Throat mics

Mike G

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Does anybody have any experience with throat mics and radios like the Icom A6?

I have a VOX intercom and the rear passenger (its a Magni M16) mic keeps switching on and off with engine and wind noise. I flew helicopters in the RAF (as in Royal Air Force) 30 odd years ago and we had throat mics that seemed very effective has any one tried this in a gyro?

Mike G
 

Racer

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My hanger mate Thomas and I are trying to find a throut mic that will work well, We have bought a few off E-Bay but have not had very good results yet. Could just be a "You get what you pay for" thing. May have to just spend the $$$ and get a quality unit. When we find something that works well I will post here for you.
 

PW_Plack

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Mike, these things generally sound bad when used with many common radios. I think it may be partly an issue with the frequency response of the radio.

A throat mic (or those awful ones that put the mic in your ear canal) will lose much of the higher audio frequencies essential to understanding consonants in speech. If the radio does not sharply cut low frequencies to balance this effect, you sound like you're talking through a pillow.

Engine and wind noise both have lots of low-frequency energy, and your neck and chest make a great resonator. Limiting the low-frequency response of the radio's mic input would help there, too.

The ear canal mics are especially bad at boosting the frequencies at which your head resonates, making it sound like your talking through a paper-towel tube.

The quick, dirty way to cut lows is to insert a series capacitor in the "hot" lead of the mic audio, but finding the correct value requires knowing the impedances of the mic input and the mic itself. Also, a series capacitor will block DC, so if it's required as part of your push-to-talk scheme, it will create a problem.

Modifying the radio's internals is often the most elegant way to alter frequency response, but it's (a) difficult with the new surface-mount components, (b) risky to the radio's reliability and resale value, and (c) illegal in a certificated aircraft, and could cause illegal out-of-spec transmitter operation in ANY aircraft. In short, this should be designed, not "hacked."

These alternative mic types are becoming more popular as the use of MP3 players, digital cellphones and bluetooth earphone/mic sets lowers our expectations for audio quality. This stuff matters when you fly. There may come a time your life depends on being heard and understood clearly. If it means a slightly less convenient mic that's located in front of your mouth, it's worth it, IMHO.

Most people test mics by going flying and getting reports from other pilots. They'll usually be overly polite, when in reality your intelligibility is severely compromised. You should go flying, and leave a recorder fed by a radio on the ground, so you can listen to your own audio when you get back. If you do, you'll probably be shocked at how bad these things sound on most radios. If you conduct an A/B test with a properly positioned boom mic, you'll probably hear so much difference you won't want to fly with a compromise.

As someone who deals with audio professionally, I'm discouraged at how new technology is not used to improve communications effectiveness. The state of the art seems to have peaked sometime in the late 1970s...since then, it's been all about cutting costs, bandwidth and physical size.
 

Racer

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I am all ears on a good alternative.
I have a mic that is in front of my mouth but it picks up alot of engine noise. I have reduced the wind noise to an acceptable level but the engine noise is the main problem I have now.
 

All_In

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I'd liked to know what mic is the best also?
 

helipaddy

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I fly with a full face motorcycle helmet with the mic held in with a ty-wrap and a lead that has a socket for a set of normal in-ear earphones. its connected to an Icom A4 that i fiddled with to get a bit more output power. there is little or no wind noise and the comms are crystal clear.

Try taking off the foam windsock and put a bit of tape around the front of the mic where the wind will be hitting it, then put the windsock back on. Most Electret mics (dave clark M7 and peltor) have holes both sides of the mic which helps a bit to cancel ambient noise in a cockpit environment but the mic doesn't work really well with 60mph of wind blowing into it
 

Mike G

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Paul
Thanks for some interesting input, I might try your idea of recording myself when flying, with and without the Helipaddy tape over the mic.

It will have to wait till I get the rotor back on.

Mike G
 

helipaddy

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Here's the front and rear of a Peltor electret Mic. cover up the back of the mic with some tape and it should make a difference
 

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fiveboy

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HeliPaddy

Why would it be the back of the mic (I assume thats the side facing your mouth?) and not the front (the side facing the wind?)... or have I understood the front and back in reverse? The noise cancellation for cockpit explanation is an elegant one.

Just wondering.
 

Racer

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I already have the back of my mic taped up and that did help the wind noise problem, It is the engine noise problem now that I am having to deal with.
 

helipaddy

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Fiveboy, Sorry, put the tape on the side you don't talk in to!

Racer I've found that in extreme noise that if you tape up both sides of the mic then put a little slit in the tape on the mouth side of the mic that helps most of the time
 

All_In

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I noticed Ron Awads mic was completely covered with leather.

I don't remember even seeing a hole in the front of the leather covering.

The intercom was clear as a bell, and I was very surprised there wasn’t any wind noise while flying open frame. (Going slowly deaf may help here)

Maybe Ron will comment about his setup?
 

ckurz7000

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If you have problems with your VOX cutting in and out intermittently, have you tried the simple and obvious thing? I use a Filser ATR500 radio/intercom and -- like most of its ilk -- there's a setting that allows you to adjust the mic sensitivity and VOX sensitivity separately.

First you adjust the mic sensitivity (actually the sensitivity of the mic input on the radio) so that your voice comes across as clearly audible with everything else (like VOX and volume) set to a midpoint value.

Then you adjustt VOX starting at a low value and going gradually upwards (to less sensitivity) until the intercom cuts out. Then I go one notch further and leave it set there. If it cuts in too often during flight, I turn it up one notch.

Of course, if the rear seat passenger sticks his head out the side so that the wind hits the mic directly, no amount of VOX will be sensibly able to correct for that. But I can fly 99% of the time with the intercom only cutting in when someone is actually talking.

Since VOX is easy to adjust on my radio, I find using a setting of VOX=2 (high sensitivity) on the ground and VOX=4 (lower sensitivity) up in the air works best. That way I don't have to yell so hard when on the ground.

-- Chris.
 

Bill Clem

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The often ignored cause of poor radio communications...

The often ignored cause of poor radio communications...

I'll try to make this brief because it is a problem that I have dealt with for 12 years. When I built my Dominator, I chose a Terra radio because it's size was perfect for the panel. Afterward, I kept getting complaints that I was "unreadable". The gyro spent a week in the avionics shop and received a metal ground plane and 5, that's right, 5 filters. On the mags, in the power supply and other places I can't even remember. The clarity of the radio transmissions was better, but still, particularly when the engine rpm's were high, others had trouble understanding. And no, the spark plug wires are well away and on the other side of the engine from the antenna. In desperation, I bought a small sound meter, it measures sound in dB's. As I recall the threshold of pain is about 110 dB. And those Electret mikes have a noise canceling capability up to about 108 dB (don't quote me, look it up). So I went flying with the sound meter and measured 132 dB next to my helmet!! As I recall, an increase in 10 dB is a doubling of sound energy. I tried the throat mikes and the ear mikes, both were muffled, to say the least. I tried the foam cover, the leather sack, and then built a mike muff of closed cell foam with open cell foam toward the mouth. It worked fairly well. But the best solution was designed by Dick Goddard, taking an ear protector cup, installing the mike inside so the whole thing fits on the boom. Works very well and greatly reduces the ambient noise.
 

PW_Plack

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As I recall, an increase in 10 dB is a doubling of sound energy...

Bill, 3 dB is a doubling of the energy. 10 dB is ten times the energy!
 

Mike G

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Bill
Any chance of a photo of your final solution?

Mike G
 

Bill Clem

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Sure, but it'll take a couple of days. And I'll have to figure out how to post a picture. But it simply is a hearing protector cup that has a hole drilled in the side, a rubber grommet installed and the microphone, attached to the boom, is forced through the grommet into the back of the cup. Looks kinda weird. It is similar to the rigs used by carrier deck crews on aircraft carriers, although they use straps rather than a boom to the helmet. The key to telling how well it works is to listen to the sidetone, that tone that is sent from the mike, back to your ear cups. If you sound clear to yourself, but the transmission is garbled, then it is likely RF interference or a problem with the radio. If you sound scratchy and garbled to yourself then the the problem may be ambient noise.... or your voice.
 

Mike G

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Bill
My mic seems to work OK, the sidetone is is loud and clear, my problem is with the passenger in the back (it's a tandem Magni). I have tried all adjustments of the voice activation system on my softcom intercom and no setting seems to be good. I turn it down for take off because the engine noise switches it on and the noise is terrible. This isn't a good idea since I want to hear if my passenger has a problem during the take off especially if they've never flown an open machine before. I then adjust it during normal flight but can hardly hear my passenger and his mic keeps turning on and off with either wind noise or the Vox is picking up enough engine noise sporaidaclly to swith itself on and off. It's a real pain.

Mike G
 
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