This is one of the big differences between English and many other languages; for example, in Latvian and French the sounds represented by these letters are unaspirated; in other words, they are produced without this puff of air. We can illustrate the difference by comparing how an English word like cuss is pronounced, as compared to the Latvian word kas 'what'. The major difference between these two words is how the first consonant sound is pronounced. If you click on the following example, you will hear the difference:
cuss vs. kas
English people sometimes think that kas sounds like it starts with a [g] sound. It doesn't. Click on the following example, and you will hear the difference:
kas vs. Gus
Although most of the time English [p], [t], and [k] sounds are aspirated (i.e. have the puff of air), there are certain situations in which English speakers produced them without this puff of air. In English, these unaspirated consonants typically occur after an [s] which starts the same syllable. Here are some examples of each type:
|Aspirated consonants||Unaspirated consonants|
You can clearly see the aspiration if you hold a lighted candle, orand this is much safera thin strip of paper vertically in front of your mouth. Hold it fairly close to your lips and say pin. You should see the candle flame flicker, or the strip of paper bend away from your lips.
If you don't see it either (a) you're holding it too far away from your mouth, or (b) you're not a native speaker of English. In the first case, adjust the distance so that the paper (candle) is closer to your lips, and try again. The air which exits from you mouth and bends the paper (or candle) is the puff of air linguists call aspiration.
Try this a few times until you have the paper (or candle) responding with a bend (or flicker) every time. Now, keeping the paper (or candle) at exactly the same distance from your lips, say the word spin. Either the paper won't move at all, or else it will bend much less than it did for pin. This absence of air movement indicates that the sound is unaspirated.
To practise producing an unaspirated [p], [t], or [k] sound, say a word like spin, stem, or skin very slowly. Say it more and more slowly until you consciously register how it feels to say an unaspirated consonant sound. Now say it slowly, but just "think" the [s] and don't actually say it out loud. Constantly check your pronunciation with the strip of paper (or candle) to make sure that you haven't reverted and are still saying an unaspirated sound.
Practise this a few times a day, and in no time you will be saying unaspirated consonants like a pro!