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View Full Version : Do start crews headsets cancel noise?


bank_and_yank
28th Mar 2009, 08:57
Can anyone say for sure if the headsets used by start crews should cancel engine noise?

We operate turboprops and the start crews usually use a headset.

When the engines are running there is a muted "engine noise" from the start crew's microphone. Sometimes the start crews switch off their mike and sometimes they do not, but their speech is not drowned-out by engine noise.

I assume that the headsets have a noise-canceling function. Clearly, they need to be able to speak clearly, despite being close to the propeller.

Recently, one of our crews had a problem because the noise of the first engine starting was transmitted loudly into the pilot's headsets.

The start crews say that their headsets are the same as the pilot's, except that the plugs are different.

matkat
28th Mar 2009, 10:32
Ground crew head sets do NOT have noise cancelling. When I did push backs you switched your mic of, when not used.

Rainboe
28th Mar 2009, 11:16
I know what you mean, sometimes the engine noise through the intercom can vary enormously. Just to be clear, you are not talking about 'noise cancelling' as in ear phones. I assume what you are referring to is a sort of 'dolby noise reduction' effect in the ground operator's mike to stop engine noise feeding into the intercom system. This wouldn't be practical- it would end up having to account for quite a large range of engine sounds for different types which would seriously attentuate the ground operators own voice as well! This doesn't happen. I would guess maybe the particular headset was over amplifying sound, maybe the operator was holding his mike further from his mouth to compensate. The effect would be too much engine noise/voice ratio. The only noise cancelling effect to affect you would be the ANR effect in your own earphones.

Kiwiconehead
28th Mar 2009, 12:31
Both Pilot and ground crew headsets normally have noise canceling mics fitted.

Bit of an explanation from Wikipedia
Noise-canceling microphone - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Noise-canceling_microphone)

Usually excess noise is because, in the case of a boom mic, it's positioned too far away from the mouth, or in the case of the DCs with the muff type mic they don't actually seal it over the face.

matkat
28th Mar 2009, 12:49
The only noise suppresing mic I know of is the one with the PTT switch, there again its a while since I did a pushback so I may well be out of touch.

bank_and_yank
28th Mar 2009, 13:48
A typical David Clark M77 mike specification says :-
Generating Element: Electret condenser

Polar Pattern: Bidirectional Noise Cancelling


This makes sense with the wikipedia link above.

In the cockpit, if someone has a dirty mike (holes blocked) there is a little extra noise. Could that explain the extra noise in this case?

What are the DC muff type mikes?

Kiwiconehead
28th Mar 2009, 23:26
What are the DC muff type mikes?

David Clark Company H3312 (http://www.davidclark.com/HeadsetPgs/h3312.htm)

muduckace
29th Mar 2009, 01:17
With smaller aircraft hand signals are probably a better idea. Environmental noise is impossible to cancel out, I am sure there are better models than the the standard D&C. There are two types out there, one with a guard that can be strapped to the face (better and more expensive) and the standard boom mike. I have also found that from aircraft to aircraft the feedback changes as a result of the flight interphone amp. Airbus is horrible, when I was on the line I went to measures of taping the foam out of my old hearing protection to the mic because it was very disturbing to me as well.

The only solution is to ask your operator to provide better equiptment to your ground handeling crew, Maintenance Engeneers or AMT's.

Oh on the boom type D&C there is a little white plastic screw to adjust gain but they are difficult to adjust effectively as the aircraft are also a factor.


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