I have a Voip based app. So i thought of customizing SipDroid open source project. As the starting phase i have changed all the package names, Class names etc. It perfectly works on my Samsung Galaxy Y. But i tried with many other mobiles, Voice is not audible. Call is being initialized but could not hear voice. In Samsung galaxy young, voice is clearly audible for both incoming and outgoing calls. But in all the other phones i have tested i can hear only beep sounds. What could be the problem?

I tried calling the other mobile(that has Sip Droid) with my Samsung Galaxy Young(customized app) I could hear voice in my app but could not hear in Sipdroid. But when i tried calling Sipdroid to Sipdroid, it works fine in all the mobiles.