Herbi overflow making noise

[kien]

Looking at those pictures, it doesn't seem to me like you have a heck of a lot of room to play with between the main herbie drain and the backup/emergency drain. Normally you want some distance between the two so that the water level in your overflow box is well above the main drain and well below the emergency drain. It looks to me like you only have like an inch(ish) between the two drains? That will be (or is) hard to adjust to get it perfect, and even if you get it perfectly aligned between the two pipes it won't take much to knock the water level/flow to the point where it is hitting the emergency drain or the main drain. I suggest lowering your main drain down to at least half the height that it currently is now. That should help as it'll give you more room to play with the herbie level.