Sound Echo Problem

I am building native android app.I try voice call between two Android devices. But i get too much echo noise.But when i use headphone it works fine.

The issue mentions native Android voice calls between two devices, with echo absent when using headphones, but names no files, tests, or entry points. Start by reproducing the call without headphones and inspect the example app's audio-call path; done requires identifying a reproducible cause and confirming that device-to-device calls no longer produce excessive echo.

Written by the indexing model from the issue text.