Intermittent Hissing in David Clark H10-13.4 headset

Lon33

Lon33

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Lon
I use a David Clark H10-13.4 headset that I purchased new about three years ago. A few months ago, I began hearing an intermittent but loud hissing sound through the headphones. It's been difficult to troubleshoot, because the hiss occurs only when I'm in the air. It doesn't happen while I'm on the ground, not even when the engine is running.

The hissing has occurred in three different airplanes (two Skycatchers and a Sling). And it has occurred when I have been the pilot and when I've been the right-seat passenger. The hiss also can be heard in the headset of my flying companion.

I'm virtually certain the problem is with my David Clark headset, because I have not heard the hiss when I've worn a borrowed headset.

At first, I thought the hissing was caused by the flow of air through the cockpit air vent over my microphone. But the hissing continued even after I pointed the air vent nozzle away from my face and even after I shut the vent completely.

Today, I moved the mike away from my mouth to see if the hiss was caused by my breathing on it, and in doing so, I discovered that the hissing would begin whenever I touched and gently squeezed my microphone, even when it was nowhere near my mouth. This happened only when I was in the air. When I squeezed the mike after landing (with the engine still on), there was no hiss.

I know it's difficult to diagnose a problem without seeing the "patient," but I wonder whether anyone else has had this problem or has any idea what the problem may be.
 
Sounds like noise is just opening the squelch of the intercom from the mic. The 10-13.4 has a very hot mic (my opinion) and will pass a lot of high frequency noise. Try this to see if it's just mic noise... Put the mic in front of your mouth and when the hiss starts, make vowels with your mouth without vocalizing with your vocal cords. If the sound changes, it's just the mic working normally and you'll need to adjust the squelch on the audio panel. The older DCs had a screw to adjust the mic gain but they changed the mic element and there isn't an adjustment on the 10-13.4 mic, I don't think.
 
Nate,

Thanks for your explanation and suggestion. It'll be wonderful, if all I need to do is make a simple squelch adjustment. I was fearing an expensive repair job or even the need to buy a new headset.

- Lon
 
Hope it works out to be that simple.

If I mix a DC with any of the ANR or non-ANR headsets with different mics on them, whoever is wearing the DC has to have the squelch set tighter. On my audio panel, pilot and non-pilot squelches are separate but in newer audio panels from the same company they're a single setting. So if you set them to close on the noise coming from the mic of the DC, everyone else has to basically yell to open their squelch.

Thus my opinion about the hot mic on them. It's not really all that much *louder* per se, but it allows a lot more air noise/very high frequency audio from the cabin into the audio from it than most others. We have about three or four different brands of headsets in the hangar of varying quality and only the DCs need the squelch set much higher.

(In an airplane co-ownership we have piles of all of our old headsets that we all had individually for passengers and old retired models we used ourselves, all lying around on the shelves with a couple of them in the back seat all the time unless removed for load hauling.)
 
I have no direct experience but I've heard DC has service has a good reputation. You might email about it.
 
It's either a squelch issue, your microphone element has become partially separated or foreign matter has locked the diaphragm into a pressured position creating a "hot mic" when the air pressure changes in the aircraft.

Try the squelch, if that doesn't work, it will be necessary to replace the microphone. DC has made a bunch of weird changes to their site, so I have no idea what their "5 year guarantee" covers any more. But the warranty should cover the replacement mic should you require one. If they don't for some weird reason (and I don't see why they wouldn't), let me know and I'll take care of it.
 
Lon33 said:
I use a David Clark H10-13.4 headset that I purchased new about three years ago. A few months ago, I began hearing an intermittent but loud hissing sound through the headphones. It's been difficult to troubleshoot, because the hiss occurs only when I'm in the air. It doesn't happen while I'm on the ground, not even when the engine is running.

The hissing has occurred in three different airplanes (two Skycatchers and a Sling). And it has occurred when I have been the pilot and when I've been the right-seat passenger. The hiss also can be heard in the headset of my flying companion.

I'm virtually certain the problem is with my David Clark headset, because I have not heard the hiss when I've worn a borrowed headset.

At first, I thought the hissing was caused by the flow of air through the cockpit air vent over my microphone. But the hissing continued even after I pointed the air vent nozzle away from my face and even after I shut the vent completely.

Today, I moved the mike away from my mouth to see if the hiss was caused by my breathing on it, and in doing so, I discovered that the hissing would begin whenever I touched and gently squeezed my microphone, even when it was nowhere near my mouth. This happened only when I was in the air. When I squeezed the mike after landing (with the engine still on), there was no hiss.

I know it's difficult to diagnose a problem without seeing the "patient," but I wonder whether anyone else has had this problem or has any idea what the problem may be.
Click to expand...
I know this is a super old thread, but I just experienced the same exact issue with my brand new H10-13.4 headset. I'm a new student pilot so I haven't dialed in to what sounds 'normal' while wearing a headset, but I had the same hiss/static while in the air. I did the same thing and pointed the air vent nozzle away from me, thinking the air was possibly activating the side-tone. Was just seeing if OP, if you remember having any resolution to this issue?
 
@SilverE918, what type aircraft and what radio?

Regarding the OP, it's loud inside the Skycatcher. In the climb, the engine noise is loud enough to break squelch. Dialing down the intercom squelch on the SL40 helped with this.

Some headsets (Zulus for example) also have adjustable mic gain. Sometimes, a transient noise (breathing, or air from the vent blowing over the mic) would break squelch, and I would have to cup my hand over the mic to get it to quiet down. Lowering the mic gain helped with this.
 
Do you have the foam mic cover on?
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Buy here:
 
@GeorgeC, I was flying a cessna 172N Skyhawk, I'm unsure of the exact radio. I can find that out on my next flight.

Thanks for your suggestion, I'll make sure to adjust the radio settings to see if that fixes things. My headset came with the M-7A mic, and from what I read online but couldn't verify on the datasheet, was that the tiny hex screws could possibly adjust that gain.
 
I have to dig mine out of the bag and take off the mic muff to verify - isn’t there a small adjustment screw for sensitivity on that mic? And a “this side towards mouth”?
 
Lon33 said:
I use a David Clark H10-13.4 headset that I purchased new about three years ago.
Click to expand...

David Clark's customer service is legendary. Give them a call on Monday. If you need to send the headset back to them, they should repair it under the five-year warranty.
 
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