Which is true about heart sound?
Ans. B First heart sound has maximum durationHeart soundFrequencyDurationAssociated eventFirst heart25-45 Hz0.15 secClosure of A-V valves--onset of ventricular systoleSecond heart sound50 Hz0.12 secClosure of semilunar valves--onset of ventricular diastoleThird heart soundLow0.1 secFirst rapid filling phase of ventricular diastoleFourth heart soundBelow 20 Hz0.1 secLast rapid filling phase of ventricular diastole due to atrial contraction