Background noise in Adc input

Dear all
thank you for your time to read my topic

i'm working on project to record audio I managed to record audio at a sample rate of 16 kHz and a super good 48kHz with STM32F103C8. But the problem is that I have background noise in the recorded sound. and I used different methods

I used a digital power supply
And I used a battery instead of a power supply, but nothing changed
I checked the microphone amplifier with an oscilloscope , great
I use short wire for analog input and low noise standard

Does anyone have experience with ADC noise?

Did you check the power supply? Did you check the noise to see if it is regular/periodic, or random? Did you turn off all the lights to see if the noise was affected? Did you use shielded wire for all the audio connections, with only ONE ended grounded to the Arduino? Do all the ground connections terminate at a single point? Are the signal wires kept far away from any power wires?
Lots to do if any answer is no.

I did all these things

This is my voice and you can see the noise (11.2 KB)

No, I am not going to download a zip file. And your voice is not the noise. Please tell us if your scope shows the noise as regular or is impulse. A picture of the scope trace would also be helpful.


Try a .01 uf cap across the mike wire to ground.

What you show in reply #7 is probably not ADC noise.

To measure the ADC noise, remove the microphone and connect a 10K resistor from the analog input to ground. Use the shortest possible leads.

I tried this it works but I can only get a positive peak

So, the problem lies not with the ADC, but with the input coupling and microphone. Post a complete schematic.

Also post a clear, closeup photo showing the actual setup.

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The capacitive coupling leaves the ADC input floating. The ADC input must be biased positive by a resistive voltage divider, say 10K/10K between GND and the ADC reference voltage.

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Sorry, my phone has run out of battery I can not send you photos at this time

It is now clear what the problem is.

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Thank you very much

Now I try it

If you wired the microphone circuit on a breadboard, expect it to pick up AC and RF noise from the environment. It is better to use a small microphone module on a PCB.

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Do you mean that?