This project is a fall out from the Blind Basketball project I was involved in recently. I made an instructable :
One part of the project was to get the students from the School for the blind to get involved in developing a reasonable sound or sounds for the activity they were pursuing. We had two groups of students, middle and High school. We needed a simple and safe ball to use while determining what skills they had or could develop. It also allowed me to gather insight and time to figure out how I could make something small enough to fit in a regulation basketball.
The answer was a Foam Soccer Ball and a cheap mp3 player. It was not as firm as a basket ball and easy to make. I new I had a winner when I saw that the middle school students could play with the Foam Soccer Ball by them selves without supervision. Unlike a bell or bead ball it continued to make sounds when still. The enthusiastic interest in discovering and comparing sounds sealed the deal.
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Step 1: Select a Foam Ball
I selected a 7" Foam soccer ball that I found at a local department store for about $8.00. The only real requirement was that it had a solid but soft foam insides. Any foam ball would have done that was large enough to hold the mp3 player. They came in various colors so I made several from different random colors. When different people requested one they each had a reason for preferring a specific color. Good thing they came in different colors. One word of caution. You DO NOT want to use a Polystyrene or Styrofoam craft ball. They won't hold up.
Step 2: Mark, Drill or Cut Hole
One you have selected your foam ball you need to mark and make a hole just a bit smaller than the diameter of the mp3 player. A one inch drill bit worked well. If you don't have wide drill bits you can mark the area to be cut and use a hobby razor knife to carve out the area. The depth needs to be a little bit deeper than the length of the mp3 player. You can pull the plug out with a needle nose pliers and puck any bits out to shape and smooth the bottom. When you insert the mp3 player it should go in about 3/8" just deep enough to clear the surface. The deeper you go the better protected but harder to retrieve. Remember you can always make it wider or deeper but its more difficult to put foam back!
Step 3: The Mp3 Player
I found 2 or 4 gig SD cards for 3 to 4 dollars and this $2.00 mp3 player on ebay.
It has a 3 watt amplifier, a loud and decent sound and all the controls needed. It has an on/off switch, a rolling switch that changes selection and volume, a usb mini jack to recharge the lithium battery and it will play continuously one or more sounds. You might want to order more than you need, you could get a bad one in a batch. The vendors will usually give a refund, if you ask, so It is always better to have a spare than to be short. The only problem I found was that sometime the slots for the SD card didn't line up perfectly. I used a small screw driver to bend the top part up a little to insure that the SD card couldn't slide over the top into the case. With that fixed I was able to teach a blind 11 year old to completely manage the operation of the mp3 player including creating and downloading sounds. Any sound analyzer that can manage mp3 or wave sounds will work. I use "Audacity" a free sound analyzer that has a version for the blind.
Step 4: Put It All Together
Take any sound or sounds that you like and manipulate them to suit your needs, then down load it onto the micro SD card, turn it on and pop it into the foam ball. Push it in far enough to clear the surface and you have a sonic foam ball!
To remove the mp3 player simply place two fingers on opposite sides of the player and press down, grab the mp3 player on each side a pull out (see picture above).
Step 5: Variations and Results
Besides extensive use by blind middle school and High school students testing the balls. I took several balls to a picnic. Adults kicked, threw and rolled the balls in the grass with out damage. The players stayed secure and you could hear the sounds even with the speaker facing down in the grass. We could still hear the sounds when one rolled under a parked car about 30 feet away. The rechargeable battery lasted all afternoon. If you were concerned about how long it would last you could bring an extra mp3 player and just change it out if the battery runs down while you charge up the first one.
I made a two speaker version by adding another speaker on the other side so that at least one speaker would always be exposed. By pushing two wires through the ball and connecting the second speaker in parallel I got an even louder sound. I had a damaged mp3 player so I just used the speaker and case to hold it in place. If you want to experiment with that you could just use a protected speaker in a case.
Total cost was about $13.00. Thanks for reading this instructable.