Nasals

The production of nasals

At the systematic level, English has three nasal sounds, which are all voiced (Table 9.1). In conversational speech, we can observe nasals at other places of articulation as well, in ways that are contextually determined. It is also reasonably easy to find stretches of talk which have oro-nasal airflow, i.e. airflow through both the nose and the mouth.

The nasals have different distributions: [m n] occur both syllable initially and syllable finally, but [ŋ] occurs only syllable finally.

Nasal sounds are so called because when they are produced, air flows through the nasal cavity. The nasal cavity is a space above the palate and behind the nostrils. It has a large surface area because it is filled with ‘conchae’, long, curled bone structures that resemble seashells (the name is related to the word ‘conch’). The primary function of the large surface area is to warm and humidify air as it passes from the outside into the body. The complex structures of the nasal cavity mean that they absorb sounds at some frequencies (much as soft furnishings do) so that the acoustic structure of nasals is also complex. The effect of airflow through the nasal cavity in speech is to dampen the sound that comes out: nasal sounds are relatively quiet and low in volume as compared to non-nasal sounds. Compared to oral sounds, they sound ‘dull’. It is harder to distinguish fine details of nasals auditorily than it is for e.g. plosives or fricatives

Nasal consonants require three main articulations in English. First, they require the velum to be lowered. This lowering of the velum is what allows air to flow out of the vocal tract via the nasal cavity. Learning to control the raising and lowering of the velum is not very easy, since most people are not aware of the velum. One way to become more aware is to open the jaw (as if to make an [ɑ] sound), and then breathe in through the nose, but breathe out through the mouth, and then repeat this. At the transition between breathing in through the nose and out through the mouth, you might hear a quiet popping sound as the velum is lowered. This can make you more aware of the velum’s position.

Secondly, nasal consonants require a complete closure to be made somewhere in the vocal tract: the oral gestures for [m n ŋ] are the same as those for [b d g] except that the velum is raised for [b d g] and lowered for [m n ŋ]. For this reason, nasals are often classed as ‘stops’, alongside plosives: in this case, the term ‘stop’ refers to a sound with a complete constriction in the oral tract, rather than a complete constriction in the vocal tract as a whole.

Thirdly, nasals in English are voiced.

Most of these the properties of nasals can be tested simply. Make a long nasal sound such as [m:::] or [n:::], and then pinch your nose. You should find that the sound cannot be sustained for very much longer once the nose is pinched: this is because the closure in the vocal tract seals off airflow through the mouth, so there is no oral airflow; and by pinching the nose, airflow through the nose is also blocked.

Next, make a [s:::] sound. You may be able to make a nasalized [s] sound,  , by lowering the velum. If you achieve this, the amount of friction will diminish rapidly as you move from [s] to  , and the fricative will sound weak and ‘thin’ compared to [s]. However, you can restore some of the volume to  by pinching the nose again, blocking nasal airflow.

Finally, try a simple experiment with a friend. Make nasals at a few places of articulation, including labial, labiodental, dental, alveolar and postalveolar; but do this out of sight, e.g. with your back turned or with your hands in front of your mouth, so that they cannot see the articulation. Ask them to guess the place of articulation. Most likely, they will not be very successful. The reason is that that nasals are not, by themselves, very distinctive, because the nasal cavity absorbs a lot of acoustic energy. Most information about place of articulation for nasals is located in the transitions into and out of the nasal occlusion which correspond to the closing phase of plosives.