• Introduction
• Lesson
• Try It!
• Review & Tasks

Explore 1

Visit PhET Wave on a String and learn more about amplitude, frequency and wavelength. Click Run Now! to start the simulation.

Notice how the motion of the string increases as you increase the amplitude of the vibrations.

• What happens to the speed of the individual particles of the string as you increase the amplitude and frequency of the vibrations? Answerthe particles move much faster
• How is this related to the sounds you would hear at a rock concert? Answersounds get louder and higher pitched as the amplitude and frequency increase

Explore 2

In PhET Sound, you can change the frequency and the amplitude of the single sound source.  Observe what happens to the tone of the sound as you change the frequency.  The pitch of the sound changes as the frequency changes.  If the frequency is high, the pitch is high and if the frequency is low, the pitch is low.

Now select two sources of interference and observe what happens to sound coming from two different speakers.  As you move the listener position, you will notice the sound changing because the sound waves from the speakers overlap and cause areas of high intensity and low intensity. This called interference.    

Because sound waves are mechanical, they affect the particles of air as they pass.  The particles get pushed and pulled in different directions by different sounds coming from different directions.  Sometimes the waves add together and increase the amount of motion of the particles.  This is called constructive interference. 

Other times, the waves subtract from one another and the particle movement is less.  This called destructive interference.  The location of the speakers and the different sounds at a rock concert all interfere either constructively or destructively and add to the overall effect of the music.