I wake to the sound of a moan by my left ear. It’s the usual night-time shtick; I was sinking into a half-sleep, accompanied by the sounds of tinnitus and the CPAP machine hissing when this roused me. This happens so often it’s become the norm. It used to scare me, until I started dismissing the experiences as hypnagogic hallucinations – there: classifiable, safe, and unimportant. But some of them shake me – like this one. And the reason is it sounds so much like something occupying physical space in my everyday world, rather than some projection of an overactive subconscious kicking it up as my logical mind tries to…