I have been informed that the Spectrum Next version has a background hissing noise when run on the Cspect and MAME emulators (thanks for spotting this Leonis, and your investigations into the cause). If this affects you, you can download the new Cspect version above. It plays a short bleep at the start to make the sound behave itself. Otherwise, it's identical to the original release. Or you can turn the sound down on your speakers, as the game doesn't have any sound effects anyway :-)