Audio and Particles?

EDIT, TOO VAUGE

I would like to create a part / model that will give off a sound of a generator, that will gradually fade as you walk away. I do not know how to test when a player enters a radius, thus playing a sound to them. I would need the script and where specifically I put them. (Music is playing in the background with a LocalScript, if that matters) Secondly, I would like to create a particle (I think?) that will seem like it is snowing, but will not go through objects such as models or parts. I know how to do custom particle and make a part large and transparent, making it seem like it's snowing but it is not what I am looking for. This may be the only way, I am not sure. Sorry for not being clear. Thanks.