Sorry I have taken so long to get back to you. I'd never tried to use that particular site from the point of view of using a screen reader. I certainly found that the visual heart was much easier to understand than the text; I'm also not sure which way round they were developed - whether they had the text & put in the Flash - which is what I thought they had done, or whether they had the Flash and put in the text to support it. (It's now also quite old).
I have to say that I thought that they had sound, but it's quite a long time since I used that particular site - and when I checked that it was still live, I was doing it on a PC that doesn't have sound.