Cockpit Noise Level

[Bryan Cotton]

The problem with adding extensive soundproofing to a Sonex is you are also adding extensive weight. Which, if it is too heavy to fly, does reduce the noise a lot.

Our noisy, not too heavy Waiex flew 25+ hours this month. A lot of it with 2 full size adults sitting in it.

[Skippydiesel]

"The problem with adding extensive soundproofing to a Sonex is you are also adding extensive weight. Which, if it is too heavy to fly, does reduce the noise a lot."

I did try to estimate the total weight of my comprehensive soundproofing - from faulty memory, think it may have been in the region of 3kg - hardly too heavy to fly. You could always compromise and just address noise making areas, like firewall, tail cone, etc

It comes down to personal priorities/preference. I intend to tour in my Legacy, spending many days/hours on a trip - any little fatigue mitigating extras will be much appreciated.

[funflyingguy]

and remedies from:

I vote a better headset - ANR or something.

i actually did buy a decent ANR headset from aircraft spruce about 3 weeks ago to use in place of my good, but older PNR headset. it changed the noise i hear, but didnt diminish it much. i best result i have had so far, is to wear earplugs under my ANR headsets. that significantly reduces the cabin noise, but also the intercom and RX transmissions.

today, at the advise of ranier from MGL avionics, i had an electrical tech check my audio plug grounds and my v10 grounds. both checked out fine.

there is a clear and huge increase in cabin noise as i rev through and past 1500 RPMs. thats the point where my MGL v10 seems to no longer be able to squelch the noise, even in conjunction with the ANR headsets.

puzzled for now, but still working on it....

[funflyingguy]

My Legacy has extensive sound proofing - the sticky one side stuff, with a foam core & aluminised outer skin, that comes as a flexible sheet, that I can cut into patterns.

The sound proofing is on the inside of all internal fuselage surfaces, including the under/back of the seat pan, the firewall and the semi bulkhead behind the seat/pilots head.

In addition I have tried hard to seal the canopy by having a close fit and at least 3 sorts of gaskets in play. A gasket pretty much needs to be compressed (at least a little) to work, so where appropriate I have closed cell foam strips, P profile and silicone.

Interesting (at least to me) is the significant change in noise level, when I open/close the two cockpit vents. Much quieter with both closed.

It's not as quiet as my last aircraft, a composite ATEC Zephyr but its not bad at all.

i just bought a product similar to what you mentioned, from amazon. i started installing in a few areas today to see in my next flight if it helps any.

i also know my canopy is a terrible fit, with varying gaps all along the front and back edges. i am looking at V-tape and some foam self-adhesive weatherstripping to help. also considering adding a 'ledge' along the turtle neck at the rear of my canopy, made out of L-shaped aluminum with foam stripping attached, just below the canopy. the turtle neck curve is what i am working out.

i wouldnt worry so much about this except i am often not able to understand incoming transmissions due to the background noise drowning them out. FYI... i've been told my announcements are loud and clear.


i appreciate the ideas....... thanks!

[funflyingguy]

If you can capture a recording, running it thru a FFT will give you insight into whether the noise is driven by the engine or other causes.

sorry, you got me with FFT. what is that?

[Dave Wolfe]

Fast Fourier Transform

Its a tool used to analyze signals. In this case the input would be cockpit noise, and the FFT tool would tell you how much of the noise is being driven by each major contributing frequency.

Engine related items would be at frequencies which are a multiple of engine speed and these show up as peaks on the FFT plot. It will certainly show peaks at engine speed multiples but Im not sure if its good at picking up white noise if wind noise is the primary controbutor to noise.

I think there are some free phone apps that do FFT

https://en.m.wikipedia.org/wiki/Fast_Fourier_transform

[funflyingguy]

thanks dave...... jim

[peter anson]

About 10 years ago I made pretty extensive efforts to reduce cockpit noise. I tried various sound absorbing systems and measured the results with a decibel meter. I wasn't very successful and I was least successful at cruising revs, the engine speed where it would be most desirable to reduce noise. Here's a link to my report on the Sonex Australia site - https://www.sonexaus.org.au/galleries/building-tips/cockpit-noise/

Peter

[Kai]

Just a thought:

If cockpit noise picked up by the mick and broadcast during transmissins is the main culprit- what about using a throat microphone? Some also call this a tactical mick.

As I understand the function of these things, they should not pick up anything save what is produced by vocal chords.

While in ear headsets with a tactical mick are fairly common, I have not found not one general aviation headset with such a device, the main issue might therefore be to replace an existing electret mick, say for instance on a Bose A20.

[Onex107]

Many years ago, I ran across an add to alter standard headsets for unusually noisy conditions like in military jobs. I sent my standard headset in, and they altered it by adding ear plugs, on short wires, to both sides, which I inserted before putting on the headset. Putting the speakers directly into your ears and covering them with the ear cups did a very good job in the Onex. No other sound insulation was installed. I don't remember the name of the company.