From the University of Sydney, Bachelor of Design Computing website, See My Voice was a project by one of the students in the program, Andrea Lau.

SeeMyVoice - Social Information/Data Visualisation (or infovis). SeeMyVoice visualises chat transcripts stored by MSN Messenger. It aims to highlight people's style of chatting and increase understanding of our online social interaction. Each person is represented by a coloured wave which ebbs and fluctuates according to message length and the time taken between messages.

Great job Andrea! That's exactly how IM conversations go.

UPDATE: Andrea has a complete website describing her work and the See My Voice project in much more detail.