Jade's magic relates to soundwaves.
It's actually a shame I didn't write this in her perspective because I constantly entertain the idea of her being able to see soundwaves.

So that explains the "sound"

And then "salvation" is because Pearl literally saved Kira's life, meaning she was Kira's salvation. And Zinnia saved Kira and Jade from their life of pickpocketing and orphanage, therefore also technically the pair's salvation.