How do you remove echo in the hall?

An echo is the reflection of soundwaves coming back at you. In order to remove the echo you need to absorb the sound instead of allowing it to bounce back. If this is a simple in-home hallway then you might simply hang a decorative quilt or rug on the hallway walls, or put down a runner rug on the floor if the floor is hard material. If it is a much bigger hall like in a school or church then your best bet is to put down carpeting or pursue sound absorbing ceiling tiles and wall tiles. Also placement of the absorptive material is key and might take some trial and error to get the best results.