Picture of Sound, Sound, and more Sound
Range of human hearing, Interference (three ways), Relationship of frequency and size. Lots of different investigations with sound are possible. Here are a few that I do as labs or demonstrations with my high school physics classes.
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Step 1: Stuff You Need

Not much is needed for this.

1. Computer (with Audacity and Visual Analyser)
2. Microphone
3. Speakers
5. Water bottle (and water)

Step 2: Range of Human Hearing

Picture of Range of Human Hearing
Build sound 2.jpg
More Sound 5.bmp
You can use Audacity or a free oscilloscope program, Visual Analyser for this. Both will work as function generators. In Audacity just go to the "Generate" menu and select "Tone". Fill in the frequency you want.

In Visual Analyser you simply click the "Wave" button above the scope window. Set the desired frequency, click apply, then click "ON". Notice the right and left channels are controlled independently unless you click the "Interlock" check box. You can also generate a sweep that will move through a whole range of frequencies. You can change the options for this in the "Sweep" tab.

Then go back to the main window, turn the scope on, and change the input in Visual Analyser from "Microphone" to your output (note, on my computer it is "Stereo Mix", but this depends on your computer). Then you can watch the Sweep in the FFT window, while listening.

The normal range of human hearing is 20 Hz to 20,000 Hz. Your sound card may not really be able to reach these limits however. As you vary the frequency you will find that the sounds in the middle seem louder. We tend to hear better in the middle of our range and not as well at the extremes. How high up can you hear? If you can't hear it (and it's still less than 20,00 Hz) ask a teenager before you blame your sound card.

When you get to the really high frequencies you'll find teenagers tend to wince while adults will hardly hear anything. Just crank the frequency up to around 17,000 or 18,000 Hz and you'll have the teen repeller. As we age our hearing deteriorates. We loose the extremes of our range first.
Great post! I have changed the setting for my computer speakers to sound like an auditurm but forget how ot change it back got any suggestions?
8bit5 years ago
Is there any way to do waveshaping in audacity? Maybe a plugin or anything? Goldwave had a nice graphical one. . .
jarvis0067 years ago
I've tried the 18,000 Hz with the family and only my little brother could hear it. then my sister brought her baby in the room while she was sleeping, and I turned it on to see if there would be any effect. she woke up very alarmed and in a state of panic I haven't seen before.
if you have a dog try it with it. i tried if i could hear it but i cant he he he
Very Good instructable! I learned a lot. I am making a cell phone ringer for teens.
if you can just barely hear it thnk of how bad it is for the dog! yeah, might wanna turn it down so you cant hear it and see if te dog still goes away... i reckon it'd work
JakeTobak8 years ago
17,000 Hz seems to be enough to get my annoying dog to go away. Lucky for me, I can just barely hear it.