I know that audio guides are a good way to control visitor flow and visit times, ensuring people get an overview while also pushing them through sites at a suitable speed. They can provide a reliable service not always possible unless you employ a large pool of highly trained staff, such as language options, BSL on video screens, child friendly tours. They can be a flexible tool, such as at Apsley House, offering visitors a choice of tours depending on their specific interests. They allow historical venues to be free from obtrusive signs. From the visitor's point of view, their experience can also be enhanced by a good audio guide, with music, interviews from behind the scenes staff, and video clips.
However, using so many audio guides in a short time highlighted two - to me - unpleasant side effects. The first is how much people were attuned only to the audio guide, to the detriment of all else. The second was the isolation of the user.
For example: Westminster Abbey is full of fascinating insights into history, religious changes, societal commentary, fantastic sculpture... but woe betide anything not deemed worthy of the 20 or so stopping points. For most visitors, the audio guide was king, and nothing else worth looking at. If you did noticed the wonderfully and amusingly carved wooden seats, tough. The audio guide cares not, and there's no other information available unless you are willing to find, flag down and ask a human (lovely misericords by the by) Gradually you loose interest in anything not on the guide, as information isn't fed to you, and therefore, the thing to interest you may not be "important".
It's worth saying that not all visitors became audio-zombies, as some people were content to ignore the audio guide wholly and just look around for themselves.Or they were engaging with their children, who weren't patient enough to use the audio guides. In two of the four venues I visited, the only source of readily available and detailed information was the audio guide though, so it's hard to say how their exploration was altered by the lack of context. They saw, and chose of their own accord what to look at, but how well did they understand and relate without any of the audio guide's overview?
The second side effect of the audio guide was the isolation of users. Interacting with anyone else was clumsy, removing headphones, pausing a handset, you missed part of the tour, or lost your flow in it. Also your audio guide may be slightly ahead or behind of others you are exploring with, so you pause to mention something to them, and they don't get the reference as they haven't had the information yet. You wanted to talk to a companion, but they had just started listening to the extended information.
Eventually people noticeably stopped interacting, beyond sometimes pointing at an object, or passing comment when the guide was paused between stopping points. You experience and engage alone, with rare moments when you briefly discover what other visitors are experiencing, or how they are engaging.
So, the two elements I love about visiting historic venues are the exploration, and the interaction. For me though it feels as though audio guides provide too proscribed a way to engage, and do little to encourage independent exploration or appreciation. "I like that painting, but it's obviously not interesting as it's not in the audio guide, so I'll overlook it". And then being wrapped up in headphones, or holding something to your ear means missing out on personal interaction, the shared moments of enjoyment and observation that may alter your opinion or help you learn about your fellow travelers.
Audio guides can be a fantastic tool, and I assume the tools I recently used are thought to be doing their well job by their venues. I highly commend what has been done with them at Apsley House and the Churchill War Rooms. Yet, I think were I ever to be involved in an audio guide project, I would ensure that the guide actively encourages independent exploration and personal interaction, and that there's easy access to further information beyond the voice in a box.