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Across 5. Waves that move side-to-side/up-and-down 6. When waves bend round obstacles, or spread out as they pass through a gap 8. The material a sound wave has to pass through 10. Waves that move forwards-and-backwards 12. A graph that shows how air pressure 13. The waves are reflected form a surface at the same angle as they strike at 14. The acronym of radio detection and ranging 15. What is heard when sound reflects off a hard surface 17. The time it takes for sound to travel to a hard surface and back to the source (2 Words) 18. What echo-sounders do to the area beneath them 19. The maximum difference a point moves from its rest position when a wave passes 20. Weaker sounds mixed in with the 'fundamental' frequency

Down 1. Musical scales are based on these 2. The 'quality' of the sound 3. An instrument that can display waveforms on a screen 4. The musical term for frequency 7. An object that shows waves in water (2 Words) 9. Sound that is above the range of human hearing 11. Waves slow and change direction 16. The SI unit of frequency