Classification and terms
How do you give the right name to a sound you hear?
Short answerFirst decide: is this sound part of the breath sound that is always there, or is it a sound added on top of it? Then describe the sound, and name it last.
Which sounds do we separate at the examination?
The normal sounds from the previous module are always there in the background at the examination. Adventitious sounds are added on top of them. So listen to the two separately at every point.
The absence of adventitious sounds does not mean the examination is normal, because the background breath sound also carries findings. This sound may be diminished, may differ between the two sides or may be heard as bronchial breathing over the periphery.
Adventitious sounds fall into two large families. Continuous adventitious sounds are long and musical. Discontinuous adventitious sounds are short and explosive. Squawk and pleural friction rub do not fit neatly into this division, so they sit in a separate group.
Basic breath sounds
Continuous adventitious sounds
Discontinuous adventitious sounds
Other sounds
A wheeze with a single tone is called monophonic, and a wheeze with several tones is called polyphonic. The third rule sums up how these sounds arise: narrowing makes music, opening makes a crackle, friction makes a creak (How do adventitious sounds arise?).
The details of the basic sounds are in the The four normal breath sounds lesson. In short, as the stethoscope gets closer to the trachea and large bronchi, the sound becomes louder and higher-pitched, and expiration becomes longer.
What do adventitious sounds sound like?
The table sums up the most distinctive feature of each adventitious sound and what you should think of first. The details are in three lessons: Telling continuous sounds apart, Describing crackles and Squawks and pleural friction rubs.
| Sound | How and when is it heard? | What does it suggest? |
|---|---|---|
| Wheeze: monophonic, polyphonic | A musical sound. Mostly in expiration. | Asthma, COPD. At a single site, local narrowing. |
| Rhonchus | Low-pitched and rough. Mostly in expiration. | Secretions. May change with coughing. |
| Stridor | A loud tone, strongest over the neck. Mostly in inspiration. | Narrowing of the larynx or trachea. Assess urgently. |
| Fine crackles | Short, relatively high-pitched crackles. In mid-to-late inspiration. | Fibrosis, congestion. |
| Coarse crackles | Longer, low-pitched and louder crackles. Mostly in early-to-mid inspiration. | Bronchiectasis, secretions, pneumonia. |
| Squawk | A short musical sound. Sometimes a crackle is heard just before it. In inspiration. | Hypersensitivity pneumonitis and other interstitial lung diseases. |
| Pleural friction rub | A creak. Mostly in both phases. | Pleurisy. The patient may have pleuritic pain. |
Why does the same sound go by different names?
In clinical practice and in older textbooks, you will meet different names for the same sound. To avoid confusion, write the recommended international term in your note and add the features of the sound.
| Recommended term | On this site | Older terms you may hear |
|---|---|---|
| Fine crackles | Fine crackles | crepitations, fine rales, "Velcro" crackles |
| Coarse crackles | Coarse crackles | coarse rales, coarse crepitations |
| Wheeze | Wheeze (monophonic or polyphonic) | sibilant rhonchi, musical rhonchi |
| Rhonchus | Rhonchus (plural rhonchi) | sonorous rhonchi |
| Pleural friction rub | Pleural friction rub | pleural rub, friction rub |
| Bronchial breathing | Bronchial breathing | tubular breathing |
| Squawk | Squawk | squeak |
On this site, we call the normal sound over the manubrium bronchial breath sound. If the same sound is heard over the lung periphery, it is called bronchial breathing (The four normal breath sounds).
How do you describe a sound?
Describe the sound first, then name it. A sound name is not a diagnosis. It tells you how the sound is heard. To describe it, ask the four questions we use in every lesson.
In inspiration or in expiration? At the start or at the end of the phase?
Musical or explosive? Low-pitched or high-pitched?
In which region, and how widespread?
Does it change with coughing or with a deep breath?
Weak note: "Pneumonic crackles on the right."
Good note: "Coarse crackles over the right lower zone posteriorly, in mid-to-late inspiration, unchanged by coughing. Bronchial breathing over the same area."
The weak note makes a diagnosis but does not describe the sound. The good note points you, or the colleague who takes over on call, to the same sound a week later. For details, see the A good examination note lesson. To practise, use the findings note writer.
Do clinicians give the same sound the same name?
Not always. Even experienced clinicians may give different names to the same recording. In an international study, clinicians named wheezes more consistently than crackles. In the ERS reference collection study, the weakest agreement was for recordings with low-pitched wheezes or rhonchi. So write the features of the sound next to its name.
- At every point, listen separately to the background breath sound and to adventitious sounds. Even without adventitious sounds, the background sound may carry findings.
- Adventitious sounds form two families. Continuous sounds are long and musical, and discontinuous sounds are short and explosive.
- You will hear different names for the same sound. In your note, write the international term and the features of the sound.
- Describe the sound first, then name it: When? What does it sound like? Where? What changes it?
- Clinicians do not always agree on the name of a sound. So write its features next to the name as well.
Going deeperresidents · specialists · numbers and sources
CORSA and ERS criteria
The CORSA definitions, published in 2000, introduced acoustic criteria for computer analysis. The 2016 ERS reference collection then matched the terms to audiovisual examples. Laennec's terms had been translated differently from country to country. As a result, rale, rhonchus and crepitation had taken on different meanings in different traditions.
| Sound | Approximate quantitative feature | Typical phase |
|---|---|---|
| Wheeze | In CORSA, usually >100 Hz and >100 ms. The limits vary. | Mostly expiratory |
| Rhonchus | <300 Hz and >100 ms, periodic waveforms that die away quickly. Overlaps with low-pitched wheeze. | Mostly expiratory |
| Stridor | Often high-frequency. No useful threshold on its own. | Mostly inspiratory |
| Fine crackles | IDW ≈ 0.7 ms, 2CD ≈ 5 ms | Mid and late inspiration |
| Coarse crackles | IDW ≈ 1.5 ms, 2CD ≈ 10 ms | Early and mid inspiration, variable |
| Squawk | According to CORSA, the duration rarely exceeds 400 ms. No universal duration threshold. | Inspiratory |
| Pleural friction rub | Broadband. No defined threshold. | Inspiration, expiration or both |
The values are approximate reference criteria. They overlap with each other and are not disease-specific thresholds. IDW is the initial deflection width, and 2CD is the two-cycle duration.
How well do observers agree?
Twenty-eight observers from seven countries classified 120 recordings. Within-group agreement for crackles ranged from 65% to 87% (Conger's kappa 0.20 to 0.58). For wheezes, agreement ranged from 69% to 99.6% (kappa 0.09 to 0.97). The median group kappa was about 0.49 for crackles and about 0.62 for wheezes (Aviles-Solis et al., 2017).
Very short crackles can be lost in the background breath sound. An algorithm trained on inconsistent labels may also learn the disagreement between observers rather than the biology.
See the reference list for sources.
Check yourself
3 short questions. The explanation opens when you choose an answer.