Editing Phonetics (section)

===Pulmonary and subglottal system===
{{see|Breathing}}
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The lungs drive nearly all speech production, and their importance in phonetics is due to their creation of pressure for pulmonic sounds. The most common kinds of sound across languages are pulmonic egress, where air is exhaled from the lungs.{{sfn|Ladefoged|2001|p=1}} The opposite is possible, though no language is known to have pulmonic ingressive sounds as phonemes.{{sfn|Eklund|2008|p=237}} Many languages such as [[Swedish language|Swedish]] use them for [[paralinguistic]] articulations such as affirmations in a number of genetically and geographically diverse languages.{{sfn|Eklund|2008}} Both egressive and ingressive sounds rely on holding the vocal folds in a particular posture and using the lungs to draw air across the vocal folds so that they either vibrate (voiced) or do not vibrate (voiceless).{{sfn|Ladefoged|2001|p=1}} Pulmonic articulations are restricted by the volume of air able to be exhaled in a given respiratory cycle, known as the [[vital capacity]].

The lungs are used to maintain two kinds of pressure simultaneously to produce and modify phonation. To produce phonation at all, the lungs must maintain a pressure of 3–5&nbsp;cm H<sub>2</sub>O higher than the pressure above the glottis. However small and fast adjustments are made to the subglottal pressure to modify speech for suprasegmental features like stress. A number of thoracic muscles are used to make these adjustments. Because the lungs and thorax stretch during inhalation, the elastic forces of the lungs alone can produce pressure differentials sufficient for phonation at lung volumes above 50 percent of vital capacity.{{sfn|Seikel|Drumright|King|2016|p=176}} Above 50 percent of vital capacity, the [[respiratory muscles]] are used to "check" the elastic forces of the thorax to maintain a stable pressure differential. Below that volume, they are used to increase the subglottal pressure by actively exhaling air.

During speech, the respiratory cycle is modified to accommodate both linguistic and biological needs. Exhalation, usually about 60 percent of the respiratory cycle at rest, is increased to about 90 percent of the respiratory cycle. Because metabolic needs are relatively stable, the total volume of air moved in most cases of speech remains about the same as quiet tidal breathing.{{sfn|Seikel|Drumright|King|2016|p=171}} Increases in speech intensity of 18&nbsp;dB (a loud conversation) has relatively little impact on the volume of air moved. Because their respiratory systems are not as developed as adults, children tend to use a larger proportion of their vital capacity compared to adults, with more deep inhales.{{sfn|Seikel|Drumright|King|2016|pp=168–77}}