The voice was not clear for me on 'per un' or 'zio' . 'per un' sounded like 'terra' and 'zio' came out as 'tio'. I listened to it several times as I thought it should be zio but could only hear 't' so presumed I was wrong. But no one else mentions this so maybe I need to get my hearing checked!!
I heard 'Tio' clearly too, but since as far as I could determine their is no such word in Italian, the nearest word that came to mind was 'zio' which made sense. By the way, your comment was marked down by someone. I restored it. I do not understand why anyone should mark down a perfectly reasonable comment. Maybe they think they are better than the rest of us.
The audio is correct. It seems that native speakers of some languages may have a hard time with this. I suggest you listen to the word "tio" in Spanish and Italian (pronounced /tio/ in Spanish , whereas it is pronounced /dzio/ in Italian) using Forvo or Google Translate and you'll realize the difference.