CH11 how are we here already

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Across
  1. 2. amplitude
  2. 5. compression
  3. 7. crest
  4. 9. resonance
  5. 11. cycle
  6. 13. standing_wave
  7. 15. hertz
  8. 16. pendulum
  9. 17. eq_pos
  10. 18. rarefaction
  11. 19. wave
Down
  1. 1. period
  2. 2. antinode
  3. 3. compression_wave
  4. 4. frequency
  5. 6. transverse_wave
  6. 8. trough
  7. 10. shm
  8. 12. interference
  9. 14. node