Sound waves are mechanical longitudinal waves that travel as compressions and rarefactions through a material medium like air, water, or solids.

Quick Scoop: Core Answer

  • Sound waves are longitudinal waves : particle vibrations are parallel to the direction the wave travels.
  • They are mechanical waves : they must have a medium (no sound in a vacuum).
  • They are also pressure waves : made of alternating high-pressure (compressions) and low-pressure (rarefactions) regions.

Mini breakdown

  • In air, sound moves as a series of squeezes and stretches of the air particles, not as an up‑and‑down “wiggle” like light on a graph.
  • Because it needs a medium, sound travels fastest in solids, slower in liquids, and slowest in gases.

So, if you’re answering an exam or quiz for “what type of waves are sound waves?”, the safest full phrasing is:
“Sound waves are mechanical longitudinal (pressure) waves.”

TL;DR: Sound waves are mechanical, longitudinal pressure waves that need a medium to travel.

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