Just spotted these on ebay (no connection):

https://www.ebay.co.uk/sch/Caving-Potholing/123469/m.html?item=311884504887&_ssn=locheed

Those look fantastic.  It's great that they are identified with such scholarly accuracy eg "Small stream running through field, Mendip Hills, 1970".
One pictures a room full of bearded pipe-smoking ancients listening to the recording arguing about exactly which stream it was.
It could start a whole new theme for 'Wezzit'  - "Identify the cave and location from this sound clip - a popular Dales trip in moderate flood conditions...."