Certified ailurophile[0] here. I've found the gentle hum of purring very soothing, almost like having a hot chocolate on a cold day, or chicken soup. It's very comforting, and I'm lead to believe the specific frequency of the hum is in line with nature and The Universe itself. It has the same frequency of the Omm mantra which is apparently the frequency our bodies emit when we're in full health and homeostasis or in a meditative trance.