Cách phát âm /s/ và /z/

Sounds like the kettle's boiling. The S cognate to the Z. Unvoiced S sound, fricative, tongue to gum ridge. The S is like the Z except it's unvoiced, so it's the same tongue placement as the Z. The S is like a gentle escape of steam. Play it softly and smoothly and feel a steady, sharp sensation. Too soft to be a whistle. Now sustain the S on these words. It's, face, this, office, close, police, bus, stops, across, gas. Sustain the S in these sentences. It's a nice face. This office is close to the police station. The bus stops across from the gas station. The Z cognate S. A voiced S sound, fricative. The tongue rim should gently touch the upper gum ridge. The tip in gentle contact with the hard palate. The Z vibrates in that very small open space between the tongue and the upper teeth. Right in here. A little space right between the tip of the tongue and the teeth. It's in that little space that the Z sound is formed. So feel a smooth, strong vibration in the teeth and in the front of the tongue. Now sustain the Z in these words. These, moves, dials, those, gears. Wipers, rains, excuse, is, knows. Sustain the Z in these sentences. Play it for full musical value the first time through. These, moves, turn, the dials. These moves turn the dials. Those gears run the wipers when it rains. Excuse me, is my nose bleeding?