Make a sound fade?

Ok i got this looping rain sound, the problem is it starts and ends suddenly, i just want it to mildly fade in and out, is it possible to archive that without modifying the sound itself (therefore compromising the loop) outsinde c2?

I believe I've done that before with an instance variable. When it was due to fade out I set a the variable to Time. Each tick when that variable was set, it would set the volume of the sound to Volume-(Variable-Time) or something like that. (resetting the variable when sound was low enough.) But I can't find where I did that ATM to be specific.

Another method, since it is a white noise, would be to play a separate fade out rain sound, and stop the original sound.

I was thinking about the second method, it would make the sound slightly longer and eng a bit later than when suposed, but it would definitely work.