Since different types of sounds link into each other in different ways, it's important to know the categories of sounds. Vowel sounds are created with a relatively open vocal tract. Consonant sounds are divided into the broad categories of "continuous" and "blocked." Continuous consonant sounds are created when the airflow is restricted--but not completely blocked--while passing through the vocal tract. These sounds can be pronounced for an extended time. Blocked consonants occur when the lips or tongue briefly prevent air from passing through the vocal tract.

Vowels

Vowel sounds are difficult to classify. For the purposes of linking, the most important characteristic of vowel sounds is that they are created with vocal tract relatively open and unrestricted. The shape of the mid-line of the tongue (the middle of the tongue from back to front) is the key to creating clear vowel sounds. Subtle changes in tongue shape can create different sounds, and therefore, different words altogether.

All vowel sounds are voiced, meaning the vocal folds vibrate during their production. You can feel this vibration by placing a few fingers on the front of the lower neck while creating the sound.

Continuous Consonants

Continuous consonants are consonant sounds that can be created for an extended period of time. Approximant, fricative, and nasal sounds are all smooth consonants.

Fricatives: the tongue or lips are used to restrict the amount of air passing through the vocal tract. This restriction of air causes friction, or turbulence, as the air passes through.

Fricatives occur in voiced/unvoiced pairs. To feel the difference, place a few fingers on the front of the lower neck and say /z/, and then the /f/ (be careful to produce just the consonant and not accidentally add a vowel to the sound). You should feel the vibration of the voicing (the vibration of the vocal folds) against your fingers during /z/, but not /f/.

Nasals: the air passes out of the vocal tract through the nose. The fact that your nose is involved in creating these sounds is easily demonstrated simply by trying to create /m/ while holding your nose shut with your fingers. You can't do it! If both your mouth and nose are shut, no sound can escape the vocal tract.

Approximants: the tongue or lips restrict or redirect the air as it passes through the vocal tract. Note however, that the air is not so restricted that it causes enough friction to create a fricative.

Blocked Consonants

Stops and Affricates are blocked consonants; they are created when the lips or tongue briefly block and then release the air as it passes through the vocal tract. The difference between a stop and an affricate is that the air built up during a stop is released quickly, while the slower release of affricates causes friction to occurs during the release.

To feel a blocked consonant, place a few fingers in front of your lips and say /t/. Feel how you use the tip of the tongue block the air, then feel the puff of air that hits your fingers as the air that was built up behind the tip of your tongue is released.

Unlike continuous consonants, blocked consonants cannot be produced for an extended period of time.