1. Pressure and Sound

2. A. Density
Compares the mass of an object (grams) and how much space it takes up
2. Density = mass / volume
(cubic centimeters or milliliters).

3. The densest water is really cold and really salty
The densest water is really cold and really salty. Watch this video of an underwater brine lake!

4. B. Pressure
1. We are surrounded by molecules that are constantly pushing on us. 2. Earth’s gravity holds the heaviest molecules closest to the center of the planet (solids) and allows the lightest molecules to float further away (air).

5. Depth of Water Column (meters)
Pressure in Atmospheres
Water Pressure psi (lbs. per. Sq. in. 1 2
0.45 3
0.91 4
1.36 5
1.82 6
2.27 7
2.73 8
3.18 9
3.64 10
4.09 11
4.55
3. Under water, you feel the molecules around you in the water AND the molecules above you in the air.

6. C. Sound
1. Travels in waves of pressure (vibrating molecules). a. The denser the water  the faster the sound travels. b. Waves bend (refract) toward areas of minimum resistance.

7. 2. Communicating with Patterns of Sound
SONAR (SOund Navigation And Ranging)
1) Uses reflected sound waves to create a visual picture.
2) Used by bats, dolphins and navies.
b. Morris Code
1) Communication system that uses sound patterns to communicate messages.
2) Effective with minimal technology or resources.
Morris Code translator

8. c. Sound waves get “trapped” in thermoclines and create a sound channel. d. Navies use low frequency sonar in this zone to map the ocean floor and communicate across ocean basins.

9. 3. The SOFAR Channel
a. SOund Fixing And Ranging b. Sound waves trapped in a thermocline. c. Varies with depth and latitude.

10. 4. Whale Songs
a. Complex patterns that communicate massive amounts of information in the form of narrative histories (stories).
Click here to hear the whales sing…

11. b. Whales and LFS
1) Low-frequency SONAR is used by whales and submariners for communication.
2) Massive amounts of sound are pouring into the SOFAR channel and many scientists believe that this is disrupting communication and navigation for whales.