science

4. a wave that requires a medium to travel
6. what frequency is expressed in
9. a measure of how far the particles in the medium move from their normal rest position
11. particles move back and forth in the same direction that the wave travels
13. happens when a sound wave matches a natural frequency of an object
14. the speed at which a wave travels
17. the time required for one cycle of waves
20. tells how many waves occur in an amount of time

1. sound waves that have frequencies greater than 20,000 hertz
2. unit used to express loudness
3. a disturbance in electric and magnetic fields
5. uses of echoes to find objects
7. a disturbance that transfers energy from one place to another
8. longitudinal wave that is caused by vibrations and travels through a medium
10. particles move perpendicularly to the direction the wave travels
12. distance from any point on a wave to an identical point on the next wave
15. the material through which a wave travels
16. measure of how well a sound can be heard
18. a reflected sound wave
19. how high or low you think a sound is