Why does “Hoo” produce cold air but “Haa” produces hot air ?

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Tried to figure it out in public and ended up looking like an absolute fool so imma need someone to explain this to me

In: Biology

14 Answers

Anonymous 0 Comments

I disagree with the answers referring to drop in pressure (adiabatic effect), since the pressure difference just isn’t sufficient.

Instead, the answers around speed are more accurate. The body is pretty warm, and the more contact that the air gets with us, the warmer it gets. Even then, rapid air over the surfaces (like our mouths and throats) tends to cool them, so the slower the air is, the more chance the body can keep those surfaces warm with circulating blood.

Also, while “hoo” moves air faster, “haa” has greater turbidity around the vocal chords, which means that the air gets more stirred up and more of it gets in contact with the warm surfaces.

Anonymous 0 Comments

When air moves fast out of the mouth, it sucks in ambient air, which is colder. To test this, blow (“hoo”) on the palm of your hand through a “tube” made of the other palm (make sure it’s tight), or a toilet paper tube.

It has nothing to do with “compression” or Bernoulli principle.

Anonymous 0 Comments

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Anonymous 0 Comments

When you do a “hoo”, the air is coming out from a very small opening which gives it a higher chance to mix with the air around it and cool down.

When you do a “haa”, the air is coming out at a larger volume and needs more time to cool down.

**Edit**
Put your finger right in front your mouth when doing a “hoo” and you will sense that it’s actually just as hot as a “haa”, but cools much faster a few cms away.

Anonymous 0 Comments

There’s two things to note here:

1.

The human body doesn’t feel absolute temperature, what you feel is how much heat is entering (hot) or leaving (cold) your body (That’s why metals always feel a lot hotter or colder than their surrounding, high heat conductivity).

So in the case of your breath, the air comes out faster on the “Hoo” sound. A faster flow of air will carry more heat away from your hand via convection. As someone else pointed out, it is the same reason a fan cools you down even though the air doesn’t get any colder.

2.

The reason the “Hoo” sound produces a faster airflow than the “Haa” sound for the same effort has to do with the opening size in your throat. If your lungs are pushing the same amount of air in both instances, the air will have to come out faster if the opening is smaller.

Think of a garden hose when partially block the opening with your thumb, the water comes out faster!

Anonymous 0 Comments

What you go “hoo” the air your pushing out of your lungs increases in pressure as it moves through the smaller opening in your lips and then quickly decreases in pressure after it’s left. This decrease in pressure reduces its temperature because the air particles are moving further away from each other, dissipating their energy into kinetic rather than thermal.

When you go “Haa” there is less of a pressure difference between your lip opening and the outside air than when you go “hoo” so the pressure change is lower so more thermal energy is kept in the air. Therefore, when you go “Haa” the temperature of the air is closer to the temperature in your lungs.

Its the same reason that you can feel your deoderant can getting cold when you hold the nozzle down for a while. The pressure in the can is decreasing as you let the gas out.

Edit: This affect is known as Gay-Lussac’s Law (aka The pressure temperature law)

Anonymous 0 Comments

How many of you, (like myself) tested the temps for yourself after reading the headline?

Anonymous 0 Comments

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