Never been to Pennhurst myself but I've done plenty of tunnel investigations over here in Derbyshire - old mine workings, underground passages near some of the old estates. The acoustics in confined underground spaces do something weird to your perception, you start hearing things that probably aren't there, or maybe are, hard to say.
What bothers me about a lot of these American asylum locations is how much of the activity gets contaminated by the sheer number of people who've been through them on ghost tours. Too much noise, too many people expecting something. You cant get a clean baseline reading.
Has anyone actually done a proper solo overnight in the tunnels rather than a group thing? Genuinely curious whether theres consistent activity or just the usual stuff that gets amplified by group hysteria. If anyone's got raw footage or EVP recordings from a solo session I'd actually bother watching them. Most of the Pennhurst stuff on YouTube is just lads screaming at each other in the dark.