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Old 7th March 2005, 12:46 AM   #1
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Default School Project ideas anyone?

I'm in the International Baccalaureate program at my high school. We have to start coming up with ideas for our paper that is due next year. We have to do thorough research about our topic (thorough for a high school project) and the topic has to be very specific. I asked if I could build a Gainclone and do distortion test vs. commercial amps, but I was turned down. Some physics topics I read about had to do with the way hot air balloons travel and different balloon shapes. The other was an awful topic that had to do with solar pannels, and how they would work more efficiently, the answer was, move them closer to the sun.

I would like to do a project related to audio or electronics.

I'm supposed to come up with 5 ideas by tomorrow, any ideas?

Thanks,

Josh
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Old 7th March 2005, 03:53 AM   #2
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How about that old subwoofer standby-At Which Frequency Does Sound Become Directional?

Take two speakers capable of going down to 50 Hz-shouldn't be hard. Put them far apart, with a chair between them. Take tone generator-they have online ones, or you can make a CD or cassette tape from an online one-and play a series of tones going up from 50 Hz.

Test a number of people-five, ten or more.

The best way to test them is, blindfold them. Test each one individually in the chair. Move up the scale with the tones, but each tone can be played on only one channel. So play 50 Hz on the left channel, then play 50 Hz on the right. Then 60 Hz one channel, then 60 Hz on the other. Record how often each test subject gets the channel right. then move up to 80 Hz, 100 Hz, 120 Hz, etc.

See which percentage of the test subjects finally get the channel correct.

Hint: Don't be too surprised if you have to go well over 200 Hz before there is any decent percentage of subjects who can say which channel the sound comes from.

There will be no one frequency where suddenly everyone can perceive the channel. Rather, there should be an increasing percentage of subjects getting it right the farther you move up the scale from 50 Hz to 600 Hz or so.

I'll leave it up to you to make charts of increading accuracy, or to choose a percentage, (say, 75%) of subjects getting it right, and seeing which frequency that occurs at.

That will be up to you. What should be proven is the higher the frequency, the greater percentage of subjects will be able to tell which direction, (channel) the sound is coming from.
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Old 7th March 2005, 03:58 AM   #3
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This next test will require a decent subwoofer, and a calibrated SPL meter-you might be able to use Speaker Workshop freeware, or even a Radio Shack SPL meter-there is a web site with a calibration curve.

Again, thake a "jury" of several people, and move down the scale from 100 Hz on down. Keep the SPL constant-say 90 decibels. Keep moving down the scale with each subject and ask at which frequency they can no longer perceive the sound.

It will vary from subject to subject. It will also vary from SPL level to SPL level. You wil find that people can hear lower at 100 dB SPL than 90 dB SPL. And if you can have the hardware, you will find that people can hear lower frequencies at 110 dB SPL than at 100 dB SPL.

Chart the results.
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Old 7th March 2005, 04:11 AM   #4
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The next experiemnt might involve getting some cheap speakers on special from Parts Express, lol.

Tkae a regualr, normal speaker. Move outdoors, place against a wall or garage door if possible. Run a steady tone through it. Stand a foot in front in front of it, and measure with an SPL meter. Then move back to 2 feet in front of it. Not how much the SPL drops. Then double your distance again to 4 feet, and note the SPL drop. Then move back to 8 feet, 16 feet, 32 feet, etc.

Then get some cheap specials from Parts Express, and build a tall thin enclosure with a large number of small speakers in a vertical array. The array shold be 2 feet or more high.

Repeat the experiment. Start off at 1 foot in front, then 2', then 4', then 8', 16', 32', 64' etc.

You should find that the vertical array drops off less the farther you move back than the regular speaker does.

Chart the distance, chart the droppoff, then change the frequency and try again. There should be a difference.
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Old 7th March 2005, 11:56 AM   #5
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I need something more of a paper than an experiment.

BrianGT suggested the Transmission Line Theory, which could be interesting.

I like the idea of line arrays, I could test that theory.

Are there any more ideas. Even though I had to have 5 topics by today, I don't have to choose a single one yet and I'm interested in hearing more ideas.

Thanks,

Josh
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Old 7th March 2005, 12:08 PM   #6
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You could aways have a go at testing cable directionality...
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Old 8th March 2005, 04:54 PM   #7
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Pinky,

You're being rather devilish. Trying to start a fight or something?

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