Plosives – a plosive is a consonant characterized by a complete obstruction of the outgoing airstream by the articulators, a build up of air pressure in the mouth, and finally a release of that pressure. A stop is merely the first part of this sound (the stopping of the airstream). In other words, in producing these sounds, the air is stopped for a brief moment (say pop over and over and pay attention to what’s happening). There are three types of plosive in English. For an interactive example of each sound (including descriptive animation and video), click this link, then in the window that opens, click stops, and select the appropriate sound.
/p/ /b/ bilabial plosives
A bilabial (from bi- two and labia lip) plosive is a sound in which the flow of air out of the body is interrupted by closing the lips together. English has two bilabial plosives — /p/ in which the vocal chords are not used (voiceless) as in pizza and pepper, and /b/ in which they are used as in boy and trouble.
/t/ /d/ lingua-alveolar plosives
A lingua-alveolar (from lingua tongue and alveola the ridge just behind the front upper teeth) plosive is a sound in which the flow of air out of the body is interrupted by touching the tongue to the alveolar ridge — the part of the roof of the mouth, just behind the upper front teeth. English has two lingua-alveolar plosives — voiceless /t/ as in top and must, and /d/ which is voiced as in dog and troubled.
/k/ /g/ lingua-velar plosives
A lingua-velar (from lingua tongue and velar the velum or soft palate) plosive is a sound in which the flow of air out of the body is interrupted by touching the back of the tongue to the velum — the soft part of the roof of the mouth farthest from the front teeth; it’s about as far back in the mouth as can be reached with the tip of the tongue. English has two lingua-velar plosives — voiceless /k/ as in cook and ask, and /g/ which is voiced as in dog and good.
Aspiration – aspiration refers to the release of air at the end of a consonant sound. Plosives are naturally aspirated (because air is released following the stop portion of the sound. Linguists often use the term aspiration only to refer to strong puffs of voiceless air after a plosive. Sometimes the term “aspirated stop” is employed, but this is a misnomer as stops cannot be aspirated (aspirated stops thus being plosives). Regardless of aspiration though, the procedures for producing sounds are the same, thus ‘aspirated /p/ is not annotated differently from non-aspirated /p/.