My in laws, I guess younger older, live with my family so I spend a lot of time around them.
When they are playing videos or talking on their phone, through their hearing aids, I can clearly hear what is playing from as far away as 10-15 feet.
It is something people with bluetooth hearing aids need to know. The other side of the conversation is not as private as they might think. And neither is the sound from whatever they are playing on their phone.
Edited to add:
I can't say that I have found the same for headphones. I don't remember ever sitting next to someone using headphones and hearing quite as clearly what is playing as I do with the hearing aids my in laws both have.