Hi all Ihave made the original ,the corrected and the elect. steth. 2 about one year ago The original didn t work and the other two worked. The best one was the corrected circuit. The stethoscope should hear the sounds between the 1st and 2nd , and the 2nd and 1st heart sonds , like murmours as systolic and diastolic , also clicks and so on. So there shoud be no noise . I hope to find a new project using 3v supply and a small head phone like that used with mobile . This will be more practical and I can use it in my clinic. Thanks to all especially audioguru.