Many pronunciation problems can be solved by learning about voiced and unvoiced sounds.
Voiced sounds use your vocal chords, unvoiced sounds don’t. All vowels in English are voiced. Unvoiced sounds are not very loud. If you put your hand against your throat while talking, you’ll feel the vibrations from your vocal chords when you’re saying voiced sounds, but you’ll feel no vibrations when saying unvoiced sounds. When you whisper, the sound you make is unvoiced.
The difference between the Z and S sounds is that the Z is voiced, the S is unvoiced. (In written English, sometimes the S makes the S sound, and sometimes it makes the Z sound.) Here are some examples:
zip, sip, zoo, sue, razor, racer, rays, race, phase, face
Similarly, the main difference between the D and T in English is that the D is voiced, the T is unvoiced:
drip, trip, dry, try, fried, fright, feed, feet, seed, seat
Often students make mistakes if a word ends in a voiced sound. For example, if a word ends in D, the D should not be pronounced like a T; a D at the end of a word should be pronounced the same as a D at the beginning or in the middle of a word.
Here are more pairs of letters where the main, or only, difference is that one is voiced and the other is unvoiced:
B, voiced, P, unvoiced
blob, plop, beer, peer, back, pack, robe, rope, mob, mop
G, voiced, K, unvoiced
grab, crab, god, cod, mug, muck, lug, luck, rag, rack
V, voiced, F, unvoiced
view, few, vine, fine, invest, infest, save, safe, wave, waif
J,voiced, CH, unvoiced
gin, chin, jive, chive, jello, cello, edge, etch, ridge, rich, badge, batch
TH: th is used for two sounds, one that is voiced, and one that is unvoiced.
Some examples of words with voiced TH: this, that, other, the, and bathe
Some examples of words with unvoiced TH: theory, thorn, with, month, and bath