Audio feature to be added in my ip cam viewer app

Hello, We are working on our Institute project in which I am trying to create my own app in java/android which will view the video captured by IP camera I have bought and two way audio feature will be also added. I have completed the video phase, as I used a screenshot url which gets refresh after every miliseconds so it seems like a video streaming, but we are stuck in sound feature. I am not sure how to add two way audio feature so that we can communicate as well. Do any one of you can guide us in this? We have a low budget as this is just a project of our university. Thank you!