1. 16.6 The Speed of Sound Sound travels through gases, liquids, and solids at different speeds. Room temperature: speed of sound in air is 343 m/s (767 mi/h) and greater in liquids and solids. Sound travels more than four times faster in water and more than seventeen times faster in steel than it does in air. Sound travels slowest in gases, faster in liquids, and fastest in solids.

2. Issac Newton was the first to measure sound. http://www.youtube.com/watch?v=PzUU4 G4uW18&feature=relatedhttp://www.youtube.com/watch?v=PzUU4 G4uW18&feature=related

3. Sound in a gas Only when molecules collide that the condensations and rarefactions of a sound wave can move from place to place. Speed of sound in a gas to have the same order of magnitude as the average molecular speed between collisions.

4. Speed in Ideal Gas Translational rms (root mean square) speed given in the following equation 14.6 T = Kelvin M = mass k = Boltzmann’s constant (relation between absolute temp. and the KE contained in each molecule of an ideal gas) Overestimates the speed of sound. It gives the correct dependence on Kelvin temperature and particle mass.

5. Speed of sound in an ideal gas (16.5) y = cp/cv ratio of specific heat capacity at constant pressure cp to the specific heat capacity at constant volume cv. (adiabatic) Ideal monatomic gas: y = 5/3 (atoms are not bonded together) Y = 7/5 for ideal diatomic gases (composed of 2 atoms) Y is here because the condensations and rarefactions of a sound wave are formed by adiabatic compressions (impassable) and expansions of the gas.

6. Example 4: An Ultrasonic Ruler

9. Practice Problem 44

11. Homework Pg. 506 Ques. 29, 30, 31

16. Sonar Sound navigation ranging Used to determine water depth and locating underwater objects, such as reefs, submarines, and schools of fish. Ultrasonic transmitter and receiver mounted on the bottom of a ship. Transmitter emits a short pulse of ultrasonic sound, later the reflected pulse returns and is detected by the receiver. Depth determined the time it took for the sound to return. http://www.youtube.com/watch?v=Xc2EZjG0b8U &feature=related http://www.youtube.com/watch?v=Xc2EZjG0b8U &feature=related

17. Liquids In a liquid, the speed of sound depends on the density p and the adiabatic bulk modulus Bad of the liquid: (16.6)

18. Liquids Adiabatic bulk modulus B ad is used when calculating the speed of sound in liquids. In seawater sound is 1522m/s (4x greater than in air).

19. In Medicine Ultrasonic probe called an A-scan is used to measure the length of the eyeball in front of the lens, thickness of the lens, and the length of the eyeball between the lens and the retina. Needed information is the speed of sound in the material in front of and behind the lens of the eye is 1532m/s and that within the lens is 1641m/s.

20. Solid Bars When sound travels through a long slender solid bar, the speed of the sound depends on the properties of the medium according to

21. 16.7 Sound Intensity Sound waves carry energy that can be used to do work. Sonic boom: can carry enough energy to cause damage to windows and buildings. The amount of energy transported per second by a sound wave is called the power of the wave and is measure in SI units of joules per second (J/s) or watts (W).

22. Sound Intensity I Power spreads out as it leaves the source. It spreads out but has the same power even when spread out over a greater area. Sound Intensity I: sound power P that passes perpendicularly through a surface divided by the area A of that surface:

23. Example 6: Sound Intensities

25. Example 7: Fireworks

27. 16.8 Decibels