My dream job:

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Across
  1. 4. without echo
  2. 5. echoes are brighter
  3. 6. the act of spreading outward from a central source
  4. 8. an unborn vertebrate in the later stages of development
  5. 9. high frequency sound waves
Down
  1. 1. a bodily organ that is essential for life
  2. 2. fluid collection within the body
  3. 3. similar echo patterns
  4. 7. an electrical device that converts one form of energy into another