parabolic microphone

[mikeg 0]

I need to make a parabolic microphone to record shot gun blasts from 500'- 2000' and have them record on my cctv system.

 

My first attemp was a 18" sat dish w/ a sheet metal shroud. I used a Dynamic microphone rca #F-V100- frequency 100mz-10,000mz

sensitivity 59db, output 300ohms unbalanced.

 

It did record the shots last night but not as good as my ear heard it in my house.

 

somewhere I lost allot of sound, any ideas???? thank you and please respond, If YOU HAD NOT GUESSED IT ALREADY,THE RECORDING WILL BE TURNED OVER TO THE POLICE AND WILDLIFE. they need a time/date pattern. thanks

[Jasper 0]

The good ones are expensive.

 

The Dan Gibson Parabolic Microphone has the reputation as being the best available. Pricey though. Can hear a conversation at 400 feet though.

[JMANOFNVS 0]

I just want a sample of the shot gun blast once you get it down. Think it would be great for my door bell!! What Audio companies have you called for answers if any??

[mikeg 0]

I was hoping to build one, not for the cost but #1- I will install this was in the woods the weather can ruin it, #2- kids can ruin it, #3- the illegal hunters will most certain shot it.

 

If I buy it I would have to tare it apart to record from 3a.m.-9a.m. no unit can do this. So I must build it.

 

I Really need a good mic. The dish will be a s/s 24" wok or salad mixing bowl, they are smooth and very deep (perfect) It,s the mic I no nothing about. db's, etc.

[Jasper 0]

Many of them have recording jacks out the rear of the units that you can hook up to a tape recorder. If you can find a recorder that has the timer function that will work. I have even used the Voice activation systems on them as well. That would not help unless they did two shots back to back.

 

I have done continous recording using a seperate timer, but this was indoors pointing out. No exposure to weather conditions.

 

The weather is a whole different issue. You will hear everything. And the sensitivity of the microphone will most likely be affected in a negative way as well. Water droplets on it will affect it and any other debri that may collect on it. And of course you have to worry about the electronics of everything involved in order to accomplish this task.

[JMANOFNVS 0]

Oh I see your mission now. So have you talked to any audio companies at all at least for some ideas??

[Jasper 0]

That microphone you used, is it a directional type or omnidirectional?

[JMANOFNVS 0]

Have you tried one of those Bionic Ears they use for hunting??

[Jasper 0]

I have one of those. There not very powerfull.

 

Nothing like what he is talking about building. He wants to hear real far away.

 

That microphone you are using is really cheap and the wrong type.

 

Anyway let us know how it turns out.

[mikeg 0]

This is a mission.

 

I went out and bought 5 differant microphones.

 

Each one sounds differant then the next one.

 

So I tried to install 2 of the best microphones togeather double the pick up right? wrong----- one always would not work??? strange?

[Jasper 0]

You need a powerful directional microphone. Their fairly expensive.

 

I think you have probably done this, but to make sure, you have to point the microphone towards the inside of your dish or bowl.

 

You can find information on the internet on how to build your own parabolic Mic if you haven't done so already. The microphone is the most important part though. The other mic you had was omnidirectional, which it shouldn't be. You need a directional for best results. Plus that mic was very cheap, intended for very close up vocals.

[mikeg 0]

Yes it is pointed towards the dish.

 

I completely understand the weather elements, I am looking for as many days (Sunday a must) before the dish is found or ruined.

 

I thought because the echo of the gun fire is loud, It would be so easy to record with a dish/bowl.

 

I will also try differant wires on saturday, to bring the dish 100-250' into the woods and see if I loose any audio signal.

 

I was also thinking of a wireless mic but the woods and trees would block the signal? no line of site! I learned that with the cameras!

[Jasper 0]

It can be done. But it costs a little bit of money unless you do everything from scratch, which means you need to really understand how it all works together.

 

Here are some links I ran accross. Hopefully there will be something in those to help you out.

 

Principals of a parabolic microphone

http://www.madsci.org/posts/archives/apr99/923344961.Ph.r.html

 

A guy building his own from scratch

http://www3.telus.net/chemelec/Projects/Parabolic-Mic/Parabolic-Mic.htm

 

Specialized microphones

http://www.pimall.com/nais/e.mic.html

 

http://www.amazing1.com/accoustics.htm

 

The main problem I see here is the budget. But if you can get it close enought to the source than you don't need as powerful of a microphone. It can be done, but it all costs more money.

 

Also need line of sight for the parabolic microphone as well for best results. When I have used them you still have to point them in specific direction. You can't just place it somewhere an expect it to pick up noise in a 360 degree redius. Maybe try pointing it in different directions.

[JMANOFNVS 0]

I have been all over the internet too and agree with Jasper. Building your own is the way to go. I also seen one site that mentioned an amplifier will help boost your incomming signal. There was also a couple of site about a college group that built one. If you haven't searched the web..try it.

[Jasper 0]

Oh. On my Bionic Parabloic Mircophone, if it hears a sound that is too loud it shuts down quickly and then comes back on. I don't know how yours is built, but that is what the Bionic Microphone did to me when wearing the amplified headphones that came with it. So maybe your just catching the echo of the shot?

 

Just pulled it out to look at it. Looks pretty water resistant too. It has a plastic stop tab on it to allow it to be the optimum distance from the dish. It looks to be close to (edit) 2 inches from the very center of the plastic dish.

 

It has a built in amplifier in the microphone.

 

Keep us updated on your progress. It is a good project.

[mikeg 0]

last night I used a better microphone and it did record allot better but not what I needed.

 

I tried to install a amp last night all I got was hum.

 

Today I ran 200' of #18 wire (door bell wire) got mostly hum.

 

I then ran 200' of cable/sat rg-6 wire, no hum at all.

 

Putting the parabolic microphone in the woods really helped with no more background noise. quiet as a mouse.

 

I will cross my fingers, 13 more hours to gun fire! time.

[Jasper 0]

Your persistent. That's good.

 

You'll know a lot about parabolic microphones before this is all over.

[Gesualdo 0]

OK, Got a different idea for you. If you can get to where you think the sound is coming from without the bums finding out about it, how about setting a hidden(descrete) microphone there wired to the parabolic lens above to transmit to a location and pick up the signal from there. maybe trim some branches to aid in distance along the focus. may also help to put the bums in a recordable set position as they shoot the parabolic transmitter. And you can rest asured that the sound will be transmitted before the thing is destroyed. Probably loose the mic and let them know who recorded them but it may be worth it to you. Just a thought.

[mikeg 0]

Problem is these are 2 sq miles of heavy wooded woods.

 

They hunt deer from 3-8 a.m. almost every night.

 

wildlife officer came out once and they did not shoot. surprise huh!

 

So I plan to hand over one weeks audio/video tapes with a pic of the days newspaper at the end of the tape to the police.

 

The sound recording will prove night time hunting which is illegal.

 

Each day a police officer buddy will turn on my recorder and remove the key. he will come back the next day remove the tape install another remove key again for 7 days.

 

The police will have to call wildlife and put pressure on them to find this guy

[mikeg 0]

Recording was poor again, I am trying Radio shack# 33-3022 tonight to test this preamp mic w/ a condenser mic, this has a very low frequency response.

 

If this fails I am buying a mixer/amp/preamp unit. then I can play till I get it.

[Jasper 0]

If you are going to use that microphone maybe you should elminate the dish? It is another omnidirectional mic. My understanding is that you should use a directional microphone and the dish will collect the surrounding sounds and focus the sound to the center of the dish where a directional mircrophone will work best.

 

You probably have researched this more than I have by now? Isn't that microphone kind of defeating the purpose of the parabolic dish?

[rory 0]

deer hunting

[Jasper 0]

You’re definitely going to need an amplified microphone for best results. Big, Big difference.

 

Good link for construciton info.

Another Home Made Parabolic Mic (stereo)

http://www.solorb.com/elect/misc/bige/

 

another link:

http://www.bio.umass.edu/biology/kunkel/gjk/microphone.htm

 

 

How about a picture of what you have created so far? It would be interesting.

 

What pre-amp are you using?

[Gesualdo 0]

You definitely need to use a directional mic with a very high gain to get any kind of distance also the mic would need to be directly at the focal point of the dish used to maximize the input to the mic and the parabala of the dich needs to be correctly shaped to focus all the sound at the specific point where the microphone is. a salad bowl in generally not designed for this and calculating it is not easy. some of the sites listed may provide more information. Have not looked at them myself yet. Interestingly the discovery channel just did a program that addressed a light gathering and focusing parabolic lens. With several microphones already in hand can you create an arc of parabolic mics to pick up a larger area since they need to focused at a specific point. 2 miles of dense woods is a lot to cover. wouldn't any shots at that time warrant an investigation or are the mics not picking up anything?

I don't think radio shack will have what you need.

[Jasper 0]

That microphone you got from Radio Shack has been discontinued.

 

I can't find any specs on it. You should be looking for the highest +db gain mic you can find for your money.

 

I think you will be wasting your time with that mic tonight unless you are using a amp to boost the gain. Like +40db to +120db gain.