The 'Korotkoff sounds' are the sounds that a doctor or nurse listens for when they are taking your blood pressure. They are named after Dr. Nikolai Korotkoff, a Russian physician who described them in 1905, when he was working at the Imperial Medical Academy in St. Petersburg.

They are detected by listening with a stethoscope placed over the brachial (arm) artery just below a blood pressure cuff, as it is gradually deflated from a pressure high enough to occlude the artery and stop the blood flowing. As the cuff pressure reaches systolic pressure, the blood starts to flow, and a whooshing sound is heard (the first phase of the Korotkoff sounds). As the cuff is deflated further, the artery opens and closes, and the flow of blood is turbulent, so sounds are still heard. When the cuff pressure is less than the diastolic pressure, the artery is open all the time, and the flow of blood is smooth, and the sounds disappear.

Systolic pressure is registered as the pressure at which the sounds are first heard, and diastolic as the pressure at which they disappear (phase 5 of the Korotkoff sounds).