Sorry to be the bearer of bad news on this one but regarding audio on a web-site - if you can hear it on the web then you can save it to your computer.
Doesn’t matter if it is streamed or played through a Flash mp3 player or anything else. If a person wants the audio then they can 100% get it if they really want it.
You may be able to hide the URL to a certain extent but in most instances there are ways around this and unfortunately should the worst come to the worst then you can easily record whatever is playing on your computer to an mp3 file using one of the many programs available on the internet. The only effective thing you can really do is lower the quality enough that people wouldn’t want to keep it as the quality just wouldn’t be nice enough for them to use.
Sorry for being the bearer of bad news, nearly 100% of the time I come in here and try to help out as much as I can but on this one there really is no effective way of stopping people getting the audio if they are determined enough.
All that was said with my audio producer hat on 😉
Best wishes,
Mark