the German scientist Paul Erman. The latter enlisted the aid of René Laennec. Mechanical amplification was first employed by Hermann von Helmholtz. The past two centuries of repeated rediscovery and neglect of the phenomenon were summarised by Stokes and Blythe in 2001.

References

8. Harrison, A.P., Danneskiold-Samsøe, B., Bartels, E.M. - Portable acoustic myography – a realistic noninvasive method for assessment of muscle activity and coordination in human subjects in most home and sports settings. Physiol Rep. Jul 2013; 1(2): e00029. Published online Jul 10, 2013. http://physreports.physiology.org/content/1/2/e00029

Worked examples

Example 1 — a first encounter with Phonomyography

Start with the simplest possible case. Write down what Phonomyography claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, 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 Phonomyography 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 Phonomyography 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 Phonomyography

In research: Phonomyography appears in biology 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 Phonomyography 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: Phonomyography is common in secondary-school and first-year university syllabi. It links to neighbouring topics Medical tests, Neurology procedures, Neurophysiology, so understanding it makes those chapters shorter.
In everyday life: Look for Phonomyography 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 Phonomyography in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Phonomyography 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 Phonomyography out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Phonomyography in simple terms?

Why does Phonomyography matter?

Because it connects several biology 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 Phonomyography?

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 Phonomyography.