Echo Cancellation Software

Is there any way to cancel echo caused from sound comming from an external speaker into a macbook’s built in mic. I need a software solution; I cannot use an eco cancellation mic.

I have built a system for people who have vision and hearing loss at the same time so they can feel the sounds in their environment through a large speaker. However the feedback is too heavy. Any suggestions?

Thanks

Llain

Are you using the inbuilt mic as a recording source for your system?

Thats right, it's a powerbook mic. I decided to use it because it picks up very slight sounds even across the room. And the computer amplfies the sound to a level that is strong enough to drive the speaker. It works brilliantly other than the feedback.

The thing is I know it works because MSN Messenger voice chat for PC and Skype have software solutions for echo cancelation. I just need this solutin to apply to all of the sounds the computer is processing.