what causes the noises that bleed into the headset

SixPapaCharlie

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I hear my strobes, lots of high pitched electrical whining that seems to get louder as power is increased. ANR does nothing for that stuff.

Curious what causes it and how to reduce all that stuff. On long flights it is really irritating.

Here's a 10 second sample of what I hear on takeoff

 
My googleing suggests an alternator noise filter for the whining.
Anyone used one? Do they work?
 
Magic smoke needs lube

ETA: isn’t the plane up for sale? Maybe it knows
 
Magic smoke needs lube

ETA: isn’t the plane up for sale? Maybe it knows

It is but I am still flying it until it sells. Annual is next week and wondering if there is something we can so / install while we have it opened up.
 
You have properly identified the alternator whine (varies with engine speed) and strobe power supply (the "chirp-chirp-chirp-chirp"). You can purchase and install a noise filter (something as simple as a capacitor, at times) for the alternator, and my experience is that strobe power supplies are very difficult to damp out completely. To be honest, I have forgotten about hearing the strobe noise since I replaced my strobes (except for one) with LED beacons, but I never found them particularly distracting.

Likewise, by virtue of the way they work, alternators tend to make a little bit of electrical noise and usually, is not that big of a deal although if it gets much louder, it could be an indication of impending failure in the alternator (failing rectifier).

Consider, for example: https://www.aircraftspruce.com/catalog/elpages/lsAlternatorfilter.php?clickkey=22747 ; or, more money (and thus, guaranteed to work better): https://www.aircraftspruce.com/catalog/elpages/lonestarFilter70amp.php?clickkey=22747
 
That's the flux capacitor warming up.
 
It does seem like alternator whine to me, too. Try turning off the alternator in flight to see if it goes away. -Skip
 
Electrical signal leakage from un/poorly shielded systems? That could be anything in the system, including a power cable that draws more amps under some condition.

Or really good drugs.
 
I think we are going to see @SixPapaCharlie on an upcoming Dateline segment. He's already prepping his defense by citing 'voices in his head.'
 
Every time I skim the Hangar Talk subjects this thread looks like it’s asking what causes a nose bleed.
 
It's called a ground loop. No, not the taildragger sort. A ground loop in an electrical system occurs when the ground side of some part of the circuit is compromised (loose, dirty, corroded connection) and the ground current tries to find an easier path. It "loops" through something else. For alternator grounding, the path is usually via a cable that runs from the alternator to the firewall, and from there to the battery through the airframe. Aluminum airframes tend to oxidize and resistance builds wherever a terminal is grounded to it, so the current will trickle through other stuff and find its way, for instance, into the headphone jacks where they're grounded to the panel and through the intercom circuitry to internal ground points. It only takes a tiny bit of that rippley alternator current to cause that whine. Headset jacks should be insulated from the panel with special insulator washers and a ground wire run from it directly to the avionics ground to remove that path.

Fixing strobe noise is harder. One has to get under the panel, with the master on and the strobe running, and while wearing a headset, and start wiggling grounds and tightening grounds screws and so on. Sometimes fooling with a jumper wire from ground points to the radio stack can find a bad ground. I once did this with a particularly stubborn alternator whine by taking the cowl off, alternator belt off, and pushing a tablesaw up close to the engine and running the alternator with belt off the saw's motor. Saw blade disconnected, of course, then getting under the panel and so on. Found that the intercom box, a portable affair, had been screwed to the 172's metal pedestal structure above the fuel selector, and the metal case of the intercom was grounding the headset jacks in it. I pulled the screws out and fastened it with Velcro instead. Whine was mostly gone. I also found that a jumper between the upper and lower sections of the firewall cleaned up the rest of it. The rivet line between those sections was oxidizing and forcing the ground current into various undesirable places. I ran a light ground cable between those sections. The alternator was grounded to the upper section, the battery was grounded to the lower section. Easy to see that any resistance between those will deflect the current all over the place in the airplane.

Old airplanes are fun.
 
interesting. Mine looks a hundred years old. Also has a Cessna logo on it.
Yeah, but throwing parts at it in the hope of curing it is an expensive way to go. Too many mechanics do that. I have fixed several whiny airplanes, and not once was it the regulator.
 
Curious what causes it and how to reduce all that stuff. On long flights it is really irritating.
Can be a number of causes but usually its bad wire grounds/connections and/or failed wire shielding. One route to find the cause is to try and isolate the circuit by turning it off/on via a switch or circuit breaker while the aircraft is ground ran. While the various types of noise filters can work they’re usually specific to a certain “frequency” and may or may not work. I had better luck wringing out the wires after isolating the possible cause than installing filters. May want to try the isolate check before start the annual then when opened up for the annual you can chase the wires. This can be a tedious thing to fix especially if the airframe ground plane is not continuous.
 
Are you sure its not your passengers screaming in fear?
 
Part of the plane is wood, right (spar)? Less material and more chance that corrosion between sheet metal overlaps and rivets/ribs contribute to grounding issues. As stated above, make sure electrically noisy equipment is well grounded.

Also check your radio and intercom shielding (proper shielded wire, and properly grounded shield).
 
Part of the plane is wood, right (spar)? Less material and more chance that corrosion between sheet metal overlaps and rivets/ribs contribute to grounding issues. As stated above, make sure electrically noisy equipment is well grounded.

Also check your radio and intercom shielding (proper shielded wire, and properly grounded shield).

Wood Spar????
Heck No!

They built these things around sewer pipes.


maxresdefault.jpg
 
Start by checking the headset jacks, then clean the ground on the engine mount, then check clean grounds for avionics.
 
Wood Spar????
Heck No!
They built these things around sewer pipes.
Is there a ground wire between the wing and the fuselage? Or are they relying on the spar and drag spar bolts? You could chase the strobe noise by sticking a jumper between a bare spot on each wing (screw head, maybe) and a similar spot on the fuselage, while wearing the headset and having the strobe on. If the strobes are in the wings, that is. Tail strobe is much harder to catch.

But ungrounding the headset jacks from the panel is one of the primary, first-off things. It's the one thing that avionics guys do just because it should be done anyway.
 
Might, but some LEDs create their own noise. Better to find the problem and fix it.
I hear the strobes firing but it's not loud enough to bother me. LED's might go in for other reasons (cracked socket, 3lbs of ballast, etc) but I was wondering whether or not silencing the strobe noise would be a pleasant side effect.
 
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You know... the Aliens guy looks a lot like @Tantalum .... That's crazy!
 
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