Year 7 Energy, Sound

You experience it constantly, however have you every stopped to wonder what sound actually is? Perhaps you can even hear a voice inside your head reading this out right now… it’s ok you’re not crazy, just a human. It was covered in our Introduction into energy, that sound energy is actually kinetic energy. Copy the below statement into your book:

“Sound is a form of energy. It is caused by vibrations and must travel through a medium”

Note: A “medium” is any substance that contains matter. e.g. air, water, metal, wood etc.

In space, no one can hear you SCRE….

You’ve probably heard this before, and it relates directly to the comment listed above about sound needing a medium to work. In space there is very little to no matter around for your voice box to vibrate and once you release your last gasp of air there is nothing left carry your sound energy.

The above video uses a large vacuum chamber to suck out all the air and see if it’s possible to still hear a sound. There is an in class demo that you’ll be able to see it for yourself although the effect isn’t as good because sound can still travel though the base of a vacuum chamber when setup incorrectly.

How to tune your voice with a fork

In we’ll get a chance to learn (play) with tuning forks. To make a sound with the tuning forks, hit them with force towards the middle on one side and the sound should resonate if you hold them gently at the base.

Pay attention to the follow features of the tuning forks:

  • Numbers stamped on the side. Do they increase or decrease with the size of the fork?
  • How does a low number effect the sound? High or Low pitch?
  • Try holding the base on a desk. Does the volume increase or decrease?
  • Try placing the tips into a shallow dish of water. What happens?
  • Try feeling the movement of the forks on the outer edge of your ear.
Want to learn more about how they work?

Ye olde phones

Back in my day… I had the same technology that most of you have now, just slower and every year a phone got released there were actually new features added to them. SMS cost 25c each to send, so you really had to think if it was worth messaging someone or ensuring that you didn’t go over the 160 character word limit!

Image result for 2009 mobile phones
Phones from 2009

Further back “speaking tubes” were used by navies and in some old homes as a form of communication. You may have seen them at play grounds.

Image result for speaking tubes
Pre-electronic communication
Image result for speaking tubes playground
Playground speaking tubes

Try to recreate this using pipe or paper cups and string. Observe the vibration of the sound energy traveling down the tube or string.

Measuring the speed of sound

There is a speed limit to all the sound that we hear and it varies depending on the object that it’s traveling through. You may have experienced this before in the form of an echo. It can be measured rather easily and all you need is a stop watch and some clapping sticks.

Want to measure or make sound with your phone?

There are many different apps available on the Play or App store which allow you to play with or manipulate in class. A good app used by myself is “Physics Toolbox Sensor Suite”
Play Store link for “Physics Toolbox Sensor Suite”
App Store link for “Physics Toolbox Sensor Suite”

Watch some YouTube videos to learn how to work it or ask your teacher.

Year 7 Energy Topic
Year 7 Energy Topic Vocabulary