The sound of rain outside relaxes me and makes me sleep better too. In fact, it makes me tired even during the day and I have a tendency to sleep much longer on rainy days.
I would play the rain sound that was posted in the white noise thread (I think it was you who posted it, redrobin, thanks for the link!) in the background while sleeping, but then again I think like this:
If I run my PC at night, my parents will become angry (for obvious reasons, they pay for the power after all), if I play it through my audio equipment, I wouldn't want it to be too loud to bother my parents (it is not as close to my bed as my PC which is basically next to it and I often use it when in bed and the audio equipment faces the door, my parents sleep just on the other side of the short corridor in front of my room, there is the bedroom) and more importantly, this is draining power as well and I do not want them to pay more just for this, I would feel guilty and have a bad feeling doing so. I feel like I already drain enough power with my hobby/special interest/obsession which is level design and hence I use my PC non-stop in my spare-time, sometimes at the max. capacity.
The ventilation in our house has a soothing sound (subtle bass), which also does the job a bit, but I really prefer rain sounds. I would put the sound on my mp3-player, but I hate to sleep with something stuck in my ears, so that is no option for me (other than that the battery would not survive the night as it is already quite old and can only stay on for a few hours).
I can also sleep very well if there is no sound at all, ear plugs would do it, but as I mentioned before I dislike the feeling of having something in my ears at night.
Nibs, I think heartbeat is a very relaxing sound, do you notice those silicon ear plugs or are they so soft that you do not feel them at all? 
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Diagnosed with Aspergers.
BSP-errors are awesome.