What...one term for all these three images? That's hard...
I also love Unsplash, especially when it comes to the resources for presentations! Just input some search terms and you'll get nice backgrounds for everything, lol.
For my guess...eh...
Light, noise, sounds?
Idk, it's just some random guesses...
The answer and the next round of "Guess the Word" can be found here:
https://steemit.com/contest/@bengy/guess-the-word-37