Deep-Six Underwater Systems, Inc.
"Add Depth to Your Life"
Contents

Table of Contents

Introduction
1 Pressure and Gases
2 The Face Mask
3 The Snorkel
4 The Fins
5 Weight Systems
6 The Knife
7 The Wetsuit
8 Pressure and Water
9 The Ear and Pressure
10 The Sinus and Pressure
11 The Stomach/Intestine and Pressure
12 The Lung and Pressure
13 Barotrauma caused by External Air Spaces
14 The Buoyancy Compesation Device (BCD)
15 The Scuba Cylinder
16 The Scuba Cylinder Valve
17 The Regulator
18 Density and the Diver
19 The 4 Gas Laws
20 Hand Signals
21 Carbon Monoxide Poisoning
22 Hyperventilation
23 Nitrogen Narcosis
24 Diver's Flags
25 Sound Underwater
26 Color Underwater
27 Decompression Sickness
28 Breathing Oxygen
29 Deep Diving
30 Thermoclines
31 Thunderstorms
32 Underwater Life
33 Open Water Dives
34 The Final Examination
35 The Environment
36 Advanced Course



25 - Sound Underwater

     If you were to close your eyes and I moved to a different spot in the room and made a noise, you would be able to locate my position without looking. How is that done?

     The part of your ear that sticks out from your head (the Auricle or Pinna) acts as a locater. When a sound is produced  the listener will turn their head until the sound is at its loudest. The loudness is at its peak when the pinnas are both facing the sound, capturing it and reflecting it to the small opening into the ear.

     Sound travels about 750 miles per hour depending on several factors. The human brain is fast enough to be able to detect the difference in arrival times of a sound hitting one ear and then the other. When the arrival time is the same the observer is facing directly toward or away from the source of the sound. This is another way a person can tell where sound is coming from.

When a diver is underwater the pinnas do not function as they do in air. Since they are almost the same density as the water, and may be covered by a hood, it's as if they were surgically removed from the head. And, since the speed of sound in water is about 4 times faster (it is about 3400 miles per hour) the brain is no longer able to tell the direction of sound underwater.

     Sound does travel better underwater. Banging 2 rocks together can be heard for miles underwater. Contrast that to sound in the air! So, you will be able to clearly hear your Divemaster banging their tank to get your attention, but it will not be evident as to where they are located. 




Copyright Information about this text, DIVING WITH DEEP-SIX is as follows: Copyright 1996 - 2007 by George D. Campbell, III; President. All Rights Reserved. This file may be posted on Electronic Bulletin Boards for download, but may not be modified, printed for distribution, or used for any commercial purpose without the author's written permission.
scubish.com is using this material with the permission of Deep Six. The full version is available at: http://www.deep-six.com/page50.htm
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