Excellent take on a Null subclass. The use of sonic damage, ranged punches, and reverberating abilities all tie together quite nicely. Throwing the null field at enemies is very clever.

Similarly to others, I have some concerns about Repeat. It's a very cool and thematic ability! But the extended nature of it looks very easy to lose track of and forget in a fight with lots of moving pieces. Might need a rework in a way that's still satisfying without needing the extra bookkeeping. Noticed a handful of punctuation/spacing errors as well. Nothing that's detracting from the score, just a note for when you do another editing pass.

Everything considered, excellent submission. I'll toss this to the Null fan at my table to see what they think of it. 

I think this is a fun new subclass for Nulls, and would probably be easy to dial in/polish with testing and iteration. I think it gets most of the way there in fulfilling the fantasy of playing a hero that doles out sonic damage; however, I would love to see more unique conditions, or perhaps some abilities that grant a "deafened" condition. While I really like the subclass, I don't personally see how it relates to the "One Year of Draw Steel." Really excited to see the subclass get worked on some more - I would love to use it if I play a Null. 

Really fun altogether. It definitely does deliver what's on the tin. The Hulk clap is pretty neat. My gut tells me Repeat! would be a little tedious to use. Moving the null field adds a lot of depth. In that an echo is a repeat of something, it barely fits into the theme.