Instructables

Dollar Store Parabolic Mic

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Picture of Dollar Store Parabolic Mic
This is a ridiculously easy way to build a very functional parabolic microphone using mostly items purchased from one of those stores where everything is a dollar. Check out the original design at: .Dollar Store Parabolic Microphone
 
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Step 1: Gathering your materials.

First, gather all the materials you will need. This is very easy. In fact, this whole project is so easy you almost don't even have to have the instructable.

Find a small folding umbrella hat, a regular nine inch paint roller handle, and small microphone. Make sure the umbrella hat is vinyl and not fabric. Fabric is too acoustically transparent and will not reflect the sound properly. Just about any small microphone will do as long as it is reasonably sensitive. Here I am using a stereo "Clip-On" mic from Radio Shack (33-3028).

You will also need a few tools and supplies. This is basic stuff. Get a hammer, side cutter, sharp knife, razor saw, permanent marker, some gaffer's tape, and a few cable ties. The reamer is optional. A file might come in handy. So might a small laser pointer of some sort.

That's it!

A little note for "dollar store purists:"

It is possible to build this whole thing using only components from the dollar store. Many of them sell small earbud headphones that can function like microphones, albeit very poor ones. The also sell little hands-free headsets for cell phones. Those have real microphones in them. They will require a little surgery to work but a dollar store purist won't mind. Using either of these options will give you a true $3 parabolic mic

Step 3: Make a Hole for the Handle

Picture of Make a Hole for the Handle
CutTop_1.jpg
ReamHole_1.jpg
Next, take a look at the very top of the umbrella hat. See that little knob? Slice it off with your razor saw and clean up the hole with a reamer or sharp knife as needed.

Done? Then the parabolic part is almost complete. I told you this was easy.
Thanks for the useful feedback.
I hooked up a headset with boom mic to my Sony ICD-B600 recorder. Tests fine for recording from the mic and for listening back through the headphones. But I can't hear in the headphones until after the event. What I need is to hear live, as it happens, not on playback from recording. Any ideas for that?
jurtle (author)  Infomasters1 year ago
I don't know that particular recorder but I assume it is one of Sony's small voice recorders. Many such recorders do not allow monitoring while recording so as to avoid any possibility of feedback. Unless your recorder has a live playback option, you may be out of luck. You might try splitting the mic output and running one leg into a small headphone amp but that is another piece of gear in the mix. I have a small Olympus voice recorder that does allow real time monitoring. Maybe a different recorder for you?
Falconldo2 years ago
Great idea, and sparked some great NFO in the discussion.

I found many hats on Amazon:

http://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=umberella+hat

if that link doesn't work, here is a tiny URL to the same spot:

http://tinyurl.com/blvfud8

There are many that are Amazon Prime eligible... which means you get it in two days and no charge for shipping. IMHO, Prime is worth the yearly fee for that reason alone (it has changed the way I shop forever), but there are many other benefits. If someone you know (Dad) has prime, they may not know that they can put 3 other members on there account and get most of the perks.

Again, I love it!
jurtle (author)  Falconldo2 years ago
Thanks for the tip about finding hats online. Most of those I have looked at are made of nylon, not vinyl, so they are more acoustically transparent and not as effective as parabolic reflectors. That said, the nylon hats do work but with some slightly diminished performance. I have not done this but I think that a coating of clear varnish or some other kind of sealant might make all the difference.
integrator3 years ago
I wonder if I could figure out a way to make small whisper dishes, like you see at science centers and such? Two of them pointed at each other, you stand in front of them and talk into them, and the reflected sound is heard at the other one 50 or 100 feet away. If it's to small, you may block it though.
I first saw two such dishes at the Exploratorium science museum in San Francisco, CA, in the early eighties. Each dish was about 6 feet in diameter. The effect was astonishing. Twenty-five years later I visited the old Roman city of Jerash in Jordan. The outdoor theater there is still in use today. Find a picture if you can. The horse-shoe shaped wall that encloses the "floor" area in front of the stage is carved all around with mini dishes that are about two feet in diameter and no more than about 6 inches deep, if I recall correctly. They work perfectly to transmit and amplify sound across the floor--at least 50 feet. According to our guide, they were used in Roman times as a novel way of trading gossip during performance events. This model suggest your idea could work. Good luck.
jurtle (author)  integrator3 years ago
All of the whisper dishes I have seen are fairly large, usually four feet or larger in diameter. They are passive devices and fixed in location. They tend to work better if the participants in conversation have their backs to each other. In general, the larger the dish, the larger the gain. Once you start getting into the smaller sizes, you will encounter the problem of less gain compounded by the acoustic "shadows" cast by the heads of the participants. If you built two active devices such as the one in this instructable, you could achieve the same effect, except that the communication would be electronically amplified (as well as reflectively amplified through the parabola). Simply have the two participants point their respective devices toward each other and chatter away. Unlike the ordinary whisper dish sets, these would not be fixed in location. and the participants would be facing each other.

Good luck with your experiments.
clibanarius2 years ago
So if you happened to have access to a shotgun mike, could you improve its performance by fitting it into one of these babies? I don't actually have a shotgun mike yet, so I'm not sure whether or not the two gadgets are compatible.
jurtle (author)  clibanarius2 years ago
No real advantage to be gained by pairing the two. They work in different ways. Shotguns actually work by excluding off axis sounds. They are directional because of that. Parabolics gather sound from a larger area (so to speak) and focus it toward a more or less single point. They are directional but for different reasons. You would be better off deciding which technology you wanted to use then try to optimize that one.
bigskyjack3 years ago
i like ur style! i made my own parabolic mic a while bak from 1 of those clip-lites for keeping chicks warm, just took out the bulb socket & replaced with a cork with a hole (chem lab style), ran a wooden dowel thru for the mic boom. for the tuning of the mic placement, i found i needed a distant, constant, 'white-noise' source, so i stuck a small transistor radio tuned between stations out the other side of the yard - worked perfectly - & ur rite, the human ear is by far the best sensor for that 'sweet spot' for the mic!
jurtle (author)  bigskyjack3 years ago
Thanks. I am glad the project resonated with you. I guess it is clear that I had a ball doing it and even more fun interacting with others who like the project.
I love this Instructable!
So you know those really crinkly emergency blankets that resemble foil? Would lining the inside of the umbrella (using spray adhesive or the like) with that help provide better sound? My reasoning with this thought was that the metal-like surface would reflect sound waves better than just the vinyl.
jurtle (author)  KingOfCatfish3 years ago
Glad you like the Instructable. It was fun to put together. As for lining the umbrella with the rescue blankets, I think you would get only marginal improvement if any at all. Those blankets are usually made of mylar, another plastic-like material. Adding another really thin layer of plastic (and glue) to the umbrella might make the whole thing slightly more rigid, thus making it slightly more reflective. My guess is that one would hardly be able to tell the difference in an A-B test. Don't confuse the shiny, almost mirror-like, look of the mylar with good acoustic reflectivity. It will make a much better reflector of light but not of sound.
Thank you for getting back to me. My eyes have now been opened, ha-ha. So I was looking at some pieces of Lexan that are at my house from another project and was wondering is forming it into a parabola would work. What do you think the outcome would be?
jurtle (author)  KingOfCatfish3 years ago
I assume you are talking about flat pieces of lexan. Yes, you can fabricate a parabolic reflector from that material. It will require some cutting and gluing. Here is a link that will get you started: http://vzone.virgin.net/ljmayes.mal/var/parabola.htm Otherwise, just do a google search for something like "Make a parabolic reflector." Lots of idea out there. Good luck.
scraggy124 years ago
Hey , can I use an old direct tv dish?
jurtle (author)  scraggy124 years ago
Yes, but because the dish is so shallow, the focal point is farther away from the surface. It will work but you won't get as much gain. See an earlier comment/reply on this subject. Good luck
jacko6224 years ago
Could you use a regular umbrella for this? 
jurtle (author)  jacko6224 years ago
There is a major difference in the configuration of the hat and a regular umbrella. In the case of the regular umbrella, there is the center shaft to contend with. Perhaps instead of removing it, one could re engineer it to be the on-axis mic support. That way you have a support for the ribs and a support for the mic. Then it would be a matter of configuring a handle for the device. Here is where your own builder/hacker/engineer self comes into play. Go for it.
dakellymon4 years ago
 Well done. Great idea.

wingo3954 years ago
Oh one more thing - You showed in the photos but perhaps it is worth mentioning - you want the microphone element pointed IN to the center of the umbrella, not outwards.  This is to pick up all of the reflected sound bouncing off the surface of the umbrella and to the focal point.
jurtle (author)  wingo3954 years ago
Good call. I did show the mics facing inward in the photos but nothing is said about it in the text. I will probably amend to make the addition. Thanks for the input.
jurtle (author)  jurtle4 years ago
I have amended the text to point out that the mic should face inward toward the umbrella. Thanks for the input.
pyro ray4 years ago
Ok for those of you interested I found umbrella hats online for like 2.99 ea at a lot of places, from But they are made out of nylon. But you can also take a can of spray paint to the unbrella to close the "pores " of the nylon
jurtle (author)  pyro ray4 years ago
I have not tried that approach but I do think it would work. Anything you can do to reduce the acoustic transparency of the nylon fabric will help. That said, you can still get some detectable isolation of the sound source, even with an untreated nylon umbrella. You might be surprised.
ilpug jurtle4 years ago
 use metallic spraypaint to boost the reflectivity of the umbrella... you could even use aluminum foil to line the umbrella. i used a coat of metallic stove black high-heat paint and used a full can... several coats helped alot. i have used these for getting audio on films, and they work great.
wingo3954 years ago
Very nice project!  If you really want to get accurate (as accurate as possible given the flexible nature of the umbrella hat), you can calculate the focal point.  All you need to know is the diameter of the dish and the depth of it.

A simple google search will turn up oodles of info:
http://www.google.com/search?q=calculate+the+focal+point+of+a+parabola

I once bought a parabolic dish (without the mic) from a college, and I bought a very sensitive electret microphone (electets have batteries in them to amplify the signal).  I don't know if it was omni or unidirectional.  My guess is omni might be better, but would need experimentation.  The funny part?  I have yet to put it all together!!

jurtle (author)  wingo3954 years ago
Glad you liked the project. Yes, one can easily calculate the focal point from diameter and depth in a true parabola. That said, there is no reason to believe the umbrella is actually made to conform to such standards. As I have said in previous posts, the focal point on this device is fuzzy at best. Better to use the methods suggested to get the best result. Much of the physics (and math) that applies to parabolic focus with point sources from infinite distances (therefore parallel rays) just does not apply with variable wavelength sonic sources from variable distances and angles. Too much accuracy is overkill.
herrdoktor4 years ago
 Could you use a large, plastic salad bowl instead of an umbrella?
jurtle (author)  herrdoktor4 years ago
Yes. Almost any roughly parabolic surface will work. You just have to find the focus or sweet spot for the dish you are using. Of course, the more accurately it approximates a parabola, the better off you are.
 Thanks, I'll give that a whirl. Have a dollar store down the street, want to try this out with my kids. We live in the country, so hope to capture a number of sounds. Very cool instructable, thanks for posting.
Hey I'm having some trouble acquiring the vinyl umbrella. Any ideas of where I should look? I tried the dollar store (Dollar General) and few other places and haven't had any success. All i've find is nylon so far.
You could just cover the nylon umbrella with aluminum foil
jurtle (author)  threedagreexo155 years ago
Sorry you are having trouble finding the vinyl ones. Mine came from a chain called Dollar Tree. I think the items are seasonal so you might have better luck in the coming weeks as the weather warms up (at least in the northern hemisphere). As a last resort you could still use a nylon umbrella if you were willing to coat it some way so as to reduce the acoustic transparency. I think a few coats of shellac would work. The umbrellas are cheap enough to experiment with. Maybe something like Mod Podge, available any hobby or craft store, would work. Good luck with the project.
Thanks. I just realized that I've been looking at regular umbrellas instead of hats. Is there a major difference between the two? It looks like the regular umbrellas need the rod in the middle in order to hold the rods that hold the umbrella out, so removing that might be difficult.
jurtle (author)  threedagreexo155 years ago
There is a major difference in the configuration of the hat and a regular umbrella. In the case of the regular umbrella, there is the center shaft to contend with. Perhaps instead of removing it, one could re engineer it to be the on-axis mic support. That way you have a support for the ribs and a support for the mic. Then it would be a matter of configuring a handle for the device. Here is where your own builder/hacker/engineer self comes into play. Go for it.
jurtle (author)  threedagreexo155 years ago
Another thought: You might also try looking in a toy store for kids' umbrellas. I think I have seen transparent vinyl umbrellas in places like Toys R Us or Target. Modification of the umbrella would be very different but perhaps worth the effort.
BIGFATSO5 years ago
(removed by author or community request)
(removed by author or community request)
jurtle (author)  BIGFATSO5 years ago
Begin your research into microphones here:
http://en.wikipedia.org/wiki/Microphone
I am going to stay out of that business with your neighbors. You probably should too.
jurtle (author)  BIGFATSO5 years ago
Glad you like it. This is probably not your best bet for secretive recording. It does stand out. My guess is that it will work through a screen but I have never tried it. Good luck.
hellequin5 years ago
Excellent demonstration... In your sample, I found that as with most parabolic reflectors – professional or otherwise that I have on occasion used, there is quite a bit of base rumble in the 40 > 100 Hz area. But a lot of this can be filtered out using various low-pass filters and EQ. A very commendable effort and a great solution... Bravo!
jurtle (author)  hellequin5 years ago
Thanks. You are right about the low end emphasis. I think a more rigid reflector would probably take care of some of the problem. Some sort of shock mount for the mic would help as well. The challenge would be to make such modifications while staying within the "dollar store" range. Thanks again. Glad you liked the project.
ee0u30eb5 years ago
Two things...

1. http://mscir.tripod.com/parabola/ a great program to calculate the exact focal point so you can put the mic in the right spot.

2. I bought one of those spy listeners sold for kids, opened it up and soldering long leads to its mic. If you use that you have a great instant amplifier and mic for your project. I also suggest removing the button cell (usually 1.5V cell) and solder on an AA battery holder. By using an AA battery you get more current and better amplification.

jurtle (author)  ee0u30eb5 years ago
Excellent feedback on both counts. Thanks. On the matter of the calculator, finding the exact focal point in this kind of device doesn't always produce the best results but it does give the best starting point. I have found that one has to fudge it a bit because the parabolic surface is imperfect. The best sound is most often somewhere off of the parabolic focal point. The ear is the best tool for the final adjustment. Some of those spy listeners for kids are great. Others are pretty crappy. I have a couple "Supersonic Ears" from Wild Planet toys. They work very well but cost about twenty bucks. Nice idea for an instant mic/amp combination though. If one is inclined to the the soldering and modifying anyway, it might less expensive to get a mic capsule, and one of those mini amps ( Model: 277-1008) from Radio Shack. The output quality would certainly be better.
ee0u30eb jurtle5 years ago
We don't have a radio shack in the UK, but I might investigate mini-amps in maplis. Worst case scenario, I will just build my own amp, there are plenty of good circuits out there. There is I believe an instructable about reverse engineering a kids spy listener... so if one had one knocking around they could swap out the transistors to improve its amplification. Great instrctable, thanks
samba005 years ago
I have a bunch of old cordless phones. Would the mic from one of those be suitable?
jurtle (author)  samba005 years ago
My guess is probably not. Cordless phone mics do not have to be very sensitive since one speaks directly into them. You would be better off going to Radio Shack and buying a small mic capsule from the components section and using that. I know those work very well and are very sensitive. They can be wired to plug right into some recorders without the need for an extra battery. Wiring diagrams are on the package.
on that hdtv antenna using a direct tv dish, what is the screen for? it's not hooked up to anything and doesn't serve a purpose so why have it?
jurtle (author)  buttcheeksaflappin5 years ago
I don't know but I think it is unlikely that a manufacturer would assume the expense of adding something that serves no purpose. Even if it is purely cosmetic, it has that purpose. I hope you can find out the answer.
Cool, looks great, those fake heads are creepy..
I second that
3rd
fourth would probably be overkill, but might as well put it out there.
5th would be more ridiculous than this instructable.
6th? Why not. Great instructable btw
7th
OMGoodness they are soooo freaky I hearby 8th that motion!!!!!
9th!!! :D
10th just to keep this rolling. awesome instructable by the way
elevendty billionth. awesome instructable, i am going to the Shack tomorrow!
Elevendty billionth squared
Infinity. Pwned
Infinity squared Double Pwned
Infinity10,000.

WHAT?!
Get some.
infinity to the infiniteith power! thats pretty big
Yes, its pretty big. So big in fact that its actually infinity. Oh, the irony. :O
it's OK guys. Just take deep breaths and think happy thoughts. we get the picture with this whole 'second, third, fourth' thing :P
Holy crap...we have created a monster THE END, SERIOUSLY THE END
No, this only the beginning MAWAHAHAHAHAHAHAHAHAHAHAHAHAHHAHAHAHAHAHAHAHA!!!!!!!!!!!!!!!!!!!!!!!!!!
lets start it over! jk jk lol
Ok, why not? Cool, looks great, those fake heads are creepy..
Me vuelvo mono!!!
infinity to the infinity power to the infinity power to the infinity power.
please. No.
Infinity to the Ninja power
n8man bowmaster6 years ago
Infinity to the infinitieth power infinity times. So its infinity to the infinity to the infinity....... and so on Beat that!!!
you really can't get any higher than infinity. lets really start over now!
You're just mad that I beat you Pwnd
I know you are.
but what am I?
What did Geoffrito just finish saying?
He told us to go to our happy places and this is mine
bowmaster n8man6 years ago
Ninja to the power of Ninja
ninja isn't a number
Infinity is actually theoretical so Googleplex to the googleplex to the googleplex and so on
jurtle (author)  n8man6 years ago
Okay, Children. It is time to go out and play somewhere else. My inbox keeps getting these "You have 1 new comment" messages, almost all of which have absolutely nothing to do with the project. Please. There is no way to "win" this ridiculous game of ordinal one-upchildship except to get the last word before the moderator simply deletes the whole batch. I am happy to respond to all relevant comments about the project itself but this thread has gone far enough.
n8man jurtle6 years ago
You could try turning off the alerts or just set them for every hour. Sorry for the earlier comments.
i'm done. cause u can't go any higher.
hello?
bowmaster jillg5 years ago
Pi squared
OKAY STOP THIS IS UNPRODUCTIVE AND MAKING THIS PAGE DIFFICULT TO VIEW. PLEASE.
We've Created a monster!!!!!!!!!!!!
Lets name it Fred.
well, it was asleep, but now you woke it.
I RULE THE WORLD MWHAHAHAHAHAHAHAHAHAHAHAHAHAH!!!!!!!!!!!!!!!
Guys. Seriously. i think its time we all quiet down and go to out respective happy places.
infinity to the infiniteith power squared!!
Ghost Wolf5 years ago
do you like or not like? >:D
Ghost Wolf5 years ago
OMG this works great! I love it I used hot glue on it instead of twisty ties LOVE IT!
At youtube kipkay made your project thats what mine looks like when you are on youtube put in parablic mic and there you go.
um.. it looks like this but a camo umbrella looks almost like mine ALMOST. I have the same everything but, a camo umbrella and a amp.
images.jpeg
jurtle (author)  Ghost Wolf5 years ago
Glad it turned out well for you. Got any pics? Sound samples?
um my camera is broken but I'm fixing it give me some time
Ghost Wolf5 years ago
Could you use a mic and earphones instead of a plug that you put in the recorder? By the way great job on that, I'm getting the parts now and I just wanted to know.
jurtle (author)  Ghost Wolf5 years ago
You will need some kind of amplification device between the mic and the headphones. Most mics do not have enough of a signal to drive the headphones. The rig shown in this Instructable is intended for both listening and recording. You could make the whole thing much more affordable by substituting an inexpensive Radio Shack microphone amplifier such as the Model: 277-1008. It costs less than twenty bucks. Find it online at: http://tinyurl.com/miniamp That way the set up becomes a purely listening device, maybe just what you are looking for. Just remember that, as with the rest of this project, you get what you pay for. Good luck.
So I could use a headset but, I need an amp >:D
jurtle (author)  Ghost Wolf5 years ago
Yes. You will need (1) a microphone to mount in the parabolic dish, (2) some kind of amp or preamp for the mic, and (3) some headphones or headset to plug into the amp or preamp.
Will that be bulky?
jurtle (author)  Ghost Wolf5 years ago
Just look at the sizes and weights of the elements you intend to use and decide for yourself whether it is bulky or not. It is all relative. One person's bulk is another person's gossamer.
Ok thanks I wanted to know because we have a forest where I live and I play with my friends and I need something to listen on what there saying so I know what there planing. I'm using a camo umbrella hat for stealth.
Could you use a cone collar?(This is not my dog)
360856083_0882190f78_o.jpg
jurtle (author)  Ghost Wolf5 years ago
You have to ask the dog if the cone enhances his hearing. :)
He said yes, he heard a bird six miles away
>:D
InLimbo335 years ago
Could you do this with a lamp shade? A friend of mine, some years ago, made similar thing with a microphone and a lampshade, taping it to his bedroom window. It captured the insects outside remarkably well.
jurtle (author)  InLimbo335 years ago
If by "lampshade" you mean one of those round reflector hemispherical or parabolic things, yes it should work. Just about any roughly parabolic or hemispheric shape will work. The more closely it approximates a parabola the better it is. I am not sure what you mean by taping it to a bedroom window. If there is glass (or plastic) between the sound source and the microphone element, the efficiency of the whole device is compromised or even eliminated. That doesn't mean you won't hear anything. It just means you lose lots of amplification and virtually all of the directionality of a parabolic mic.
audience6 years ago
the mp3 link to hear a sample was completely silent. Do you have another link to listen to a sample? because it looks like this one's not working. It was playing but there was no sound.
jurtle (author)  audience6 years ago
I just checked the link. It seems to be working. Try checking your audio settings to make sure the problem is not on your end. Failing that you can always go to the original site: http://www.bambooturtle.us/ParabolicMicrophone.html. There are some additional audio samples there. I hope it works for you.
j
jurtle (author)  jurtle6 years ago
Sorry for including the period in the url. Try this:
http://www.bambooturtle.us/ParabolicMicrophone.html
posthastily6 years ago
By using the paint-roller handle you can also buy extender handles of various lengths that would allow the mic to be raised above unwanted noise (crowds, etc.) to better target the wanted sound. Also, I've seen postings elsewhere that suggest using a round plastic terrarium cut in half for this type of mic. Apparently the perfectly round halves made of smooth hard plastic work in a similar fashion for gathering sound. The clear plastic allows the user to see through and aim at the targeted sound, and looks more like the store-bought parabolics. Great instructable!
DIY Dave6 years ago
Does it sound bad on windy days?
jurtle (author)  DIY Dave6 years ago
It behaves just like any other parabolic microphone under windy conditions. There is some wind noise that comes from the mic diaphragms. In very breezy conditions there is also some noise generated by the action of the wind on the umbrella itself. If you are talking about a very mild breeze, the foam windscreens that come with the mics work well. Beyond that some more drastic measures would be called for. Maybe that could be an Instructable for another time. As it is presented here, the device is not suitable for windy conditions.
govind6 years ago
Dear friend ,
I'm govind, I red ur project , I liked v much. It is simple n cheap.
Cool it is!
Bye..... Govind
crayzclown6 years ago
c00l
bowmaster6 years ago
You could mount a cheep laser pointer facing outwards so you could aim this thing better.
jurtle (author)  bowmaster6 years ago
Yes, one could do that but it might be a bit of overkill for this kind of device. The "aiming" of parabolic mics is much less precise than one might expect. It is really a little fuzzy. A mic made from a plastic umbrella is even more so. A degree or two one way or another will not make much difference in sound quality. So laser precision is really not necessary. In many nature recording applications you may not even be able to see the sound source. In that case you would not know where to point the laser anyway. Ultimately your ear is the best guide to whether or not you are on target.
wasgij6 years ago
What dollar store did yo get the umbrella from? thanks
jurtle (author)  wasgij6 years ago
It came from a chain called Dollar Tree. I purchased the first one about three years ago. Since then I have gotten a few others, two as recently as last summer. I think the items might be seasonal. You will have to ask. In any case, almost any vinyl umbrella should modifiable enough to work. If you cannot find the exact umbrella hat at the dollar store, try a google search for "umbrella hat." There are lots of sources. Good luck.
balsaboy6 years ago
Who says they are fake?
would this work with a satellite dish? because i have one laying aroud and it s a almost perfect parabole
it all depends on what kind of sound you want to pick up though. If you want the higher, almost shrill, noise, go for a hard deflector like a satellite dish. But to cut that sharp stuff out and get a cleaner sound, a layer of foam or something soft on the inside of the dish would probably take care of that
jurtle (author)  DeLorean49056 years ago
An absorbing surface on the inside of the dish totally defeats the purpose of having a parabolic surface in the first place. The whole thing depends on reflection to operate. A foam coating will dampen all of the sound and reduce the overall gain of the mic. This is probably not a good idea. The frequency response of the device is much more dependent on the size of the dish. If you want a more accurate response on the lower end, use a larger dish.
hmm, i have an old Dish dish (heh, dish dish) lying around in my room... the mic should theoretically be mounted at the focal point of the dish, right? Where all the waves are focused? In the off chance that i'm right here, how do you figure that bit out?
jurtle (author)  Geoffrito6 years ago
Either get the spec sheet for the dish you have, follow the suggestions in step seven of this instructable, or go here. . . . and yes, "fourth" is overkill.
ah, brilliant, thanks!
interesting... I'll have to try this out sometime. seems like the size of the dish would affect the gain more than anything else
that is what its ment for (whell really its ment for satilite signal bouncin but that is why the shape is that way)
jurtle (author)  Oorspronklikheid6 years ago
It will work with almost any approximately parabolic surface. Satellite dishes are probably very precisely parabolic. I have played with one of those from Direct Tv. It does work but because the dish is so shallow, the distance from the vertex of the parabola to the focal point is much longer. It can make for an awkward configuration if you have to mount the mic on a longer shaft. The bottom line is that lots of things will work including woks, plastic dishpans, lighting reflectors, etc. I am thinking that a large golf umbrella painted with some sort coating might be really interesting. Stay tuned
Painting the inside surface with something metallic might be of value if we were dealing with electromagnetic stuff (radio, infrared, etc.). But sound waves probably would not be affected except to the extent that when the paint dried it would make the surface of the umbrella stiffer/harder. Sounds are reflected by hard surfaces and absorbed by soft surfaces (like fabric). Lining the inside surface of the umbrella with aluminum foil would probably provide a harder surface than painted fabric and improve the efficiency of collection. The next step up might be to get some fiberglass cloth and casting resin, and then use the umbrella as a mold.
jurtle (author)  btcarnovale6 years ago
You are right about metallic coatings and electromagnetic waves. But I was not suggesting a metallic coating. You sort of read that into the text. I simply meant some kind of coating to increase the acoustic opacity of a fabric umbrella. Almost anything would do including a basic varnish. My guess is that even a fabric umbrella wet with water would be somewhat better than a dry one for this purpose. Visual opacity is irrelevant. Note that the umbrella hat in the current project is half transparent, at least visually. Once you get into the arena of fiberglass and resin, you have really gone beyond the scope of the inexpensive, easy to build, and easily accessible nature of the Dollar Store Parabolic Mic.
pdub77 jurtle6 years ago
what about the waterproof coatings you spray on tents and jackets? could you spray that to the inside of the umbrella and make it reflect better? it would still be pliable enough to open and close the umbrella with no problem.
jurtle (author)  pdub776 years ago
Those waterproofing coatings are probably not going to affect the relative acoustic transparency of the umbrella fabric very much. Better to use something thicker that will actually create a relatively stiff and smooth surface on the interior of the umbrella. I am just speculating however since I have not actually tried this with a painted umbrella. My guess is that something as simple as a thin coat of Modge Podge or a flexible acrylic varnish might work. If somebody gives it a shot, let us know.
jurtle (author) 6 years ago
Looks like this little thing won a second prize in the Laser Cutter Contest. Thanks everybody! I am looking forward to wearing the t-shirt.
pdub776 years ago
really cool instructable! i have an m-audio microtrack recorder. this would be perfect with that.
shmuley956 years ago
another idea is to plug the mic into one of those 15$ voice memo things, then put headphones into the headphone jack. i dont really know if this would be saving or adding money, because i dont know how much that thing ur using is.
jurtle (author)  shmuley956 years ago
Your suggestion would absolutely save money over the device shown in Step 9. That is an Edirol R-09 digital recorder, way more than $15. Using one of those voice memo things would save money but it would cost in quality. There is no free lunch.
there never is ;-). actually (this is a little nerdy) but i did this and carried around my mac and recorded everything with garage band it came out amazing! (i hid the laptop in a messenger bag of coarse)
nice! that is fantastic! what are you doing with your audio?
where do u get the heads from?! haha
jurtle (author)  xXdyinfaithXx6 years ago
The glass head came from Pier 1. The more realistic one is a beautician's practice head that I found at a local thrift shop. I use it mainly as a head for binaural mic experiments.
llaven6 years ago
Hi, very easy and interesting proyect, could you share some mp3 samples?
jurtle (author)  llaven6 years ago
Your own little Stereo Mic device might fit well with this parabolic. A number of people in the phonography and nature recording communities are experimenting with stereo parabolics.
jurtle (author)  llaven6 years ago
Thanks for looking. There is a sample link included in Step 9 of the instructable:

Here is a link to a short MP3 file that lets you hear how well it works. First you will hear a recording of a growling squirrel with the mic element by itself followed by the same squirrel recorded with the parabolic set up. That is followed by a similar sequence recording a cardinal chirping in the distance, first without the parabolic setup, then with it. The segments are separated by short tones. I think the differences are pretty amazing.

There are other versions of those samples on my website. Look at the original Parabolic Mic Page.
lironess6 years ago
Wow, your dollar store sells umbrella hats! Cool.
canida6 years ago
Looks awesome! You should put a finished picture on the intro page, though. The one from step9 would be perfect.
jurtle (author)  canida6 years ago
Thanks for the nice words! Glad you like it. I took your advice and added a finished picture as the lead. The creepy glass head is included in step 2. I just couldn't let it go altogether.
I would love to see that creepy glass head in all the shots. She makes a nice model. Regarding the project: Very nice. I am going to make one of these with my 9 and 11 year old girls. Then they can spy on their friends and the local squirrels.
darkmuskrat6 years ago
Sweet... (Not gonna ask why the guys heads in the background)