Feel it, then say it π€π³π€
Hold your phone and tap each word. Voiced sounds buzz β that is your voice-box vibrating; voiceless sounds stay still. Then take your turn: say the buzzing word, and the phone listens to check you voiced it. Feel β say β the phone measures. All on your phone; nothing leaves it.
Tip: put your fingers on your throat and say βzzzβ then βsssβ β you feel the buzz start and stop. Your phone does the same.