Instructables

Roaring Cricket Megaphone Apparatus

Picture of Roaring Cricket Megaphone Apparatus
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I made it at Techshop. http://www.techshop.ws/

It is cricket season and even thought I like the sound of crickets; I do not like crickets in my garage or barn. I wanted a non lethal way of removing the crickets. My idea is to capture a chirping cricket and place it in the cage with some food. Take it out away from the home and point it back towards the home. The cricket sound is amplified by the megaphone. I hope to draw the crickets to the louder sound. Call of the wild.

 
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Step 1: Main components of project

Picture of Main components of project

Main components of project:  Large plastic soda bottle, house hold window screen, metal pencil holder and metal paper clip holder (from local dollar store). Not shown is 3 springs, 3 paper clips.

Step 2: Make the megaphone

Picture of Make the megaphone

Cut the end off of a large plastic soda bottle for the megaphone (as shown). I used a razor knife to start the cut, and then switched to household scissors. I used the old trick of cutting outside the line, then go back and re-cut to the line to get a smoother edge. I was planning on leaving the label on for a cutting guide, but I ripped it off too soon. So I used blue tape as a guide to follow.

Step 3: Spring mounting clips and spring assembly

Picture of Spring mounting clips and spring assembly
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I used a small paper clip and wound it around a small pin punch in the middle.

Then I cut it into two useable pieces:

Upper spring clip to be use as the permanent mounting point for the spring

Lower spring bracket for the movable mounting point

I put a permanent crimp to the Upper spring clip and the Lower spring bracket to each end of the spring (did this for all three springs). I am calling this the spring assembly.

 

 
rimar20007 months ago
Good idea, but you should remove the cylindrical part of the bottle, in order to gain a bit of passive amplification.
Fikjast Scott (author)  rimar20007 months ago
What distance or point do you feel I should cut the bottle (horn) at?
I wrestle over the ideas of the horn design. My thoughts were to create a directional speaker so that the focus of the chirping is directed towards my house, to draw the crickets away. Also not being a cricket or cricket expert; my hopes was that not just the sound but the strength of the sound would be more appealing. My initial testing was done at different distances recorded by a human ear. I also have concerns on the horn design negating the perfect sound values.
I also took in consideration the placement to be on the ground, to encourage positive chirping; even though I feel ground placement will clip the sound waves.
Once I hit publish, I looked at the picture and thought that I need to change the upper cage to a solid component to capture the sound (too much focus on output not input). The open cage idea was to keep the crickets alive. Reconsidering my design, the lower portion being open is all I really needed.
Back to passive amplification. My initial design thoughts were to include different horns which were low in cost and interchangeable. Your input is valuable to me. This is the fun part of my projects.
Thank you for your comment.
In Wikipedia there are some data about horns, ie http://en.wikipedia.org/wiki/Horn_%28acoustic%29.

Here you can see my instructable about a passive megahone.
Fikjast Scott (author)  rimar20007 months ago
After your first comment, I took some time to look at your instructables; you inspire me. Thank you for the additional information and taking the time to provide it.
Dream Dragon7 months ago
An interesting idea, and a nice little apparatus. Well done and Thank you for sharing it.

Since you asked about the best length of the "Tube/pipe/horn" and it sits nicely in one of my fields of interest I did a quick look up to see if I could offer some advice. While I know about lengths of resonators etc. I can't find much about cricket song, though the number of "chirps" do seem to be dependant on the ambient temperature. The only figure I could find was 5000Hz which is towards the upper end of average human hearing.

There are two ways in which your device can serve to amplify the sound.

Firstly, the cone like megaphone, helps to move more air for each sound wave, (called acoustic coupling, or Passive Amplification) instead of allowing it to dissipate in all directions. This will give you a directional element, and for maximum effect it should be half a wavelength in diameter.

Secondly the bottle acts as a resonator rather like an organ pipe (open at both ends), and the ideal length will be a singe whole wavelength. However because of the cone like entry it may behave like a partially closed cone or a partially closed pipe also, so the ideal numbers will only give you an approximation of the real effect.

If the frequency of a cricket chirp is 5000hz then the "ideal" resonator will be surprisingly small, about 3 cm. However because this "ideal" is so small and the frequency is only a guess, not to mention the effects on air temperature on the cricket as well as the sound waves, you may find it more useful to consider MULTIPLES of this number.

Experimentation is the answer. Look at different bottles with different neck profiles and lengths, certainly enclosing the cage will help focus the cricket's sound output, but if he is fully enclosed is he less likely to sing?

You may find these links helpful

http://www.instructables.com/id/Phono-Horn-Free-Sound-Dock-for-your-Smart-Phone-t/

http://hyperphysics.phy-astr.gsu.edu/hbase/waves/opecol.html

I hope that information proves useful to you.
Fikjast Scott (author)  Dream Dragon7 months ago
Wow great feedback, thank you for the information and taking the time. I am new to instructables and it is great. Thank you again this information is invaluable to me.
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