Air Horns & Sonic BOOM!

f18Sound can change according to the speed at which it travels. Another word for sound speed is pitch. When the sound speed slows, the pitch lowers. With clarinet reeds, it’s high. Guitar strings can do both, as they are adjustable. If you look carefully, you can actually see the low pitch strings vibrate back and forth, but the high pitch strings move so quickly it’s hard to see. But you can detect the effects of both with your ears.


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The Best Parent-Annoyer Ever

This is one of my absolute favorites, because it’s so unexpected and unusual… the setup looks quite harmless, but it makes a sound worse than scratching your nails on a chalkboard. If you can’t find the weird ingredient, just use water and you’ll get nearly the same result (it just takes more practice to get it right). Ready?


NOTE: DO NOT place these anywhere near your ear… keep them straight out in front of you.


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Seeing Sound Waves

This section is actually a collection of the experiments that build on each other.  We’ll be playing with sound waves, and the older students will continue on after this experiment to build speakers.


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Humming Balloon

You can easily make a humming (or screaming!) balloon by inserting a small hexnut into a balloon and inflating. You can also try pennies, washers, and anything else you have that is small and semi-round. We have scads of these things at birthday time, hiding small change in some and nuts in the others so the kids pop them to get their treasures. Some kids will figure out a way to test which balloons are which without popping… which is what we’re going to do right now.


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Good Old Telephone

telephoneThis is the experiment that all kids know about… if you haven’t done this one already, put it on your list of fun things to do. (See the tips & tricks at the bottom for further ideas!)


We’re going to break this into two steps – the first part of the experiment will show us why we need the cups and can’t just hook a string up to our ear.  Are you ready?


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Seeing Sound Waves using Light

After you’ve completed this experiment, you can try making your own sound-to-light transformer as shown below. Using the properties of sound waves, we’ll be able to actually see sound waves when we aim a flashlight at a drum head and pick up the waves on a nearby wall.


Here’s what you need:


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Advanced Students: Download the student worksheet here.


Thunder and Lightning

When there’s lightning, thunder is not far behind.  Even if you don’t live in a tropical thunderstorm area, you can still simulate this experiment using the variations below and get the most out of the main ideas about sound waves and light waves.


For starters, let’s assume you’re waiting for a good storm. When one’s brewing, grab a timer and a pencil with paper and wait inside the house near a window.


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Chladni Plates

chladniThis experiment is just for advanced students. Ernst Florens Friedrich Chladni (1756-1827) is considered to be the ‘father of acoustics’. He was fascinated by vibrating things like plates and gases, and his experiments resulted in two new musical instruments to be developed.


When Chladni first did these vibrating plate experiments (as shown in the video below), he used glass plates instead of metal. He was also one of the first to figure out how to calculate the speed of sound through a gas.


And it will completely blow your mind. Chladni patterns are formed with a metal plate covered in regular table salt is vibrated through different frequencies.


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Building Speakers

Alexander Graham Bell developed the telegraph, microphone, and telephone back in the late 1800s. We’ll be talking about electromagnetism in a later unit, but we’re going to cover a few basics here so you can understand how loudspeakers transform an electrical signal into sound.


This experiment is for advanced students.We’ll be making different kinds of speakers using household materials (like plastic cups, foam plates, and business cards!), but before we begin, we need to make sure you really understand a few basic principles. Here’s what you need to know to get started:


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Buzzing Hornets

hornet1Sound is everywhere. It can travel through solids, liquids, and gases, but it does so at different speeds. It can rustle through trees at 770 MPH (miles per hour), echo through the ocean at 3,270 MPH, and resonate through solid rock at 8,600 MPH.


Sound is made by things vibrating back and forth, whether it’s a guitar string, drum head, or clarinet. The back and forth motion of an object (like the drum head) creates a sound wave in the air that looks a lot like a ripple in a pond after you throw a rock in. It radiates outward, vibrating it’s neighboring air molecules until they are moving around, too. This chain reaction keeps happening until it reaches your ears, where your “sound detectors” pick up the vibration and works with your brain to turn it into sound.


You can illustrate this principle using a guitar string – when you pluck the string, your ears pick up a sound. If you have extra rubber bands, wrap them around an open shoebox to make a shoebox guitar. You can also cut a hole in the lid (image left) and use wooden pencils to lift the rubber band off the surface of the shoebox.


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Harmonicas

Your voice is a vibration, and you can feel it when you place a hand on your throat when you speak. As long as there are molecules around, sound will be traveling though them by smacking into each other.


That’s why if you put an alarm clock inside a glass jar and remove the air, there’s no sound from the clock. There’s nothing to transfer the vibrational energy to – nothing to smack into to transfer the sound. It’s like trying to grab hold of fog – there’s nothing to hold on to.


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