noice inside the cabine

[vandereydt]

Does anybody know where I can find information about the noise inside the cabine of planes such as the Cirrus SR 20 - SR22-SR22T. Cessna TTx, Beech Bonanza, Diamond Da40-Da42

Thanks so much

Ronny

[Genghis the Engineer]

I doubt that data exists.

If you need it for any reason, getting a sound meter (or if you're less fussy about quality, using a smartphone app) and approaching some aircraft owners and asking if they could help you out would probably be your best bet.

What's your reason for wanting the data?

G

[vandereydt]

the reason behind my question is comfort levels during longer flights

For instance the SR20 I fly in is "less noisy" than the SR22 I flew sometimes in. Wearing the same Bose A-10 ANR headset

But I already had the impression it would be very difficult to find this kind of information. Indeed a noise meter would be perfect
But then I d need to fly in all these plane

thx
Ronny

[Mechta]

Looks like AOPA measure it in their flight tests:

Measured cockpit noise (dBA scale) in cruise at 11,500 feet msl was 88 between the front seats. This is about 4 dB less than most single-engine airplanes.Diamond Aircraft DA42 Twin Star - AOPA (http://www.aopa.org/News-and-Video/All-News/2006/November/1/Diamond-Aircraft-DA42-Twin-Star)

Questions you would want to ask are; was the dB meter calibrated, what frequencies did it measure, was the same meter used for each test, which way was it pointing and was it rigidly mounted or handheld.

Apparent noise level to a person may differ from noise meter readings.

Quite a lot on Cirrus cabin noise here too: Cirrus SR20 (and a bit about the SR22) (http://philip.greenspun.com/flying/cirrus-sr20)

Bonanza here: http://www.aopa.org/News-and-Video/All-News/1998/June/1/Calming-the-Cacophonous-Cabin

DA40 here: http://philip.greenspun.com/flying/plastic-airplanes

[9 lives]

Before comparing the relative cabin noise values of various aircraft, assure that the data collected was consistent. You can alter the cabin noise a lot with power and RPM, so unless this has been accounted for, the data is of little use. Does the noise value you're provided represent the typical cruise you'd like to fly? If your data is for very low power, low RPM, it won't be of much use to you if you'd like to cruise fast.

With a decent headset, I have never worried more about cabin noise, it is what it is, and a quiet jet won't do what I need the plane to do for me!

[ChickenHouse]

Noise inside cabin was measured for some planes, but with the use of headsets and their non-linear dampening especially with ANR versions, I guess the numbers are useless. Total noise pressure will tell u'nothing, i.e. 75dbA at low bass frequency from an O300 will not sound like noise, but the same 75dbA from a Rotax 912 sound like dental powerdrill. Which frequency band your personal noise feeling is triggering at is also changing in time, so what for?

[Rabbs]

Hah - misread the title as Mice inside the cabin...that would have been a good thread!

[Genghis the Engineer]

But then I d need to fly in all these planes

Not really, you just need to persuade some pilots to take a soundmeter along on a flight.

G

[tecman]

The "annoyance factor" is hard to quantify but, to the first order, a decent sound level meter with a dBA weighting (which accounts for the response of the average ear) will help. Unless you get a really bad one, most modern meters based on small capacitor microphones are actually pretty accurate in my experience, at least below 10 kHz. If you can take a few readings around the pilot's head position, then take the average, it'll give you a decent impression. (Strictly, your head modifies the sound field, and you shouldn't average dB..but don't worry too much about it). If you're doing it yourself, or have a really obliging friend, take some dBc weighted readings as well: that gives an idea of the power with a more uniform instrument frequency response.

Typically, there is a big difference between old and new aircraft. Of the spam varieties I can recall, the old Cherokees were shockers. Well designed aircraft using Rotax 912s are actually pretty good, with and without ANR. From personal experience, if I compare a 1966 C172 with an 0-300 with a Tecnam/Rotax P2008, the Tecnam wins hands down.

ANR can produce some odd consequences, too. Just like on commercial flights when your noise-reducing headsets reduce the jet engine noise so that the inane conversations of other passengers more effectively enter your brain, you can get similar results in your own aircraft. My Sennheiser ANR is so effective that I now spend my time looking for hitherto inaudible air leaks around the canopy.