Oral or nasal?

The next major issue is where the pulmonic egressive airstream used in English goes. For most sounds, air passes from the lungs, up through a long tube composed of the trachea, or windpipe; the larynx; and the pharynx, which opens out into the back of the oral cavity. The air passes the various articulators in the mouth, and exits at the lips . However, for three English sounds, air passes through the nasal cavity instead.

The key to whether air can flow through the nose is the velum, or soft palate, which you can identify by curling the tip of your tongue up and running it back along the roof of your mouth until you feel the hard, bony palate giving way to something squashier. For oral sounds, the velum is raised and pushed against the back wall of the pharynx, cutting off access to the nose. However, for [m], [n] and [ŋ] in ram, ran and rang, the velum is lowered, so that air moving up from the lungs must flow through the nose. If you produce a long [s], you will be able to feel that air is passing only through your mouth; conversely, if you hum a long [m], you will notice that air continues to flow through your nose while your lips are pressed together, with that closure being released only at the end of the [m]. When someone suffering from a cold tells you ‘I’ve got a cold id by dose’ instead of ‘I’ve got a cold in my nose’, she is failing to produce [n] and [m] because soft tissue swelling blocks air access to the nose and perforce makes all sounds temporarily oral.

Nasal sounds, like [m] and [n], are produced with air only passing through the nasal cavity for at least part of their production. On the other hand, nasalized sounds, like the vowel in can, preceding a nasal consonant, as opposed to the vowel in cat, which precedes an oral one, are characterized by airflow through both nose and mouth simultaneously.