All new recorded dialogue for this event (and the rest of the update) suffer from poor audio quality issues in the EN dub.
Whenever characters are yelling, screaming, or otherwise speaking loudly there's a very noticeable scratchy static sound that affects these high volume lines.
This isn't just contained to an event we're going to move on from in a week, this even affects the voiced treasure scenes such as Tove when she has loud lines, other treasures may be affected as well. The worst offender by far is Summer Elegg's burst, which you're going to be hearing all the time with all this scratchy artifacting. If you go back and listen to the previews for Summer Elegg you'll notice this issue is present in those videos as well, which means it's not a game problem.
Either there was something that went wrong with processing the EN dub's audio and they somehow didn't notice it, or the recordings were done with a fucked up mic/improper settings and they had no choice but to ship it like this. Whatever it may be, the incompetence to let this happen is astounding.

I realize this may have been more pertinent to bring up in the first days of the event but I've barely felt like engaging with the game lately due to the writing, treasure batches, and fanservice going downhill. To my surprise I've only seen one complaint over the past few weeks about this issue, but I suspect others thought they weren't hearing things right or just crazy.
This is just a small sample of affected lines, there are dozens of examples I could have pointed out.
https://files.catbox.moe/q2cts5.mp4