Hi
All I did with mine was buy some mp3 players from eBay, they were about 99p from China, then searched YouTube for ambient factory sounds,there are loads each many hours long, so no looping needed, I recorded the sounds on my PC, wrote them to a number of memory cards, the with the cards in each player I can select which ones or combination if I want more than one sound.
So I can have country sounds at one end, factory sounds at the other and train station sounds in the middle, if I wanted to.
This is the sort I got, other types are available;) https://www.ebay.co.uk/itm/F343-TF-card-U-disk-MP3-Format-decoder-board-amplifier-decoding-audio-Player-mod/192638831210?epid=2291424163&hash=item2cda2b4a6a:g:NVUAAOSwlUhbg3E6