<< Back to Lessons Index

Science_Lab_Yellow / Lesson 3: What Is Pitch?

What is Pitch
What will we be learning today?


  • In this lesson, we are going to learn all about what is pitch.


What Is Pitch?


  • Some sounds are "higher" than others; some sounds are "lower." High and low are words that describe the pitch of a sound. In the sixth century B.C., the Greek mathematician Pythagoras (pi THAG uhr uhs) observed that a longer string produces a sound with a lower pitch than a shorter string.


Changes in Pitch


  • What can you do to a rubber band to make different sounds? If you pluck a rubber band to make sounds, you can change the pitch by shortening the rubber band. You make it shorter by pressing a thumb over part of it so less of it vibrates. A shorter string vibrates faster and produces a higher pitch.



  • A second way you can change the pitch is to stretch the rubber band tighter. This causes the rubber band to vibrate faster and, therefore, to produce a higher-pitched sound. The pitch of a vibrating string is also related to its thickness. Compare the strings of this guitar.


  • Did you know that the length and thickness of your vocal cords, and how you tighten or relax them, affects the pitch of your voice?

  • Singers can sing a range from high to lower notes by tightening and relaxing their vocal cords. Men usually have longer and thicker vocal cords than women, so men's voices tend to be lower pitched than women's voices.


Sound Waves


  • You can't see sound waves, but scientists study them with an oscilloscope. This device makes a "picture" of sound waves. An oscilloscope allows you to compare the waves of sounds that have different pitches.



Frequency


  • The higher the pitch, the more "squeezed together" the waves are. Higher-pitched waves have a greater frequency. Frequency is the number of times an object vibrates per second.


  • Frequency describes vibrations and sound waves. Pitch describes how your brain interprets a sound. A flute has a high pitch. A bass guitar has a low pitch. Frequency and pitch are related: the higher the frequency, the higher the pitch; the lower the frequency, the lower the pitch.


    • Frequency is measured in units called hertz. A frequency of one vibration per second is one hertz (Hz). Hertz comes from the name of Heinrich Hertz (1857-1894), a German physicist who studied sound and radio waves.

    • Humans hear from about 20 Hz to about 20,000 Hz. Sounds with a frequency higher than 20,000 Hz are ultrasonic -too high to be heard by humans, but not by some animals.



    Let's Review What We Learned Today!


    • Now complete your worksheet!