Are the audio tours connected to headphones by Bluetooth? Does a person who wears hearing aids need over-ear headphones, or can he connect to the audio information through his Bluetooth hearing aids? What about bone conducting headphones?
The tours I've taken have used "whisper" sets where you carry a little box on a lanyard and use a wired earbud to hear the guide. The sets are given out before the first walking tour and collected after the last one. I wear hearing aids and I've tried over-ear headphones, which are too heavy and bulky for me, and removing one hearing aid for the tour, which is risky. I've used a device like this, with a D-shaped loop to hold in place and no need to insert in the ear. It works OK if it fits, but I've been through several till I got the right fit. Never seen Bluetooth used this way on a tour.
The foolproof solution would be wired headphones, but they take up space, can be delicate, and cost more than earbuds.