waves

3. the frequency of sound is lower than the audible frequency.
7. the direction of the wave is parallel to the direction of the movement of particles.
9. the quality of sound.
11. the distance between successive crests or troughs.
12. Time taken for one complete wave to pass a point.
15. Phenomenon when waves strike to a surface and bounce off it.
17. a regular variation in position about a mean
20. the frequency of sound is greater than the audible frequency.

1. characteristic of sound relates to amplitude of sound wave.
2. molecules of air pushed closer together.
4. it is a decompression of the air.
5. matter needed to transfer sound.
6. Waves bend round the sides of an obstacle or spread out as they pass through a gap.
8. the direction of the wave is perpendicular to the direction of the movement of the particles.
10. A reflected sound wave cannot be heard as a separate sound from the original sound.
13. characteristic of sound relates to frequency of sound wave.
14. A reflected sound wave heard as a separate sound from the original sound.
16. the maximum displacement of particles from the rest position
18. Number of complete waves generated per second.
19. abbreviation of Sound Navigation & Ranging