I would like to pass on this very informative bit of info that I learned on another forum. (thank you to Mr V)
If you are an instructor or TKD parent offer this to your students/children as it can prevent a them from making a life changing mistake.
Refer them to the Ninja Mosquito, as it is a sound that kids can hear but adults can not.
The point is adults give advice that kids do not understand because they just don't see the value, just as the adults can not hear the Ninja Mosquito but the kids know it exists because they can hear it.
VALUABLE LESSON: JUST BECAUSE YOU CAN'T SEE, UNDERSTAND, HEAR, OR TOUCH SOMETHING DOES NOT MEAN THAT IT DOES NOT EXIST. MARTIAL ARTS HAS MANY ADVANTAGES THAT THE PARENT and STUDENT CAN NOT SEE, HEAR, OR TOUCH BUT IT EXISTS.
YOUR MARTIAL ARTS INSTRUCTOR IS TRAINED IN ALL ASPECTS OF MARTIAL ARTS. YOUR MARTIAL ARTS INSTRUCTOR BENIFITS THE STUDENT MORE THAN YOU CAN EVER KNOW.
So here is the link to the Ninja Mosquito.
http://www.angelfire.com/ab/vitamin/mrvkempoearsound.html
what about this mosquito? 
LOL 
