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What is that sound on 777-300er?

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I flew on EVA air 777 often and there is an sound that always puzzles me. Video reference can be found here (

). At 2:50, you can hear the high pitch sounds twice. I remember I heard the same sound on other 777W for other airlines on YouTube but cannot find them now. Any idea of what it may be?

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Engine startup. Usually left engine first, then right. The PMDG does the same if you start it up from cold and dark. The beginning of the video reminds me a lot of X-PAX as it also shows passengers boarding, then in the cabin during flight and then deplaning.

 

Best regards,

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Engine startup. Usually left engine first, then right. The PMDG does the same if you start it up from cold and dark. The beginning of the video reminds me a lot of X-PAX as it also shows passengers boarding, then in the cabin during flight and then deplaning.

 

Best regards,

 

Thanks Jim, but I don't think that it was the engine startup. I am talking about the very subtle high pitch sound at exactly 2:50 of the video before engine startup. It only last for like...2 seconds, and it sounds like siren to me. Trying to find another video having that particular sound.

Thanks Jim, but I don't think that it was the engine startup. I am talking about the very subtle high pitch sound at exactly 2:50 of the video before engine startup. It only last for like...2 seconds, and it sounds like siren to me. Trying to find another video having that particular sound.

 

Found another video at 5:40 and it lasted for 1 second, the siren like sound.

 

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Hi!

I know what sound you're talking about. I've been on several 777s in my short 16 years of life, but I know that sound. I've also heard something similar on A320/321s, but it was louder and sounded like a dog. I always assumed it had to do with hydraulics. I've asked a flight attendant on a JetBlue flight (so did my mom... she thought there was something wrong with the plane  :lol: ), but they all said it was a common sound and they themselves never knew what it was.

I did some research and here's what I found:

http://forum.avsim.net/topic/291904-boeing-777-high-pitched-whirring-noise/

http://www.askthepilot.com/questionanswers/the-barking-dog-airbus-noises/

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The "barking dog" is a hydraulic related sound. The sound the OP pointed out, as I mentioned above are engine ignitors. These seem to really stand out on the md-80 series JT8D engines. If continous ignition is selected, these can be heard until the overall operating sound of the engines drowns them out.

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Ar! engine ignitor it is! A quick search on md-80 engine ignitor comes up with this

 

 

It really does stand out here. I am also wondering why not all videos have that sound. I am assuming all engine starts require the ignotors, and for those videos which have that sound, they all start at different time.

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Interesting. I have never heard this sound in my life, and I've flown in A320s, B777s, and B737s (Do they do this sound also?). 

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Interesting. I have never heard this sound in my life, and I've flown in A320s, B777s, and B737s (Do they do this sound also?). 

 

The A320s don't have this sound as far as I know, but they do have the infamous "barking noise."

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Interesting. I have never heard this sound in my life, and I've flown in A320s, B777s, and B737s (Do they do this sound also?). 

 

I hear this sound every time I am on 777W, and they are pretty audible. But it seems there are not many topics on this as far as I know.

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Ok I have done more research on the topic. The sound should come from the ignition capacitors recharging after each fire. When the capacitors recharge, they sometimes interference with the PA system so you can hear it through the cabin. And apparently, it is not always there, and that explains the randomness of the sound.

 

Let me know if I am wrong.

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