Here is a video I made... 32f, motor was turning 4400 RPM's, prop was 3076 rpm's.. tip speed was mach.92......... well under supersonic.. Motor back then had Moroso race mufflers.. they were HEAVY and ineffective.. Plane now has Stainless Steel straight pipes.. no noisier..
You need good speakers and sound card to really hear the true noise/ music the plane makes...
I was well prepared with a smartass comment about a POS camera and microphone, making good speakers and sound card moot....but that really sounded nice
Build a 4-passenger car that weighs 1,500lbs. Then drive it 150MPH. I'm guessing the interior noise level would approach that of our planes. I've driven a 3,500lb car 150mph, and it was anything but quiet.
In cruise in the Cardinal, I think wind, prop and exhaust noise are the biggest contributors to the sound level, in that order. To deal with the wind you need a lot more insulation, a lot more rigid skin, a thicker fuselage and heavier plexiglass with multiple layers. I.e., add probably 800 to 1,000lbs to the plane. Since wind and prop noise are probably the biggest contributors, a muffler will do little unless you solve the first two problems.
What is the interior dB level of an SR-20 compared to a Cardinal? I think the Cirrus is a fair amount less noisy.
I just happen to be reading Bob Gardner's The Complete Advanced Pilot, and he said that "You will always use the same indiciated airspeeds, regardless of altitude." Wouldn't that imply that if Vx is 62 kts at sea level, it would be 62 at 9,000 ft? Your true airspeed would be higher at altitude, but your indicated airspeed would be the same.
An aircraft engine isn't mounted on really soft mounts as auto engines are, mostly because the thrust and gyroscopic forces would move the engine around too much if it was. So more of the mechanical noise of the engine comes into the cabin, which happens (usually) to have the engine mounting bulkhead, the firewall, as the front wall of the cabin. A car has its engine mounted some structural distance away.
That propeller makes a lot of noise, not just from the pulsating airflow but there's a constant roar coming off the tips, too. Bystanders off to the side hear a buzz, but anyone roughly centered behind the prop hears that constant racket. Similarly, helicopter occupants don't hear the whup-whup sound that those on the ground do.
Aircraft mufflers aren't well downstream from the engine. They're right there, getting all that flame, and being shaken to bits as well because they're mounted to that vibrating engine. A car's muffler has some pipe ahead of it to radiate and convect some of the heat away, and it's isolated from the engine's direct vibration. And yet a car's exhaust system would burn out pretty quick, too, if it was being run at 75% power for hours on end.
Some European homebuilders use what's called a "Swiss Muffler" that's mounted under the fuselage and has a long, flexible pipe to it. It exhausts aft of the cabin and that exhaust is often so quiet that at some fly-ins the airplane must be preceded by a pilot car because there's too little noise to alert pedestrians. They use this due to aircraft noise regulations in some of those countries.
Certification costs, of course, are nonexistent. One reason why kitplanes and homebuilts are representing such a large percentage of new aircraft registrations now.
Dan
WOW that's moving!! Imagine flying alone in your new RV and having your doors blown off by a freight trne. LOL..
Build a 4-passenger car that weighs 1,500lbs. Then drive it 150MPH. I'm guessing the interior noise level would approach that of our planes. I've driven a 3,500lb car 150mph, and it was anything but quiet.
In cruise in the Cardinal, I think wind, prop and exhaust noise are the biggest contributors to the sound level, in that order. To deal with the wind you need a lot more insulation, a lot more rigid skin, a thicker fuselage and heavier plexiglass with multiple layers. I.e., add probably 800 to 1,000lbs to the plane. Since wind and prop noise are probably the biggest contributors, a muffler will do little unless you solve the first two problems.
What is the interior dB level of an SR-20 compared to a Cardinal? I think the Cirrus is a fair amount less noisy.
<crickets then returns to wrenching on his certificated spam can>
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That would be totally awesome if 520iS actually existed.
