[Electronic Stethoscope 2]

I am sure that my microphone is biass in this circuit,beaucuse befure this circuit,I test Electronic stethoscope circuit , I could hear my sounds in 8 ohms speaker,but there were so much noise that I couldn t hear heartsounds .
after that I test electronic stethoscope 2 , I couldn t  hear my sounds(I mean my speaking sounds) and I couldn t hear heartsounds too but I put the stethoscopehead  on my neck and I could hear some frequencies and when I rub stethoscope I coud hear it sounds,so I thing my problem is mic,(it has 2 wire) :'( ??? :(
maybe there is problem beetwin mic and stethoscope head,Should I past and press them togather ?

This is very urgently,I should finish it next week.
thanks.

[Electronic Stethoscope 2]

Hello
I couldent hear heartsounds,I think that the problem is the mic that I used,
I used very ordinary capacitor microphon but a small one beaucase I put it
to the sleeve rabber of stethoscope,
I want to ask what is the electret mic exactly (in electronic stethoscope 2)?