////They did a similar trick with the humpback whale - fascinating stuff, but not really 'sound' as we know it, until it's processed. A bit like tickling the colours up on astronomy photographs I suppose.///

Yes, but you were saying earlier that they were cheating with a synthesizer. There's nothing wrong with adjusting the frequencies into the audible range or there would be nothing to hear. Then you brought up the stereo thing and I've already pointed out a legitimate sferics recording in stereo. I don't know how they do it and don't care but obviously it can be done at least in some instances. I would also imagine that signals coming from nearby planets would be far richer in audio quality than the rather sterile sounds we get from pulsars which are immense distances away.