Hire sign language interpreters
A sign language interpreter can help an attendee who’s hard-of-hearing, both to understand talks and when chatting in the corridor.
This is similar to real-time captioning – it makes the event more accessible to people who are hard-of-hearing.
Note that these are distinct things: some people can understand sign language but have more difficulty reading; for others the opposite is true.
It’s less useful to a general audience, because most people aren’t fluent in sign language. But if the interpreter stays with a particular person, that allows them to participate in conversations outside the main sessions.
Remember that sign languages vary around the world – for example, British and German Sign Language are as different as English and German. And even the English sign languages differ – British Sign Language and American Sign Language are two separate languages, and mutually incomprehensible. It’s not like British and American English. If you’re running an event in multiple languages, you may want an interpreter for each language.
As with live captioning, it’s helpful to provide the interpreters with a list of specialist/technical terms in advance.
Most events I’ve seen only offer sign language interpreters upon request, but provide live captioning as standard.