I have 2...they both make a cash register sound......hmm I'm aiming the holes on the open space just past the posts (one hole open on each side). Guess I'll have to aim more on the posts. That seems to work!
Thanks!
I recall that CH said to aim 15 degrees off the post. But I thought that couldn't be right because I'd be blocking the airflow partially. So I went about 30 deg off the posts and that caused an annoying whistle. Didn't experiment enough because that cap is so tight!