This can be a bit confusing, because there are both tapes and radios in the game. The tapes do
not count for this achievement. The radios are what have the interviews. There's four in total:
1. The hall with the janitor has a flight of steps, on the third floor, dangling from wires.
2. The bathroom connected to room 110. Flush the toilet for it to appear.
3. The room marked 020, in the basement.
4.
Note that you need to actually interact with them for the achievement, finding them isn't enough. This video will help as a visual guide.
EDIT: There have been comments about the last radio not spawning. I would recommend reading below if anyone is having this issue. Multiple people have noted that reloading the game may help.