The most annoying sound in the world

Do you know how incredibly talented my children are? They have the capability to take any simple sound (let's just say for the sake of example the sound of the letter "I") and turn it into the most annoying sound in the world.

One of them begins by saying it on repeat over and over and over again in varying pitches and tones , 'I...i...I...i...I...i..." Usually at first I tune her out because I am distracted- I may be driving or on the phone- but then the other one notices the new game and they both start in- harmoniously(ish) making the same sound over and over until my head explodes. All I can do is give them the evil eye and say, "You have got to be kidding me!!!!"

Then they just laugh. And this is how I end up getting through the evening...

PS What "special" talents do your children have???