What core technique did the manual sphygmomanometer utilize for readings?

Listening for Korotkoff sounds

The foundational technique that became the gold standard for the early non-invasive measurement using the sphygmomanometer involved auscultation, which is the act of listening for specific auditory markers in the artery. These distinct sounds, known as Korotkoff sounds, are audible in the artery specifically as the pressure within the inflatable cuff is gradually released after occlusion. This method required a skilled observer with a stethoscope to accurately identify the point where sounds began (systolic) and where they completely disappeared (diastolic). This process formed the critical baseline for measuring pressure without resorting to invasive techniques, even though it was strictly a clinical procedure.