Two sounds close enough to trade places: the “th” of think and the “t” of top. Swap one for the other and a different word comes out — this page is how to keep them apart, in both directions.
Do not tap the ridge behind your teeth; slide the tongue tip between your teeth and let the air flow out continuously.
“You stop the air like slamming a door — t! t! No, bello, leave the door open. Tongue between teeth, let the wind blow through!”Nunzio, when he hears it
You cannot hear your own swap. That is the whole problem.
Nunzio records you reading a sentence, scores every sound in it on your phone — nothing is uploaded — and tells you which of these two actually came out. Nunzio — Accent Coach is coming to the App Store and Google Play.