There are 26 letters in the English alphabet, but there are 39 sounds (15 vowel sounds and 24 consonant sounds) prooduced by these letters.
A vowel is a sound where air coming from the lungs is not bloecked by the mouth or throat. All normal English words contain at least one vowel.
The vowels are:
 A, E, I, O, U, and sometimes Y. 
 ‘Y’ can also behave as aa consonant when it is at the beginning of a word.
A consonant is a sound formed by stopping the air flowing through the mouth.
The consonants are:
B, C, D, F, G, H, J, K, L, M, N, P, Q, R, S, T, V, W, X, Y, Z
Alll the sounds produced in the English are either voiced or voiceless. Voiced sounds occur when the vocal cords vibrate when the sound is produced. There is no vocal cord vibration when producing voiceless sounds. To test thise, place your finger tips hand on your throat as you say the sounds. When saying the voiced sounds, you should be able to feel a vibration. When saying the voiceless sounds you sound not be able to feel a vibration.
Sometimes it is very difficult to feel the difference between a voiced and voiceless sound. Another test may help. Put a piece of paper in front of your mouth when saying the sounds- the paper will should move when saying the unvoiced sounds.
All vowels in English are voiced. Some of the consonant sounds are voiced and some are voiceless. Some of the consonanat sounds produced in English are very similar. Many times the difference between them is because one is voiced and the other is voiceless. Two examples are ‘z’, which is voiced and ‘s’, which is voiceless. See the chart below for a listing of the voiced and voicelless consonants.   
 Voiced consonants            Voiceless consonant
             b                                               p
             d                                               t
             g                                               k
             v                                               f
             z                                               s
             th                                             th 
             sz                                             sh
             j                                                ch
             l                                                 h
             m
             n 
             ng
             r
             w
             y
Any consonant sounds come in pairs. For example, P and B are produced in the same place in the mouth with the tongue in the same position. The only difference is that P is an unvoiceds sound (no vibration of the vocal cords) while B is a voiced sound (vocal cords vibrate). Put your hand on your throat as you say the pairs below to feel the difference.
Note tht the first pair of consonants in the table (p, b) is produced at the front of the mouth. Each pair shifts further back with the last pair (k, g) being produced at the back of the mouth.
The following consonant sounds are represented using the International Phonetic Alphabet(IPA). The words in parentheses represent phonetic transcriptions. we can clearly distinguish (b, d, g) from (p, t, k) spoken by native US/UK English speakers. People can clearly distinguish my (b, d, g) from (p, t, k) too. the only perceivable difference between the two groups is that a puff of air comes out when we say (p, t, k).
Certain pairs of consonants can be problematic for some learners. In some cases, the main difference between the pair is whether the consonant is voiced or unvoiced, that is, whether or not the vocal chords vibrate when making this sound.
This discovery activity can be used to help learners notice the difference between voiced and unvoiced consonants. Begin by asking learners what noise a bee makes. As they make a buzzing noise, do the same and purt your fingers on your throat, indicating that they should do likeewise. This will allow them to feel the vibrations of the vocal chords that occur with voiced consonant sounds. Ask them if they can feel the vibrations.

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Then focus on a voiced / unvoiced pair such as s and z. Make the sounds with your fingers on your throaet, indicating that the learners should do the same. You can help learners with this by getting them to make the ‘bee’ sounds for z, and the sound a snake is supposed to make for s. Ask them when they feel the vocal chords vibrate – with s or z? (The answer should be z). Tell them that this is the main difference between the two sounds, and that z is voiced while s is unvoiced. You could then give them a list of words and ask them to categorise the underlined consonant sound into these two categories. With /s/ and /z/, you might choose to include some third person singular verb and plural endings. Inn this list the sound being focused on is the final sound in each case.
/s/
/z/
cupss
pens
speaks
reads
gets
goes
puts
lives
tents
cars
plants
sees
baggs
hears
looks
learns
stops
rise
rice
rose
place
plays
Learners then use the chart to deside which of the other consonant sounds are voiced and which are unvoiced. In a computer lab, learners could do this in pairs. They listen to a sound and repeat it, with their fingers on their throat to check ifz it is voiced or unvoiced. In class with the IWB, or a computer and a projector, the teacher or a learner could click on sounds while the rest of the class repeat them and categorize them into voiced or unvoiced.
As a follow up, you could do a minimal pairs activity using some voiced / unvoiced pairs, focusing on initial consonannt sounds. Display this list or something similar on the board and say a word from each pair. After each word learners have to say voiced or unvoiced, depending on which of the pair they hear. They can then test each other in pairs.
Voiced
Unvoiced
Ben
pen
do
to
gone
con
van
fan
gin
chin
zoo
Sue
This activity has the advantage of establishing the voiced / unvoiced distinction, and a shared gesture that learners and the teacher can use in class to indicate that a sound is voiced or unvoiced, i.e. the fingers on the throat. It also helps learners to become conscious of the muscle movements involved in voicing a consonant. All of this will be useful in future classes if problem arise in the discrimination or production of voiced / unvoiced consonant pairs.
what is Voiced?
A simple explanation of voiced consonants is that they use the voice. This is easy to test by putting your finger on your throat. If you feel a vibration the consonant is voiced. Here is a list of some voiced consonants. Pronounce each consonant sound (not the letter) and feel the vibration of your vocal chords.
b
d
th (as in then)
v
l
r
z
j (as in Jane)
What is Voiceless?
Voiceless consonants do not use the voice. They are percussive and use hard sounds. Once again, you can test if a consonant is voiceless by putting your finger on your throats. You will feel no vibration in your throat, just a short explosion of air as you pronounce. Pronounce each of these consonant sounds and feel NO vibration in your throat.
p
t
k
s
sh
ch
th (as in thing)
Careful! Some Consonants Voiced, but are Voiceless
When consonants are put in groups they can change the voiced or voiceless quality of the consonant that follows. A great example of this is the past simple form of regular verbs. As you know, regular verbs add -ed to the end of the verb in the past simple.
play – played
wash – washed
live – lived etc.
These past simple verbs all end in ‘-ed’. However, some of the verbs are pronounced with a voiceless ‘t’ sound and some are pronounced with the voiced ‘d’ sound. Why? Here are the rules:
If -ed is preceded by a voiceless consonant sound (p, k, sh, etc.) -ed sounds as a voiceless ‘t’. Remember that the ‘e’ is silent.
If -ed is preceded by a voiced consonant sound (d, b, v, etc.) -ed sounds as a voiced ‘d’. Remember that the ‘e’ is silent.
If -ed is preceded by a vowel sound (often ‘ay’) -ed sounds as a voiced ‘d’ because vowels are always voiced. Remember that the ‘e’ is silent.
Exception: If -ed is preceded by ‘t’ pronounce a voiced -id. In this case, the ‘e’ is pronounced.
This pattern can also be found with plural forms. If the consonant preceding the ‘s’ is voiced, ‘s’ will sound as voiced ‘z’:
chairs
machines
bags
If the consonant preceding the ‘s’ is voiceless, ‘s’ will sound as voiceless ‘s’:
bats
parks
pipes
Connected Speech
Finally, when speaking in sentences the ending consonant sounds can change based on the following words. This is often referred to as ‘connected speech’. Here is an example of a change from a voiced ‘b’ in the word ‘club’ to a voiceless ‘p’ because of the voiced ‘t’ of ‘to’ of the following word:
We went to the club to meet some friends.
Here is an example of a change from a voiced ‘d’ past simple verb changed to voiceless ‘t’:
We played tennis yesterday afternoon.
All sounds in the English language have a sound associated with it.  The voiced “noise” that you hear if you say sounds individually, originates from the vibration of the vocal cords and the way in which you shape your tongue and lips and palate to create the consonant.  When you use your vocal cords to make a consonant, you are producing a voiced consonant or vowel.
But there are a handful of voiceless consonants that are produced without vibrating the vocal cords at all.  The “noise” that you hear, originates somewhere in the mouth or at the lips.  It is easier to memorize which consonants are voiceless since there are fewer of them-only nine:
/p,
t,
k,
s,
sh,
ch,
h,
f,
th/ 
Try to make each of these sounds individually.  You should not be voicing at all.  The /p/ sound will have its noise made at the lips.  The /t/ is made by placing the tongue behind the upper teeth and pushing/stopping air rapidly. The /k/ is made in the back of the throat with the tongue pushing against the palate.
Of these sounds (except for /h/) there are partner sounds or minimal pairs that are made exactly the same except voicing is added.  Compare the following pairs of sounds:
/p/ vs. /b/
/t/ vs. /d/
/k/ vs. /g/
To feel vibration, place your fingers on your larynx, the bony structure of the front part of your neck, and say, “ah.”  Do you feel some vibration? Now make the first sound in each of the above pairs.  Again, place your fingers on your larynx.  You should not feel vibration. If you feel vibration you are not pronouncing the sound correctly.  Only the second sound in each pair should have a vocal cord vibration.
When sounds that are voiced are produced without voice, word meaning changes drastically. For example, “pill” sounds like “bill,” “tan” sounds like “Dan,” “Kate” sounds like “gate.”  Miscommunications are inevitable! Why is this important?  You will need to understand the voicing aspect of final consonants on words to help you understand past tense endings and plurals endings. 
A voiced sound is one in which the vocal cords vibrate, and a voiceless sound is one in which they do not. Voicing is the difference between pairs of sounds such as [s] and [z] in English. If one places the fingers on the voice box (ie the location of the Adam’s apple in the upper throat), one can feel a vibration when one pronounces zzzz, but not when one pronounces ssss. (For a more detailed, technical explanation, see modal voice and phonation.)
In European languages such as English, vowels and other sonorants (consonants such as m, n, l, and r) are modally voiced. In most European languages, other consonants contrast between voiced and unvoiced sounds such as [s] and [z], though in English many of these are at least partially devoiced in most environments.