Nasal occlusive

In phonetics, a nasal, also called a nasal occlusive, nasal stop in contrast with a nasal fricative, or nasal continuant, is an occlusive consonant produced with a lowered velum, allowing air to escape freely through the nose. Examples of nasals in English are [n] and [m], in words such as nose and mouth. Nasal occlusives are nearly universal in human languages. There are also other kinds of nasal consonants in some languages.

Nearly all nasal consonants are nasal occlusives, in which air escapes through the nose but not through the mouth, as it is blocked (occluded) by the lips or tongue. The oral cavity still acts as a resonance chamber for the sound. Rarely, non-occlusive consonants may be nasalized.

Most nasals are voiced, and in fact, the nasal sounds [n] and [m] are among the most common sounds cross-linguistically. Voiceless nasals occur in a few languages such as Burmese, Welsh, Icelandic and Guaraní. (Compare oral stops, which block off the air completely, and fricatives, which obstruct the air with a narrow channel. Both stops and fricatives are more commonly voiceless than voiced, and are known as obstruents.)

In terms of acoustics, nasals are sonorants, which means that they do not significantly restrict the escape of air (as it can freely escape out the nose). However, nasals are also obstruents in their articulation because the flow of air through the mouth is blocked. This duality, a sonorant airflow through the nose along with an obstruction in the mouth, means that nasal occlusives behave both like sonorants and like obstruents. For example, nasals tend to pattern with other sonorants such as [r] and [l], but in many languages, they may develop from or into stops.

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