I'm a part-time asthmatic. I've had a couple of major attacks in my life and a few minor ones. Nothing too recent, though.
In the grips of asthma it's difficult to sleep, nigh impossible without an inhaler. One of the reasons for this is that you can hear your own wheezing, and for obvious reasons this sounds like a respiratory red flag. It makes you aware of just how much you're not breathing well.
But in good health, or passable health, you also hear your own breath. Especially when laying down to sleep. It is, if all goes well, more calming in these circumstances. Worth noting if only because it's something you tend to ignore the rest of the day.