The Consolidated "That Annoying Tone on Audio Channels" Thread [Merged]
Does anyone know why on most 76's Channel 9 has a constant whine that inhibits listening unless you wish to court hearing damage. Sometimes it even bleeds into other channels as on my DEN-IAD flight yesterday. As a channel 9 addict, I find this most annoying.
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The whine you hear is most likely leakage from the aircraft's AC electrical system. Unlike our homes which use 120V 60 hz AC, most aircraft use 110-120V 400hz AC current. The whine you refer to is likely that 400hz frequency, which is the same as the hum you get on poorly grounded speakers or radios in the home.
It's common, and unfortunately not a priority to repair unless it interferes with ATC communications.
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Art234: The whine you hear is most likely leakage from the aircraft's AC electrical system. Unlike our homes which use 120V 60 hz AC, most aircraft use 110-120V 400hz AC current. The whine you refer to is likely that 400hz frequency, which is the same as the hum you get on poorly grounded speakers or radios in the home.
It's common, and unfortunately not a priority to repair unless it interferes with ATC communications.
</font>
Very logical explanation!
I've always found Channel 9 to be somewhat difficult to hear...I've never noticed one aircraft was more difficult than another. I will pay attention now!
Difficult hearing aside, Channel 9 is still awesome!
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I've noticed this twice in the last month SEA-ORD on the three class 763. At first I thought it was just my seat. But twice in a row is suspicious. Very annoying indeed.
But, it was worth toughing it out to listen in on the chaos at ORD on Sunday (July 6th)!
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The whine is much higher than 400 Hz, however, I would guesstimate about 1200 or so. Sometimes it warbles up and down with a small range. It seems confined to the 767 range.
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I was going to post almost the exact same question last month. I had 6 767 flights in a month and they all had this annoying whine. It's just not present on the other channels in any manner equal to that on Ch 9.
I finally trained myself to ignore (block) it and still hear the crew.
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I think you'd be surprised that it was actually 400 hz you were hearing. Otherwise it could be a harmonic of 400, which if as you say would be 1200, makes sense. In either case it is related to the electrical system of the airplane unfortunately.
400 Hz power is easier to convert to DC than 60 Hz power, and the equipment is smaller and lighter. It's been that way with aircraft for over 50 years.
I remember the whine! But I never noticed that it was on 767s primarily. I shall certainly pay attention on that front. If indeed it is the 767, I shall avoid them.
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