I just read a claim that a 4-blade Marquise was quieter IN THE BACK than a King Air 200. Can anyone support or refute this statement? I find it surprising.

I've seen MU-2s with headset/intercom stations in the back, but I have never seen a 200/B200 with them installed (except for a single installation so the chief passenger could talk directly to the pilots without walking forward.)

The Marquise came with improved factory sound proofing and is reasonably quiet in the back.

I would also be skeptical it is better than a King Air 200, however.

Most Marquise passengers don't wear headsets.

Only way to be sure is to measure it on both planes with the same meter configured the same way.

MU2s seem way louder on the outside than on the inside for some bizarre reason.

Mike C.

I've ridden in a KA 200 a couple times and owned a Marquise. I would say the cabin noise levels are comparable. Maybe the Marquise was slightly quieter, but I didn't notice a big difference. On the other hand, I definitely don't think the cabin noise level is higher in the Marquise, compared to the King Air 200.

I have a sound meter I'd be willing to lend out if we can find two willing owners

Or, they aren't that expensive

https://www.amazon.com/Digital-Classroo ... g=btalk-20

I drive the Marquise, F model, and KA350i. I realize the 350 is not a 200 but it's a start.

The 350i is the quietest and smoothest by far. 75 dBa in the back on decibelX iphone app.

Marquise is louder by almost 10 dBa but gets louder between props. We have 10k of additional insulation installed. Sadly, I don't think it made a difference. I wouldn't do it again.

The F model is louder yet (especially in the cockpit, but you mentioned passengers).

I have a decibel meter in the garage at home if we want to get scientific and can hitch a ride in the back of a 200 or 250 on the field.

What's consensus on weight scale to use? A or Z?

There is a huge difference where in the cabin you measure, what props you have, what altitude, etc.

We're nearly 90dbA in the cockpit, over 10 less than that in the third row, but that can vary +/- 5db depending on the height, how close to the sidewall you measure, how close to the center of the window you measure, the phase of flight, etc. All consumer sound measuring equiment seems to read differently also. I use my Apple Watch, which differs from the old Radio Shack db meter that I have.

Garret aircraft have a bad reputation simply because they are very loud on the ground compared to a PT6 and that's where people (who aren't on the plane) hear them. In flight they are no louder or quieter than a PT6, all other things being equal.

I'd say there are three classes of airplanes, loud (GA aircraft wit a prop up front, mid80s db and up) here a headset is a practical necessity, medium (80 to low80s) where a headset is not worn by passengers but required for the pilot), and quiet (upper 70s down, jet aircraft where an around the ear headset is not needed). These would be average numbers around where your head is. I wandered around the 340 and got anywhere from 81db to 92db as the quietest and loudest readings waving my wrist around different areas. Maybe 86 is a good average. Headsets wanted by passengers but not strictly required.

Loudest I have seen on my watch in GA aircraft is low 100db in a helicopter to 78 in an older large cabin bizjet, but that varied also. I can't remember what it is on commercial jets, I think upper 70s also, but I was on a JSX RJ and it was very loud for some reason. I'm flying on a Lufthansa A350 in a few hours I'll post what that is, as a new widebody I would expect that to be about the quietest.

For a data point - aerostar 601P center of cockpit in cruise flight.

I can’t edit my previous post any longer, but the A350-900 I am on is about 71db in my seat according to my Apple Watch. It was 80-81db during takeoff and initial climb.

John, how does the 441 compare to the 340?

Garrett turboprop engines idle on the ground much higher than comparable PT-6's. If you ran a PT-6 up to those same speeds, they sound just the same. Once in flight, or for that matter on the ground inside the aircraft, I think they're comparable. It has much more to do with make / model / placement of the props on a given airframe.

I had a Merlin IIIB - Garret -10's with the low RPM 4 blade Hartzell props. Inside it was surprisingly quiet, but I would occasionally fly in a Merlin IIIA that one had the older -3 engines converted to -10's, but retained the old 3 blade 2000 rpm props. Without a good ANC headset you'd want to slit your wrists after an hour it was so loud inside. The IIIB was quieter inside than our Falcon 10.

I thought the reason the MU-2 was so howlingly obnoxious on the ground outside was the fact that the engines were mounted in the underside of the wing, placing the exhaust in a spot where the sound would resonate between the ground and the wing, probably compounded by where the prop is, etc.

In my Aerostar 700 series, I would sometimes use 45% power for ultra long range cruise (yielded about 200 KTAS), with the props at 2000 rpm. It was incredibly quiet in the cabin at that power setting up at altitude.

I experienced the same lack of improvement when I installed a lot of "sound proofing" in my Marquise many years ago. You can't reduce the sound coming through the windows and there is usually a window in line with each ear in the plane A dog laying on the floor might benefit but not passengers sitting next to windows. Once the sound coming through the windows is the same as the sound coming in elsewhere, you are probably just making the plane heavier by adding acoustic insulation

what app are people using on iPhones? Seems we could compile some interesting data if everyone was using the same app, preferably on the same model phone.

Good question. I’ve been using the free NIOSH app from the CDC. iPhone 11 Pro.

here's my C90B, apparently as quiet as an airbus A350 on takeoff/climb?

if you are going to use an iPhone meter, they are prone to error from wind noise since the mic is not protected, be sure to close all your fresh air vents when taking readings, I found it too error prone so that's why I bought the standalone meter

it was more consistent

Great looking KA, Brian!