SonexBuilders.net

I saw some mention of this some time back and don't remember a follow up. I have a app on my cell that measures noise level and I pulled it out and measured the level in my Onex with Aerovee cruising at 3000 rpm. It was a steady 79-80 dB. No insulation except for carpeting on the floor.

Thank you for sharing this data. It is actually lower than I expected. It'll be interesting to compare this to inside the electric (and belt reduced) Xenos once Gabe has a chance to record his levels. By the way, which app did you use to measure the levels?

Thanks,
Paul

I can't find a source for it. It's called Sound Meter and I think it came in a list of Tools.

It's pretty easy to find decibel meter aps for your phone but the one I tried peaked out at around 90dB. I checked noise levels using a dedicated meter, only a cheapie so who knows how accurate, and at cruise speed recorded noise levels a little over 100dB. https://www.sonexaus.org.au/galleries/building-tips/cockpit-noise/ 79 to 80dB is lower than I recorded at idle.

Peter

Remember that there is a distance component to dB measurements so comparing values is not necessarily useful unless we know where in the cockpit the meter was held, and whether it was mounted to any surface (which will add in vibration and conduction).

—Noel
(Who used to wrench on race car teams that knew when to briefly lift off the throttle at Laguna Seca, to avoid tripping the stringent noise limit sensors there) ;-)

interesting. i've been concerned about the noise level in my 2012 sonex A with aerovee and straight pipes, since i'm having trouble hearing incoming traffic broadcasts. while that may be a good part a bad ground somewhere, i was still curious. to confirm the noise, my girlfriend had her phone on with a noise app engaged to measure noise level. she held it just above the seat and between the passenger and pilot. it didnt give her a decibel reading but kept flashing 'too noisy'... LOL !

i bought a reasonably priced and higher rated decibel meter off of amazon and took it out to the plane today. i was not up flying long enough to grab numbers at various RPMs while flying. but i did start by getting #s on the ground, all with the meter held at head height about a foot from my MIC and right headset earpiece. i chose this location because thats close to what/where my ear is hearing and the meter is still readable. #s are as follows...
location----RPM--db (rounded)
on ground 1000 103
on ground 1500 105
on ground 2000 106
on ground 2500 112
these are considerably higher than those reported in the URL earlier in this topic, which may be attributable to using different meters and held at different locations. still, my main goal is a reduction of my readings through modifications.

that same URL mentioned attempts to deaden noise on various cockpit panels with sound deadening, to little apparent effect. i still need to capture noise levels inflight at 2500, 3000 (my cruise RPM) and 3200. but in the meantime, i'll be checking here for noise issues and remedies from:
straight pipes,
ill-fitting canopy,
oil-canning,
wind noise,
bad grounds.

all feedback is definitely welcome..........

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.

funflyingguy wrote:and remedies from:

I vote a better headset - ANR or something.

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.

Cockpit noise analysis would be interesting. There are a number of significant contributors. My 912 Onex "seems" loud, but I've never tried to measure it. I'm betting the worst offender is the airframe itself since I used dampers that were a bit too hard for the engine mounts. I'm told that the plane is fairly quiet compared to other GA planes.

ANR headsets should always be used these days, and there are some affordable options as well as the higher priced name brands.

Rusty