The best type of room for deaf people
Most people with hearing problems, given the choice, would like to be in a room which, first and foremost, doesn't echo. If you have normal hearing, you will probably assume that no rooms echo, and of course you are right to the extent that you don't hear your exact words coming back at you. However, room surfaces reflect sound and they do so out of step with one another. This causes interference and distorts the sound that the deaf person is trying to understand.
Sound reflects from hard surfaces and is absorbed by soft ones. So do what you can to eliminate hard surfaces where feasible. Ideally this means a carpeted room, full curtains and upholstered chairs, etc. Never have rigid frame chairs on a bare floor and expect anyone with a hearing problem to put up with the noise of them being dragged around. This can be extremely painful.
If you are catering for a large number of deaf people, obviously the seating should be as close as possible to whoever is going to address them. This means that a square room is preferable a long thin one. You may wonder about setting up a loudspeaker system, but this needs care. Loudspeakers can distort if they are not good quality and properly set up, and at high volumes they can be painful. So you will need to do trials first, but never, never leave the trials until all the deaf people are in the room. Finally, if you have a good budget, a loop system may be appropriate to facilitate use of hearing aids.
Disclaimer: The information on this site is for a lay audience and I cannot be responsible for errors or omissions. The views, strategies, advice and suggestions etc are based on my personal experience and are not necessarily appropriate for anyone else. They should, hopefully, stimulate individuals to develop their own strategies.