Loop System
The Hearing Loop System is used for people with hearing aids or cochear implants.
The way it works, is it connects to your telecoil, and sends the sound directly to your hearing device.
Many people find this useful, especially in loud areas such as halls, churches, etc. The downside to the Hearing Loop System, is that it blocks out all other noise. Even though it's mostly used for public spaces, it can also be used for smaller spaces. They can be designed so that they don't also spill over to the next room. You may find some in theatres, churches, halls, trains, classrooms, and more.