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Quoth Wolfram Alpha:

5000 Pascals

≈ 0.51 × lung air pressure that a typical adult human can exert (≈ 9800 Pa)

≈ 50 × sound pressure at the threshold of human pain (≈ 100 Pa)

And yet the news is not filled with stories of severe pain and ruptured eardrums from people puffing in each others' ears. With a 2 order-of-magnitude difference, it seems like even gentle breaths, waving hands to cool off, etc. should be sufficient to cause pain. What gives?

The interpretation of "lung air pressure" here is a little ambiguous, but if we assume that this means "the pressure difference an adult can produce by blowing on a membrane surrounded by air at 1 atmosphere" then the situation seems reasonably analogous to the tympanic membrane.

One obvious difference is that sound is a wave while blowing is a continuous stream. We can avoid this issue by changing them both to a single impulse, like a gunshot and a single puff of breath. This doesn't seem to make the problem go away. Wikipedia claims that 20 Pa is sufficient for "risk of instantaneous noise-induced hearing loss", and you can obviously exhale much harder than this even in a short breath.

I'm guessing the problem is in some misunderstanding of how I'm interpreting the physical quantities, but I'm not sure what that could be.

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When you say "blowing in someone's ear" do you mean putting your face near their ear and breathing out? As in something potentially romantic? Or do you mean planting your lips on their ear to make a vapor lock and trying to inflate them like bubble gum?

The latter would very probably produce hearing damage. And be very painful at the same time. I would urge you not to try it.

But you'd have to work at it to get the pressure seal. Ears are usually not easy to make such a seal on because they are crinkly and odd shapes.

Without the pressure seal you are basically producing a strong wind. Home work: What is the maximum speed somebody can breathe out, and what over pressure can you expect from such?

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  • $\begingroup$ OK, then why wouldn't a strong wind cause pain? A 50 mph wind perpendicular to a surface looks like it would generate a pressure of about 300 Pa according to the wind load formula. $\endgroup$ Jul 3 '18 at 19:46
  • $\begingroup$ @AaronRotenberg Have you ever stood in a 50 mph wind with your ear turned to the wind? I said HAVE YOU EVER STOOD IN A 50 MPH WIND WITH YOUR EAR TURNED TO THE WIND? (Heh heh.) Also, does your homework indicate a 50 mph wind can be produced by a human's breath? Mythbusters says a sneeze tops out around 39 mph. If somebody sneezed directly in your ear, do you suppose it would hurt? (In addition to making you say YUCK!) $\endgroup$
    – user93146
    Jul 3 '18 at 20:51
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The ear is sensitive to pressure because it contains a diaphragm that is open (to the external ear); it is not a diaphragm against a constant pressure, though, but against a vented region, served by the eustachean tubes.

Some kinds of congestion can block those tubes, and changes in air pressure become painful, which is why most airlines have decongestants available for passengers.

So, either a sustained overpressure at the ear, or transient overpressure (as from an explosion) can rupture an eardrum. We avoid creating those situations where possible.

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