#sound.mechanical_phenomenon  mechanical vibrations transmitted by an elastic medium; "falling trees make a sound in the forest even when no one is there to hear them"
  supertype:  #mechanical_phenomenon  a physical phenomenon associated with the equilibrium or motion of objects
  subtype:  #ultrasound  very high frequency sound; used in ultrasonography
  subtype:  #sound_unit__soundunit  any acoustic unit of measurement
     subtype:  #bel__B  a logarithmic unit of sound intensity equal to 10 decibels
     subtype:  #decibel__dB__db__db  a logarithmic unit of sound intensity; 10 times the logarithm of the ratio of the sound intensity to some reference intensity
     subtype:  #sone  a unit of perceived loudness equal to the loudness of a 1000-hertz tone at 40 dB above threshold
     subtype:  #phon  a unit of subjective loudness

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