Its an interesting one.
The "ethereal noise" at the start is overdubbed by the video poster. The actual broadcast started with the static and the voice.
However, the broadcast was investigated by the UK broadcasting authorities who drew a blank over it.
Bear in mind that this was a short wave television signal that was interrupted over quite a wide area. It takes a considerable amount of transmitting
power to do that, and that kind of stuff was not freely available to "joe public" in the 70's - if it was you can bet a whole lot more hoaxes would
have happened.
As for the effect on the voice, we're talking the 1970's here. That kind of stuff was limited fairly well to places like the BBC Radiophonic
Workshop, professional recording studios and
maybe the odd university studio. There were NO windows computers back then, the most advanced
thing that you could buy in the UK computing wise was a Sinclair calculator.
Even more interestingly, no one has ever claimed any kind of responsibility for it at all - which is unusual these days.
So to me, it was either a very well covered up inside job or something very very weird indeed. Its one of those wonderful enduring mysteries that will
one day probably have a rational explanation.... or will it?
[edit on 2/0407/07 by neformore]