You can try other attention draws instead of yelling.
My littles all turn around concerned when I stop humming....
I just recently realized I do it all day...
You could try:
1. Flashing lights on and off.
2. Coaches Whistle.
3. Waving Red Flag/Green Flag.
4. "Catch a Bubble" technique.
5. The standard "One, Two, Three".
6. A flashing light wand. ($2)
I am sure there are more, those are just some I have used at one time or another.
