Cách phát âm /f/ và /v/

Oh, that's a quiet one, isn't it? No breath stream escaping, feel a gentle, smooth, airless sensation. Now, sustain the F in these words. Knife, leaf, half, finger, elephant. Laugh, off, telephone, fire, roof. Sustain the F in these sentences. I used a knife to cut the leaf in half. When she touched her finger to the elephant, I had to laugh. I got off the telephone fast when I saw the fire on the roof. The V, cognate F. This is voiced, fricative labiodental. Upper teeth to lower lip. Feel the teeth planted right in the lower lip. You set the lower lip vibrating, that's what makes the sound. You'll feel a gentle, dark, buzzing vibration on the lower lip. All suggestion of the F must be out of there, otherwise your V sounds like an F. Good. Now, sustain the V in these words. Five, of, seven, sleeve, very. Leave, river, drive, move, stove. Sustain the V in these sentences. Play it for full musical value. Five, of, seven, sleeves, are very long. Did they leave the river for a drive? Let's move the stove last.