[andrewas]

Black holes do emit radiation - Stephen Hawking would be the man to talk to about that. Or rather, 'Brief History of Time' and 'Universe in a Nutshell' would be the books to read. Wossisname Krauss speaks of it in 'Physics of Startrek' and 'Beyond Startrek' as well. Its all to do with virtual particles and imaginary energy and weird quantum stuff that can happen in areas of space with a steep gravity gradient.

Thats low level though. What is being detected is from the accretion disc, not the hole itself. Its radiation generated by the matter falling into the black hole and getting heated in the process. Of course sound cannot travel in a vacuum, so I suspect the 'sound waves' are low frequency EM waves rather than actual sound.

As for the far side of a black hole, thats pure speculation. I dont think black holes have any far side. And if one did, both ends would be singularites, so both ends would be black holes and thus it dosent matter to the outside universe anyway.