Tree Growler

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I wanted a small, portable, battery operated sound effect generator that I could attach to a tree...and that would pump out a bunch of scary sounds. The idea here is that with the sounds coming from the dark tree branches, you just never know what's up there! I have a tree near the street in my front yard that is a perfect place this. Yes, you could stick a Boom Box up in the tree and get the same thing, but geesh...first time it rains (goodbye to your electronics). My setup should survive a rainstorm.

To meet these requirements....I decided I wanted to use the cheapest portable WalMart CD player ($10 these days) with a CD that I made myself. You can find these sound effects all over the Web, but here's the best links I have found:

Sound Effects 1
Sound Effects 2
Sound Effects 3
Sound Effects 4
Sound Effects 5
Sound Effects 6
Sound Effects 7
Sound Effects 8

The CD player runs on 2 AA batteries which will run for many hours. I chose to make a CD with about 2 to 4 seconds of silence between each effect (ghost wail, etc) for maximum startle effect. I found a 2 second "silence" MP3 on the Web for spacers. Note: you can't record any 1 second WAVs, MP3s to a CD. Must have at least 2 seconds. Halloween Sounds Web sites do have less than 2 second audio clips and they don't record!.

I also found that my CD burner software rejected 8 bit files. Requires 16 bit files. Well, OK....these aren't high fidelity. If you are on a PC, you can just use the sound recorder that comes from Windows to bump them up to 16 bit. Then, do your CD burns. I also did some of my own voice recordings (best voice acting I could...with a gruff "Happy Halloween", etc.) Then, just put the player in repeat mode and let it run throughout the time that the TOTs show up.

I found a cheap 4 inch speaker ($5) at a surplus store and mounted it inside a 6 inch plastic flower pot, with the drainage holes down. Then, smeared JB Weld around the rim of the flower pot and attached a plastic storage container lid that just fit. Ran the speaker wire through a hole drilled in the side and smeared with JB Weld. Then, a small block of cedar epoxied to the top of the lid. Viola! A cheap water resistant outdoor speaker...for about $5! I found that any smaller speaker just didn't give the low bass tones I wanted for the effects. You could buy a outdoor speaker if you want, but these are not for $5! Your choice. My speaker was painted black to blend into the tree at night, and is very lightweight.

You can try to drive your speaker (I chose to use just one) with the output of the CD player, but you won't get much volume. The CD player is only meant to drive the dinky little headphones. You can snip the headphone cord off about 4 inches above the plug....strip the wires (each wire has an outer wrap of wire...which is ground...and the inner wire is the right or left of the stereo pair. You just solder the two ground wires together, solder the left and right wires together, and now your stereo CD can drive monoaural (one speaker).

I chose to amplify my CD output with a LM 386 amplifier chip. These little chips can crank out the volume. I used a 9V battery for it's power.

Here's the schematic: Tree Growler Schematic

Note: If you get a hum feedback noise on your amplifier, you may need to add a 10 uf capacitor across the 9V battery output. See this article for more info.

I assembled the all the electronics on a perfboard shown here screwed into bottom of a round food storage bowl. Then, just laid the CD player on top of it. Closed the lid (epoxied a cedar board to the lid to allow for attachment to the tree). Put the speaker wire through the side with JB Weld (and a knot for strain relief). Spray painted it black. Now, it's waterproof too. Here's a view of that.

Tree Growler

Can't wait to try this out next Halloween! I expect lots of scare effects with this gizmo!

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