not the least possibility

[Anonymous]

Hi,

I am not quite understand the underlined phrases. Could anyone do me a favor?

Television newsreels will, of course, continue to develop and be of the greatest interest and attraction, but there is surely not the least possibility that they will ever replace the news on sound.

Thanks a lot.

[Tdol]

surely not the least possibility means that the writer thinks it is impossible, but there is a tiny hint of doubt.
I don't know the meaning of 'on sound', I'm sorry- I'll try to find out and come back.