Turning Off Ambient Sound

[AGP]

As weird as this title might strike you, I've been having the oddest problem.

Tesseract has been such a help to me, but sadly we have both been stumped on this.

In the map there are various ambient sounds set up to play, and for reaching the end of the map, I'd like it to go quiet, as it ends with some narration.

However, we've gone about several different ways of trying to silence it, but nothing has worked, and due to the complexity of the scripting (aka messiness of the hps file) I can't really post just the sound sections, so I've instead attached the whole hps file.

https://www.dropbox.com/s/646u1ng8i67edx...4.hps?dl=0

Thank you in advance for your help. <3