Ans. b. S3Ref Ganong's Review of Medical Physiology 2511' edn; Page no. 542Hea SoundsCauseCharactersSite of auscultationPhonocar- diogramECG correlation51-Vibrations set up by suddenclosure of AV valvesat the sta of ventricular systole, during phaseof isovolumetric contraction. Long & soft LUBB Duration -0.15 sFrequency- 25 - 45 HzBest heard over mitral and tricuspid areaSingle group of 9-13 waves - rescendoand diminuendo series of wavesCoincides with peak of R wave52 - Vibrations with closure ofsemilunar valves ust at the onset of ventricular diastole.Heard as a single sound during expiration but during inspiration the increased output of the right hea causes a physiological splitting. Sho,loud High Pitched DUBB Duration0.12 s Frequency 50 HzBest heard over aoic and pulmonary area Single group of 4-6 waves having same amplitudeCoincides with end of T wave CauseCharactersSite of auscultationPhonocar- diogramECG correlation53 -- Vibrations set up in cardiac wallby inrush of blood during rapid fillingphase of ventricular diastole. It may be heard duringlate pregnancy. In children and young adults, is a normalfinding.Sho, soft Low pitched Duration --0.1 sNormally cannot be heard byauscultation with stethoscope 1-- 4 waves grouped togetherAppears between T and P waves54 -- Vibrations set up during atrialsystole Coincides with last rapid filling phaseof ventricular diastole. Examples include concentrichyperophy, aoic stenosis, and myocardial infarction. Sho, low pitched Duration -- 0.03 sFrequency --3 HzNormally cannot be heard by auscultationwith stethoscope1-2 waves with very low amplitudeCoincides with interval betweenend of P wave and onset of Q wave