Sounds are not letters
Phonetics is the study of speech sounds: how we make them, how they travel and how we hear them. A letter is a mark on paper. A sound is what you say. They do not always match: knife has five letters but three sounds, because k is silent. Phone starts with the two letters ph but one sound, f.
Every speech sound is made by air coming from the lungs, passing the voice box (larynx) in the throat, and being shaped by the tongue, teeth and lips.
Vowels: free air
A vowel is a sound made with free air: nothing touches or blocks it. We tell vowels apart by three things:
- Height of the tongue: high (ee, oo) or low (aa).
- Front or back: ee is front, oo is back.
- Lips: rounded (oo) or spread (ee).
A language can have more vowel sounds than vowel letters. English has five vowel letters (a, e, i, o, u) but around twenty vowel sounds.
Consonants: blocked air
A consonant is made when the air is blocked or squeezed somewhere. We describe each consonant in three ways:
- Voice: voiced (the throat buzzes: b, d, g, z) or voiceless (no buzz: p, t, k, s).
- Place: where the gate is: lips (p, b), tongue tip (t, d), back of tongue (k, g).
- Manner: how the gate works: closing fully and bursting (p, t, k), squeezing to hiss (s, f), or sending air through the nose (m, n).
Test: put a finger on your throat and say zzz and then sss. You feel the buzz only in zzz.
Sound and phoneme; variants
A phoneme is the smallest sound unit that can change the meaning of a word. Swap p for b in pin and you get bin, a new word. So /p/ and /b/ are two phonemes.
One phoneme can be spoken in slightly different ways. The p in pin comes with a small puff of air; the p in spin does not. A listener hears the same /p/ both times. These are variants of the same phoneme. They never make a new word, and they usually depend on the neighbouring sounds.
Assimilation, dissimilation and simplification
In real speech, sounds next to each other change.
- Assimilation: a sound becomes more like its neighbour. Input is said as 'imput' because n moves to the lips to match p. It can also be about voice: in many languages a voiced consonant turns voiceless before a voiceless one.
- Dissimilation: two similar sounds become less alike so speech is easier. Many people say Feb-u-ary, dropping one of the two r sounds.
- Simplification: a hard group of consonants loses one. We say lisen for listen and hansom for handsome.
The reason is always the same: the mouth looks for the easiest path.
Historical alternations
Sometimes a sound changes inside one word family because of old rules that no longer feel natural. These are alternations. English: knife and knives (f and v), foot and feet (oo and ee), sing, sang, sung. Many languages, including Slavic and Indian ones, have such pairs: a root keeps its meaning but a vowel or consonant swaps when the word takes a new ending. Learn them as patterns, not as exceptions.
Euphony: the music of sounds
Euphony means a pleasant, smooth sound. Writers use sound on purpose:
- Alliteration: the same starting sound repeated ('slowly the sea slips by').
- Assonance: the same vowel repeated ('the moon in June').
- Onomatopoeia: words that copy a sound (buzz, splash, कल-कल).
Harsh sounds (k, t, r) can show anger or speed; soft sounds (m, l, s) can show calm. Writers also avoid ugly clusters of consonants so the line is easy to say. The opposite of euphony is cacophony.
Try it
Throat test: hold your throat and say p-b, t-d, k-g, s-z. Which of each pair buzzes? Speed test: say 'ten bikes' slowly and then fast. Where does your tongue go? Write down three words you say differently in fast speech.
Key formulas and definitions
- Vowel = free air; consonant = blocked or squeezed air
- Voiced = throat buzzes (b, d, g, z); voiceless = no buzz (p, t, k, s)
- Consonant description = voice + place + manner
- Phoneme: changes meaning (pin / bin); variants: do not change meaning
- Assimilation = neighbours become alike; dissimilation = alike sounds drift apart; simplification = a sound drops
Worked examples
1. Describe the consonant b in 'bat'.
Voice: voiced (the throat buzzes). Place: lips (both lips close). Manner: stop (the air is blocked completely and then bursts out). So b is a voiced lip stop. Its voiceless partner is p.
2. Are the p in 'pin' and the p in 'spin' two phonemes?
No. They sound a little different (puff or no puff) but swapping one for the other never gives a new word. They are two variants of one phoneme /p/. Compare pin and bin: p and b are different phonemes because the word changes.
3. Why do many people say 'tem bikes' for 'ten bikes'?
Assimilation. The sound b is made with the lips. The tongue tip n comes right before it, so in fast speech n moves to the lips and becomes m, the lip nasal. The sounds become more alike, which saves effort.
4. Name the sound change in 'castle' being said as 'kassle'.
Simplification. In the group s-t-l the middle sound t is dropped because three consonants in a row are hard to say. The letter t stays in the spelling, but it is no longer pronounced.
5. Read the line 'The sea slowly slips by, soft and still'. Which sound device is it and what mood does it give?
Alliteration of s (and soft l and m sounds). It sounds like a smooth hiss, so it gives a calm, gentle mood. This is euphony.
Common mistakes
- Counting letters as sounds. 'Knife' has five letters but three sounds; 'phone' has two letters ph for one sound.
- Saying vowels are the letters a, e, i, o, u. A vowel is a sound made with free air; some languages and words use letters like y or w as vowel sounds.
- Calling every different-sounding p a new phoneme. Only a difference that changes meaning makes a new phoneme.
- Thinking assimilation and dissimilation are the same. In assimilation neighbours become alike; in dissimilation they become less alike.