Saturday, December 9, 2017

The Physics of Equalizing as a Scuba Diver

I have been scuba diving a few times, and one common exercise for divers is called “equalizing”.  Equalizing is the process of relieving the feeling of pressure in your ears as you go deeper and deeper underwater.  Now, after learning about pressures in physics class, I was curious about what is really going on in the process.  As the divers goes deeper, they experience more and more pressure from the water above them.  The pressure change experienced by a scuba diver going descending 50 m can be seen below.

Change in P = Pbottom – Ptop
Change in P = (Po + pgh) – Po = pgh
Change in P = (1000 kg/m3)(9.8 m/s2)(50 m) = 4.9 * 105 Pa 
= 4.8 atm

The middle of a persons ears are closed air spaces that are only connected to the throat by small closed tubes.  As a diver descends, the air pressure in the body is being increased by 4.8 atm every 50 m, however, the pressure in the middle ear remains the same because it is closed off. This pressure difference can cause the feeling of intense pain in one’s ears, unless the process of equalizing is used. The idea is to open these tubes connecting the middle ear to the back of the throat in order for the pressure in the middle ears to be equalized with the higher pressure built up in the rest of the body.  The technique most commonly used to do this in my experience involves simply pinching your nose and closing your mouth while gently trying to push your breath out.  This allows the tubes to open, and a feeling of relief for the diver as their ears are brought to the same equilibrium pressure as the rest of their body.

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