Severe tinnitus keeps me awake at night. I already have two dedicated sound-machines which emit an allegedly relaxing, synthesized ocean surf sound; but want a recording of the real thing. I'll transfer it onto a USB-stick to play via a stereo. The recording must run for at least six hours, please. I don't want the sound of monstrous seas crashing against rocks – who could sleep with that racket? – or the other extreme of very gentle waves just about managing to lap up the beach. 'Rollers', I think they used to be called: that's what I'm after.