How do i remove noises in heartsound?

[audioguru]

So i should increase op amp gain with changin the resistors?

Gain resistors? Guess what? Your circuit has VERY LOW GAIN because Vref is a high impedance. Add a capacitor to fix it.
I find that there is an improved LM358B available now. Its input current is much less than the older ordinary LM358. Then your older LM358 will have less gain with the high value of 1M for your gain resistor. The new LM358B still produces a lot of hissss noise.

 

[audioguru]

Did you notice in the schematic of my electronic stethoscope how I mounted the mic?

 

[Bdsdbehdad]

Gain resistors? Guess what? Your circuit has VERY LOW GAIN because Vref is a high impedance. Add a capacitor to fix it.
I find that there is an improved LM358B available now. Its input current is much less than the older ordinary LM358. Then your older LM358 will have less gain with the high value of 1M for your gain resistor. The new LM358B still produces a lot of hissss noise.

Sorry my friend i cant understand. Like shematic i use lm386 and tl072 op amp. You said i use lm358m

 

[rjenkinsgb]

I used the top of bottle that my mic dont toch skin or chest directle.

Do you have a diaphragm or membrane sealed across the front of that, though?

 

[audioguru]

Sorry, this thread started from another person with another schematic.
My electronic stethoscope circuit has plenty of gain, more than 300 times.
I did not use a membrane in front of my mic because the chest is vibrated by the heartbeats.

 

[SobhanJahanipsrast]

Use a bandpass filter