Sound Waves
Sound is a pressure wave through matter.
About this topic
Sound is a longitudinal pressure wave created by a vibrating source and transmitted by particle collisions through a medium, so it can't travel in a vacuum. Its speed in air is about 343 m/s at 20 °C, faster in liquids (1500 m/s in water) and solids (5000 m/s in steel).
Warmer air carries sound faster, about 0.6 m/s more for each degree Celsius, because particles move quicker and pass on the disturbance sooner. Sound is also faster in stiffer materials. The wave is a series of compressions, where air pressure is slightly higher, and rarefactions, where it is lower, and our ear drums respond to those pressure changes.
Worked example: lightning is seen almost instantly but thunder arrives later. Counting 6 seconds between flash and bang means the storm is about 343 × 6 ≈ 2 km away. A shout across a canyon whose echo returns after 4 s means the far wall is about 686 m away.
Applications include speech, music, sonar, ultrasound scanning and architectural acoustics. In space, explosions are silent because there is no medium. A common misconception is that sound travels faster in denser materials purely because of density; in fact stiffness matters most, which is why it is faster in steel than in air. Another is that the particles travel from the source to the ear; they only vibrate in place.
Key ideas
- Needs a medium
- Speed ≈ 343 m/s in air
- Faster in solids
Quick check
Use cases: where Sound Waves helps
- Homework: review the key idea behind Sound Waves before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Sound Waves without notes.
- Visual learning: play with the interactive lab to see how Sound Waves changes when you adjust its inputs.
- Teaching a friend: explain Sound Waves in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Sound Waves?
Sound is a pressure wave through matter.
What will I learn in Sound Waves?
Needs a medium. Speed ≈ 343 m/s in air. Faster in solids.
Is Sound Waves part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Sound Waves lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Sound Waves?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.