Phonemes and Allophones
When linguists study the sounds of a language they observe how the sounds are made and classify them as vowels, consonants, etc. They also study how those sounds correlate with words that have different meanings. They do this by finding pairs of words that differ by a single sound (through listening, not reading). If there are at least two such pairs of words with a different meaning for each member of the pair, then it is assumed that the variation is used to distinguish meanings of words in the language. You might expect that sounds that are very different from each other, for example p, k and t, would be used to form words with distinct meanings. There are phonological rules that affect the pronunciation of single, individual phones.
Stool
Eat
Cop
School axe Pop
Spool
Leap
Under this transcription:
All the words in the 1st column share a sound: [t]
All the words in the 2nd column share a sound: [k]
All the words in the 3rd column share a sound: [p]
Problem with (t): The actual ‘t’-sounds in the 1st column are a bit different from each other.
Put your hand in front of your mouth and say “top”.
There’s a strong burst of air when you say the “t”.
This burst isn’t there when you say “stool” and “eat”.
Problem with (k): The actual ‘k’-sounds in the 2nd column are a bit different from each other.
Put your hand in front of your mouth and say “cop”.
There’s a strong burst of air when you say the “k”.
This burst isn’t there with “school” and “axe”.
Problem with (p): The actual ‘p’-sounds in the 3rd column are a bit different from each other.
Put your hand in front of your mouth and say “pop”.
There’s a strong burst of air when you say the “p”.
This burst isn’t there when you say “spool” and “leap”.
Solution: On closer inspection of the sound of p or t in the above words, linguists have observed that actually there are two sounds for the p and two sounds for the t. For the following words a small puff of air occurs when