Bob wrote:

My experience is different. When free diving you can't equalize because
you don't have an air feed at ambient pressure. (Your last breath was at
the surface) Unless I am not understanding the term "free diving" which
I believe means diving without tanks. I that case the air inside your
body gets compressed as you descend and you can't equalize by taking in
more air.

Gary


Hi Gary:
Hope I can add a bit of clairity.......... when decending at 75 fps:

Using sport SCUBA
Using "hard hat" either open simi or closed demand or a free flow pot.
Using nothing but your skin (freediving).

To equalize/clear ears need to have the inside preasure abot the same
as water preasure pushing on ear drum. How to do that? With iincreasig
preasure from decent use muscles to force a presure increase. As decent
continues so does presure. And will need to eqalize ears to new and
increasing water preasure. ANalogy wold be to squeeze a balloon with
hands.
Bob

Bob,
I understand all that. I have had a diving licence for 26 years. What
I am saying is you can't equalize when freediving . You can't increase
the volume of air inside your ears to the ambient pressure level when
you took your last breath at the surface (well maybe a tiny bit).

Chris wrote:
When free diving you can't equalize because
you don't have an air feed at ambient pressure.


Of course you do. Every bit of air inside you
(except for that in the unequalized middle ear)
is at ambient pressure.

Chris

You are right but it is decreasing in volume as your body is compressed.
Equalizing is normally understood to be taking new air in at ambient
pressure to equalize in your ears and lungs etc. That is why you
shouldn't hold your breath ascending after breathing pressurized air.
You'll embolize.

Dave wrote:
On Fri, 24 Feb 2006 01:39:46 GMT, Gary said:


My experience is different. When free diving you can't equalize because
you don't have an air feed at ambient pressure. (Your last breath was at
the surface) Unless I am not understanding the term "free diving" which
I believe means diving without tanks. I that case the air inside your
body gets compressed as you descend and you can't equalize by taking in
more air.


You are misunderstanding. An ear squeeze is caused, not by the difference in
pressure between surface pressure and inner ear pressure, but by low
pressure in the inner ear (which may or may not equal what the pressure was
at the surface) compared to the pressure being exerted by the water pressing
on ear drum from the outside. Since your Eustachian tubes where they join
the throat are flat like the opening of a balloon, the increased air
pressure in your throat doesn't get passed through to the inner ear,
creating a relative vacuum, so the ear drum gets "sucked in". Equalizing
consists, not of adding air from the surface, but of opening the path from
your inner ear to your throat (where the air is, as you say, compressed), so
the higher pressure air there can get into the inner ear and eliminate the
relative vacuum.
I understand clearly. What I am saying is that you can't equalize your
internal air pressure without breathing air a ambient pressure except at
very shallow depths. You need to take in air at the ambient pressure to
equalize properly.

Dave wrote:
On Fri, 24 Feb 2006 01:51:49 GMT, Gary said:


Yes. Going from 1 atmosphere to 2 is doubling the pressure. Going from 2 to
3 is increasing the pressure by just half.

1 atmosphere = 14.7 psi
2 atmospheres = 29.4 psi
3 atmospheres = 44.1 psi

The pressure increase is exactly the same for every atmosphere of depth.


Proving my point. 29.4 psi=200% of 14.7 psi. 44.2 psi=150% of 29.4 psi. When
we're talking the effect of pressure increases in the ear drum, it's the
percentage increase that's significant, not the absolute increase. Going
from the surface to 10' you'll notice a big increase. Going from 150' to
160' you probably wouldn't even detect the difference.
Point taken. The perception of changes in pressure is less at great
depths but the pressure change is the same.

"Gary" wrote in message
news:EKwLf.66510$H%4.31397@pd7tw2no...
Dave wrote:
On Fri, 24 Feb 2006 01:39:46 GMT, Gary
said:


My experience is different. When free diving you can't
equalize because you don't have an air feed at ambient
pressure. (Your last breath was at the surface) Unless I am
not understanding the term "free diving" which I believe means
diving without tanks. I that case the air inside your body
gets compressed as you descend and you can't equalize by taking
in more air.


You are misunderstanding. An ear squeeze is caused, not by the
difference in
pressure between surface pressure and inner ear pressure, but
by low
pressure in the inner ear (which may or may not equal what the
pressure was
at the surface) compared to the pressure being exerted by the
water pressing
on ear drum from the outside. Since your Eustachian tubes where
they join
the throat are flat like the opening of a balloon, the
increased air
pressure in your throat doesn't get passed through to the inner
ear,
creating a relative vacuum, so the ear drum gets "sucked in".
Equalizing
consists, not of adding air from the surface, but of opening
the path from
your inner ear to your throat (where the air is, as you say,
compressed), so
the higher pressure air there can get into the inner ear and
eliminate the
relative vacuum.
I understand clearly. What I am saying is that you can't
equalize your internal air pressure without breathing air a
ambient pressure except at very shallow depths. You need to
take in air at the ambient pressure to equalize properly.

You've forgotten that your whole body is compressed at depth, such
that lung pressure is the same as the ambient pressure (give or
take an inch). Thus you can always equalise from lung/throat/
eustachian air. Otherwise all free divers going below 10 metres of
so would be deaf!

JimB

The air in your middle ear is also at ambient pressure. It is
uncomfortable because to get to ambient pressure your eardrum has to
squeeze in. It is still at ambiet pressure. The discomfort is relieved
when you put more volume of air into the inner ear to remove the
stetching of the eardrum.

Wrong: If there is discomfort due to a squeezed eardrum, then the
pressure in the middle ear is _slightly_ above or below ambient.
The discomfort/pain you feel is measuring that pressure gradient.

You are right but it is decreasing in volume as your body is compressed.
Air is compressed, never your body. That's how you survive skin diving.

Equalizing is normally understood to be taking new air in at ambient
pressure to equalize in your ears and lungs etc.
No. Equalizing is shifting a fraction of a ml of air into our out of
your middle ear, all within you, no brearthing (in or out) required.

That is why you
shouldn't hold your breath ascending after breathing pressurized air.
Completely different story.

You'll embolize.
Yet another story.

Equalization is keeping the air in your middle ear at about the
same pressure/volume as the other air inside you and the water
around you.

As you go deeper, you will need to 'pump' minimal amounts of
air into your middle ear by the process you describe as pre-equalizing.

Keep doing it while going down as soon as your ears tell you to.
Pre-equalizing all at once for a deeper skin dive would hurt quite a
bit.

On the way up, the extra air expands and needs to get out of your
middle ear. It usually goes all by itself, you just feel a slight
pressure
and kear a slight clicking noise.

If you feel pain on the way up, try going back down a bit or to at
least
stay level, and swallow several times, yawn, or wiggle your jaw to help

the air out.

If you still experience problems after a bit of practice, you can try
hot Thai food, decongestants, or an ENT specialist. Don't force it,
a small congestion in the Eustachian tube can easily be stronger
than an eardrum.

Dave wrote:
On Fri, 24 Feb 2006 05:20:26 GMT, Gary said:


You are right but it is decreasing in volume as your body is compressed.
Equalizing is normally understood to be taking new air in at ambient
pressure to equalize in your ears and lungs etc.


Here's where you're getting confused, Gary: it isn't "taking in" air that's
significant. It's opening the passage between areas with two different
pressures so that air can flow from the high pressure area to the low
pressure area. The high pressure area is your throat. The low pressure area
is your ear. If you open the passage between the two, they will reach equal
pressure.
Explain to me how the air in the throat got pressurized.

On Wed, 22 Feb 2006 21:25:35 -0800, Evan Gatehouse wrote:

We go to a place in the Gulf Islands that are teeming with giant red
rock crab. These are some of the biggest rock crab that I have seen.
Kids we take sailing go wading in waist deep water and catch a dozen
in 1/2 an hour. The red rock crab has a very sturdy shell compared to
the Dungeness and isn't really commercially caught, but they are super
tasty.

I agree. They're usually a lot smaller and with harder shells so they're
more work to eat, but I think they actually taste better than Dungeoness.

I found nice big ones in, um, not telling... and teeming is the word!

Matt O.