I think the falling off the level aah/eep noise is loud, so that can probably be turned down too? Also, something that just occurred to me, and, unless it's already been done and I somehow missed it, that is do you think there should be different sounds for, say, female lemmings like Lemminas and Millas, against the default sounds for male lemmings? Like maybe for assigning the bomber to a Lemmina it can use a more feminine voice saying "oh no" for example. Similarly, probably there might be a more feminine ahh/eep sound for Lemminas falling off the level vs the default "die" sound file. This would definitely give them a distinct personality based on gender. Then again, I think the same could probably be done with changing the sounds of the various ethnic lemming sprites, like the ones Strato came up with, but well, that's probably best left to the creator of the sprites. At the same time, I don't know if this would cause problems with maybe overriding sound files, but then again that's why it's always recommended to back up the sound folder of your NL directory.
As for some of the ones that you listed as "unknown" in the OP, here they are:
thunk - Some traps use this sound, such as the evil flower trap from the Highland tileset of L2, the armor reaper trap with a vertical axe and it comes down at a right angle to kill a lemming from Dexter's Halloween tileset, the spikes trap from the Renaissance tileset, etc.
ting - This is just the sound for the final 3 bricks of a platformer/builder