Why is our voice lower when we wake up than when we go to sleep?
In: Biology
Pitch (frequency) is determined by the thickness and length of the vibrating body, and also, in the case of vocal sound, by the shape of the resonating chamber attached to the source of vibration (in this case, the vocal folds). It is true that your muscles relax during the night as you sleep, and it is also true that the mucus in your throat will thicken overnight (in part because your salivary glands shut down while you’re sleeping). However, the biggest factor in morning voice is probably the thickening of the vocal folds overnight due to fluid retention. When you lie down, fluid collects in some tissues in your body (your spine is another place where this happens, which is why getting out of bed is the worst part of the day if you have a disc injury), and when you move around, it redistributes. Surprisingly enough, if you’re more well-hydrated overall, this happens less. But remember, hydration for vocal tissue is systemic rather than direct (when you drink a glass of water, none of it actually touches your larynx…or if it does, you’ve just inhaled water & that’s not good), so the water has to be absorbed via your digestive tract to reach your vocal folds. This means you have to consistently hydrate over time to keep your folds limber.
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