That's quite a big task you've given yourself. In fact, my impression is that you're fundamentally underestimating what is involved. The only way I could see "the solution" provided to you in a forum post is if that post pointed you to a $20,000 software package that you could integrate in your web app.
Servlets and JSPs will have very little to do with it. Obviously you will need some client-side component that can record sound - if you want to use Java that would mean an
applet (with all the security issues that come with that). Otherwise Flash might be an option. This client-side component then needs a server-side component to which it sends the compressed audio, and the server needs to have an open connection to some other client to which to send this audio where it would be decompressed and played.
That's the view from 10km up - there are lots of hard problems to solve before you'd have something decent. Because of that I predict that you will end up not doing this. Maybe add a chat functionality instead?