One of my cats cat never reacts to the TV, but she reacts to phone calls mostly due to me being on them; she literally starts meowing and running over when the

One of my cats cat never reacts to the TV, but she reacts to phone calls mostly due to me being on them; she literally starts meowing and running over when the phone just from the sound of the ringback tone (the pulse when I call someone and am waiting for them to pick up, not sure if I'm using the correct word). From what I can tell, she doesn't really understand there's a person talking to me from the phone; she doesn't react at all to anything the other person says or even indicate that she notices it at all. I think she just gets excited when she knows I'll be talking a lot because she's very interactive. When I first adopted her a couple of years ago, she was very clingy at first, and after a couple of weeks developed a (thankfully short-lived) habit where she would start trying to attack my hands whenever I was on the phone or a work video call, so I think this is just the more toned down version of that excitement. My other cat will react very strongly to seemingly arbitrary sounds regardless of the source (TV, outside, a person in the room) and also seem not to be able to tell where the sound is coming from. He'll get wide eyed and start looking around randomly trying to identify the source, but often completely in the wrong direction (e.g. at me or the other cat instead of the TV). Some of the sounds he's reacted like this to are a hunting horn sound from TV, someone's stomach growling when he was on their lap, or me singing in falsetto. My partner and I suspect that he reacts like this when he thinks something sounds like an animal and then looks around to try to find where it's hiding, but there's no way for us to verify this.