Researchers describe an acoustic meta-surface that uses pingpong balls, with small holes punctured in each, as Helmholtz resonators to create inexpensive but effective low-frequency sound insulation.
How one man used the guts of a 1960s telephone to invent a ball that beeps and gave the visually impaired a way to play America's pastime. Even at eight years old, the boy had been playing soccer long ...
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