3. Sound waves travel faster then the gas molecules drift, or migrate.

7. One wavelength.

8. Same speed in all directions (including up, down and everything in between).

11. The resonance frequencies will be disproportionately loud. That is certain notes will have increased volume.

12. Yes. The Doppler effect is caused by a moving sound source, receiver (listener), or both.

14. As the signal bounces off a moving vehicle, the frequency is changed. The change is proportional to the speed of the moving object (the car).

16. Narrows as the speed increases.

20. 2 Hz, 0.5 seconds, 10 cm.

31. No change in speed. Wavelength is halved.

32. Warmer air has faster moving molecules, which collide with other molecules. The faster molecules collide with each other the faster sound travels.

40. Correct. Sound travels at approximately 340 m/s = 0.34 km/s which is about 1/3 km/s.

42. The time required for the sound to reach the back of the parade causes a slight delay in when the beat is heard relative to the front.

43. The larger surface area of the table forces more molecules in motion. This would shorten the length of time the sound is heard.

44. The headphones eliminate the jackhammer sound for the operator only, thus allowing them to hear other sounds. Other observers still hear the full sound of the jackhammer.

2. 3 m/s. Wave speed = frequency * wavelength, and wavelength = 1/period.

3. 300,000 km/s = 300,000,000 m/s and 100 MHz = 100,000,000 Hz. Wavelength = (wave speed)/frequency = 3 m.

5. Note travel time of 6 seconds includes down to the floor and back up to the vessel. Depth = 3 s * 1530 m/s = 4590 m.