The speaker and microphone of my Android phone have stopped working, but the headphone jack still works. I don't want to always use a headphone, so I removed everything from a discarded non-smart phone, and soldered a headphone jack to its speaker and microphone, in order to use it as an extension to the phone.
Now I can comfortably use it, but people calling me can hear their own voice as an echo.
People at the other end speak -> my speaker -> my microphone catches it -> they hear their voice back
I tried lowering the speaker's volume to minimum, but that does not stop the issue. I am not even using the ringer speaker. I also tried putting some cotton on the speaker and the microphone, but that does not help either.
The issue persists irrespective of whether the top cover is there or not.
How can I prevent this from happening?