This study examined the relationship between lung capacity, speech volume and duration of utterances. 8 adult subjects, 4 males and 4 females (24-36 yrs), participated. By breathing into a digital spirometer, lung capacities such as Vital Capacity (VC) and Inspirational Capacity (IC) were estimated. Respiratory movements were measured using Respiratory Inductance Plethysmography (RIP), and these respiratory movements were calibrated in litres using the spirometer. The proportion of lung capacity used for speech was estimated from the calibrated RIP signals during reading of a nonsense text without punctuation marks. This proportion was defined as the median volume of exhaled air per utterance (SV) (in litres) during text reading, divided by the speaker’s VC (SV/VC). Utterance durations (UD) and Respiratory Rates (RR) were estimated from acoustic recordings of the text readings as well as the RIP signals, displayed in Praat. This allowed investigating the relationships between lung capacity, respiratory rate, utterance durations as well as the proportion of lung capacity used for speech. Put differently, the question was whether people with larger lungs speak in longer utterances and inhale less frequently, as well as whether people with smaller lungs use a relatively larger proportion of their lung capacity for speaking. Additionally, where SV initiated (SVIN) and terminated (SVTER) within VC was calculated based on the RIP signals. There were no significant relationships between VC and UD or RR. In addition, there was no significant relationship between SV/VC and VC. SVIN ranged from 43%-71% and SVTER ranged from 17%-55%. The results indicate no relationship between VC and UD or RR nor that people with a smaller VC use more of it for speech. The range of SV within VC suggest that people maintain a fairly relaxed state with regards to muscle pressure.

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