The audio recordings of Swami Vivekananda from The Parliament of Religions, 1893, Chicago:
Welcome Address - Vivekananda : Swami Vivekananda : Free Download & Streaming : Internet Archive
are very interesting.
The source seems difficult to trace. Does anybody have more details about this?
Some have raised doubts as to whether it is actually Vivekananda's voice.
You hear a lady introducing Vivekananda, and the loud applause. Further the voice is quite forceful, melodious and distinct (and not with American accent), so why should it not be his voice?