From a sound artist standpoint, I am also thrilled about this noise, as technical devices like amplifiers, loudspeakers, or if you record electromagnetic frequencies, will share this sound quality too. Think of those test noises, e.g. pink noise, making you feel relaxed — this simple trick of nowaday’s parents to play pink noise sound to their babies to calm. But there is also the sound of the speakers themselves, and sometimes I really enjoy just listening to their own signals sitting in a studio, it’s their presence, I guess. But cat sounds are natural (in a way), they purr in an irregular way, the sound follows their breathing rhythm, stopping shortly to swallow. I read about the purpose of purring, and its frequency range is 25 to 150 Hertz, deep bass sound. It is said, that these frequencies are used for stress relief and bone healing. If you go on YouTube, you will find lots of videos, dealing with this topic of sound healing, bone healing, etc. and you will also find some videos of small or cute kittens purring being recorded with a binaural microphone.