When auscultation is performed, pleural rubs can often be heard as creaking or grating sounds. These are produced by two inflamed surfaces rubbing against each other - similar to walking on fresh snow or the sound of leather-on-leather. Coughing does not affect these noises and they will usually change in intensity with respiration cycle (aimilarly increasing at inspiration, decreasing at expiration). A crucial distinction between them and pericardial friction rubs is that those continue even when patient holds their breath whilst a pleural rub stops immediately thereafter.