I would think the same way as it does for stories - the piece has to have high enough rating, 4.5 and above given that there is enough people that rated the work.
I thought the same thing until one of my audios got a "Hot" pretty early-on with no real tell-tale signs of why (other than the thought of the moderator really enjoyed it! Lol)
You piqued my interest but my research has left me confused.
If this is you https://www.literotica.com/authors/Lonely50M/works/audio
You have 10 audio stories out there and one of them shows the Red 'H', which as AnnieLit points out comes when you are at a score of 4.5 of higher.
However, 8 of your 10 stories are 4.5 or higher, so you theoretically could have 8 red 'H's.
AnnieLit also raised the point of whether enough people have rated your work for it to qualify. I don't know what that threshold is and can't see your number of votes, only views (or listens, in this case).
For my own catalog, I see that the lowest number of votes I have on one of my Hot stories is 25. Take a look at your Works and see how many votes you have for each story. If it's more than 25 and higher than 4.5 and doesn't have a red 'H', then you're on your own as far as contacting admin. good luck.
Wow, I really appreciate that. Yes, that's me. Thank you so much! I'm kind of new to this and was just wondering. It really doesn't make a difference to me. Its definitely not a priority.