Voiced & Voiceless 

If vocal cords vibrate in the throat, uttering a sound, we have a voiced sound, and if vocal cords do not, the sound is unvoiced. All the vowels produced in English are voiced, while consonants are either voiced or voiceless.

Learning how to differentiate voiced from voiceless sounds is helpful because
1. It helps us label a consonant as voiced or unvoiced sound.
2. It also helps determine whether “s” at the end of a word makes the /s/ sound or the /z/ sound.

If you put your hand on your larynx while pronouncing a sound, you notice that your vocal cords vibrate for voiced sounds and they do not vibrate in unvoiced sounds.

Vowels in English are A, E, I, O, U. All of them have voiced sounds because their pronouncing requires the flowing air in the larynx.

These consonants produce voiced sounds: B, D, G, J, L, M, N, R, V, W, Y, and Z.

These consonants produce voiceless sounds: P, T, K, CH, and F.

Here is the table of voiced/voiceless consonant sounds:

There is only one consonant that can be either voiced or unvoiced and that is the ending ‘s.’
Depending on what consonant precedes it, it can be voiced or unvoiced.

a. If it follows a voiced consonant/vowel, it becomes voiced and sounds /z/:

b. If the ending 's' follows an unvoiced consonant, it becomes unvoiced and sounds /s/:

Digraphs are sounds that are made up of a combination of two letters, one is always voiced and the other is unvoiced. But, the digraph 'th' is made up of two unvoiced sounds: 't' and 'h'.
The interesting point is that 'th' can produce either voiced or unvoiced sound. If it produced /ð/ sound, it is voiced, and if it produces /θ/ sound, it is unvoiced.