Why can’t we see sound waves? – Electromagnetic Zone

Question: Why can’t we see sound waves?
- Keywords:
  human body,
  sight,
  sound wave
Asked by anon-225881 to Sameed, Jose, joannabarstow, Heidi, Freya, Chris on 19 Nov 2019.
- Jose Brandao-Neto answered on 19 Nov 2019:
  
  You can!
  .
  Normally, sound waves (which manifest as pressure changes in the air) won’t cause visual changes in the air, but when a plane is flying at close to the speed of sound in air, the pressure itself is higher than normal and causes water vapour in air to condensate, which is opaque and usually known as clouds!
  .
  That you can see, check it out: https://youtu.be/6B4IVcCuIZE

Question: Why can’t we see sound waves?