One of the problems with wildlife video photography is that you can get close to the animal with a telescopic video lens, but what about the sound? It's still far, far away.
Jerald Cogswell came up with a solution. He created a sonic telescope to grab sound and bring it as close to the user as the visual image. Biologists can also use this MEMS microphone to listen to insects and burrowing animals. The microphone can take the sound and match it to the proximity of the image.
Jerald Cogswell mounted a precision MEMS microphone in a satellite dish's focal point so it can feed its signal to an amplifier that enables simultaneous recording and monitoring via headphones.
Yes, Warren, unused dishes are plentiful. You can even find them in trash dumpsters. Mine was one that was left behind when I switched satellite providers. But I felt I needed to give a supply source for those who want something now. But, yep, why pay for it when you can find it free?
This is a creative device. The fact that hobyists can use these technologies in such a useful way is a great thing. There are a lot of mems devices available now, and with the other components that might make up a useful device the scope for creative development is wide open.
Using soundis a good way to find and identify wildlife as well. It is about this time of year that all the sounds come out.
I would think this is also usable in the movie industry. In many cases, it seems that movies are made with microphones on booms that only pick up the sound in the immediate area. That's especially true for nature documentaries, where the camera and sound equipment is often 100-200 yards away from the subject. Very innovative idea.
That might be something I'll try Debera. I'm not sure how that would work but I'm into experimenting. Any references you can provide? The good news is that you can mount this microphone and amp in anything you want. With some circuit board layout it could be made smaller. I'm thinking of redeploying the circuit for other purposes.
I was really impressed with the sound microscope modelling. The dishes are usually found in apartment dumpsters around the end of the month when people move out and don't want it anymore. I will look into the mems device itself, because I can think of some other applications for it. Great article.
Thanks, Jim S. If you build this amp I think you will be delighted with the sound quality. The sound quality of my video was compromised by the cheap voice recorder I was using. But through the Bose headphones, the noise level is inaudible and the sound is very clean; not surprising when you read the datasheet specs of the devices.
Since the article was written I have increased the output amp gain to 20 with excellent results. There are several benefits afforded by the balanced line architecture. Read the MEMS mic datasheet and application notes for tips on making the mic more directional by using an array of them. You could try mounting them in a conventional stethoscope. The MEMS mic's architecture will not give the "proximity effect" of other mics. Proximity effect is the boost of low frequencies when you talk close. This bass boost is used by late night DJs to get that crooning sound. Let me know if you find other uses. You could even use it for a singer's performing preamp if you shield the mic from saliva and dust.
When I was a teenager in the 60's, my neighbor, who was an electrical engineer and a ham, built a parabolic microphone using a small surplus radar antenna. He loaned it to me for a while and I had a lot of fun with it. I put a crystal microphone on it, connected to my toy reel-to-reel tape recorder and I could hear and record whispers from a couple hundred feet away. I imagine a satellite dish, although easily available, would be pretty heavy. I have one in my junk bin from when I upgraded to HDTV. It's too heavy for me to hold in my hand for very long. I would use a tripod for such an antenna. Removing the pole mount would reduce the weight some.
Hi, armoris, I look forward to another Gadget Freak project from you. There's a lot of good engineering savy there. I had two grade school friends who liked to play with my dad's Wollensak tape recorder. They both became radio DJs.
You're correct that removing the pole mount greatly reduces the weight. I didn't have trouble holding just the reflector but a cameraman is busy enough with running the camera action. If he doesn't have a sound person he will want a tripod -- one sturdy enough to hold the reflector in wind. That's a lot of equipment for one person if you are hiking into remote areas so you will need an assistant. It would be interesting if someone who reads application notes would arrange a few MEMS mics in an array to achieve high directionality. They would need to make a custom circuit board but the reflector could be a fraction of the size.
Another idea would be to mount the mic in a pen barrel and use it to find mechanical noise like squeaks. These MEMS mics have been used to monitor the condition of bearings.
It's good to hear from you again and put a face and a name to the handle "78RPM". I might try playing around with those MEMS microphones. I have another Gadget Freak project on the way. It's been submitted for a while and may be the next one. Coincidentally, my next GF article uses a noise-cancelling electret microphone. I don't know if the editor would want me to reveal it before it's published. Yours is a nice project. Keep up the good work.
Thanks for your compliment. Your project requires just as much engineering savvy as any of my projects. I look forward to seeing more from you. I'm guessing that you are a retired electrical engineer like me.
The editor just gave me permission to reveal my next project. It is a "Groan Detector". A woman was referred to me whose husband was stricken with a stroke, such that he is completely paralyzed and can do nothing but groan or make an "aaaahhhh" sound when he needs help. The live-in nurse who cares for him can't always hear him when she sleeps or is away from his bedside. The woman asked me to design a device that would remotely signal the nurse, even if she is sleeping when the patient groans for help, yet reject background noise and music, including the patient's favorite radio program.
I built the device she asked for and sent it to her. She is thrilled with it. I feel that other people, especially nursing homes would find such a device useful.
Not only is this a great project, with an excellent recording and a multitude of other uses, but also, this is one of the few gadget freak things that has worked for me. I have played with sensitive microphones and the usual challenge is background noise, which this system doesn't seem to have, at least not on that recording. Now I need to build one for myself. And yes, those sattelite dishes are available as discards almost every week, if one keeps their eyes open and pays attention.
Yes, Cadman-LT, there are similar products you can buy. Some of them are light weight and made of plastic. But read the customer reviews. Poor quality in most cases, as you would expect for less than $40. Hey, but they only address the sonic telescope. What about that microscopic function, eh? Mount the MEMS mic in a pen.
I had two goals for this project beyond listening to insects and distant wildlife. I wanted to make a truly high fidelity microphone preamp and amp that could be deployed for other uses. The quality through the Bose headphones is amazing. I really think you could use this mic and preamp in a music recording studio. Second, I wanted to encourage hobbyists and engineers to use SOIC devices in their prototypes. I offered an introductory method in the article. Aside from Schmartboard products, you are encouraged to solder smaller components than DIP packages for your projects.
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