News:


  • March 28, 2024, 11:32:58 PM

Login with username, password and session length

Author Topic: What is the source of the noise?  (Read 7977 times)

Offline frank mccune

  • AMA Member
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1621
What is the source of the noise?
« on: July 25, 2015, 03:13:33 PM »
    Hi All:

    What is the source(s) of the noise generated by our i.c. engines? Some contend that it is generated by the exhaust and some contend that it is generated by the prop.

    As you may have read, we are having a noise problem at out field.  Some contend that it is only the prop noise generated by the F2D planes that people object to but I think that it is the exhaust noise, close to 30,000 rpm, that produces a high frequency exhaust tone that upsets the neighbours.

    We did not have noise complaints until the F2D planes began using our field.  We ran all engines sans mufflers in all sizes without complaints but now!

     I think that we are going to have to resort to using mufflers in order to keep our field! A few members are resisting the change, but the alternative is unthinkable. 

     What are your opinions? Is it exhaust, prop, or both?  Is there a thing as a quiet prop?  Electric flight AAAAAAAAAAAAAAAARRRRRRRRRRRRRRRRRRRRRRGGGGGGGGGGGGGGGGGGGGGGGG Lol

                                                                                       Be well my friends,

                                                                                       Frank

Offline Ron Cribbs

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 330
Re: What is the source of the noise?
« Reply #1 on: July 25, 2015, 03:29:23 PM »
Both.

More so the combustion than the prop.

Ever had a shaft run? Pretty loud

Ever heard an electric? Pretty quiet.

My thoughts, others may vary.

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12804
Re: What is the source of the noise?
« Reply #2 on: July 25, 2015, 04:09:24 PM »
What Ron said, mostly.

Electric stunt planes are pretty quiet, but there are some props that are known to be loud.  Electric speed planes can be LOUD, at least based on my YouTube viewing:

.

Basically, engines are loud and need mufflers -- with exceptions like diesels.  Propellers are mostly quiet -- with exceptions, mostly when the tips get close to the speed of sound and generate little sonic booms that hit your ears at twice the engine RPM.

Your best bet is to get a sound level meter and put a limit on how loud things can be.  Some pitches are more irritating than others, so if you can get some time from a sound level expert you can maybe select a meter that will measure "irritating" sound levels as opposed to "injurious".  Mostly you want to have a documented noise control program, which may be tough on the F2D planes but -- tough.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Steve Helmick

  • AMA Member and supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 9920
Re: What is the source of the noise?
« Reply #3 on: July 25, 2015, 04:18:30 PM »
The combat guys generally acknowledge that their (F2D) mufflers are more megaphones than mufflers, and make little, if any, reduction in dB's. It's driven by the rules. The rules mandated mufflers, but apparently didn't put any dB limits on them, unlike F2B, which has stringent dB limits. The folks in Ukraine and Russia (where the engines are made) don't care about anything but horsepower and meeting the requirements of the rules.

Note that the AMA stunt rules don't require a muffler, but almost everybody uses one of some type, and they all help. Some more than others. Wonder why that is? Yeah, me too.

If you're around electric stunters much, you'll notice they make a bit of a "bark" on hard corners, and it can be louder on either inside or outside corners, depending on whether running LH or RH prop rotation. There are various theories about what causes it. I tend to think it's blade flex or flutter, because I don't recall it happening when they were still running IC props on E powered planes. But then, I'm often wrong, according to my wife.  :o Steve
« Last Edit: July 25, 2015, 04:45:29 PM by Steve Helmick »
"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline EddyR

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 2562
Re: What is the source of the noise?
« Reply #4 on: July 25, 2015, 04:43:03 PM »
Frank    Who owns the field you are using? Is it a city park? Club field? Club run? As Steve said get a sound DB meter. They are not expensive. I have had one for years that I got from Radio Shack. Do not rely on a app in a phone or tablet. When I lived in Florida and the sheriff showed up with a noise complaint I asked him to take a reading on his meter. He didn't have one and I said my meter was saying I was under the county level for noise. He wanted to use my meter and I said no. That is your responsibility. One time I showed him the road background noise was louder than my model. What is the noise level,DB that is to loud in your area?
 A open exhaust is asking for complaints.  If you are in traffic and a kid with a booming sound system stops next to you it is aggravating but it is not very loud in DB level 200 ft from his car.
Ed 
Locust NC 40 miles from the Huntersville field

Offline Garf

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1817
    • Hangar Flying
Re: What is the source of the noise?
« Reply #5 on: July 25, 2015, 08:01:28 PM »
At one point in time, I was experimenting with aftermufflers on my ST G21 46's. I got it to where the prop noise was more than the exhaust note with little loss of power. Really strange.

Offline Keith Miller

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 210
Re: What is the source of the noise?
« Reply #6 on: July 25, 2015, 11:23:42 PM »
Both.

More so the combustion than the prop.
Ever had a shaft run? Pretty loud
Ever heard an electric? Pretty quiet.

My thoughts, others may vary.

Well, I've got an electric motor turning a 7x6 prop at 27.6k rpm, not much different than F2D; sound level is 104dB at 10ft.  There's no combustion noise in this case; all prop noise.  I race electric pylon, and they can be quite loud.

Offline Keith Renecle

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 887
Re: What is the source of the noise?
« Reply #7 on: July 26, 2015, 03:04:31 AM »
Hi Frank,
As others have said, high rpm makes a lot of noise, and changing the power source from IC to electric removes some of the noise that carries to the neighbours. The problem is not one of decibels however, it is the "noise nuisance" issue in the by-laws. Measuring the noise level of C/L models at the nearest neighbours house does not read much on a sound level meter, but you can sure hear them, and they unfortunately sound like a cat on a hot tin roof! Meowwwwwww......meowwwwww etc. as they go round and round. What is music to our ears, is hell to the neighbours, so it is a real problem. The noise from electric stunt planes does not carry far because of the low rpm, but an electric combat plane turning 20 000 rpm is loud.

The real source of info on this is Rob Metkemeijer who is the maker of the MB pylon engines. Rob did an investigation into F2C team racer noise a while ago. Not only is he one hellavu engine guy, but he is an acoustic engineer by profession. These F2C engines are all diesels and are a little quieter than an equivalent glow engine, but they are turning 30K rpm plus. Europe has very strict noise laws and the flying sites are being lost, but there is not much you can do to lower the noise that carries to the neighbours. I seem to remember that the FAI noise limit is 97 dB measured at 10 feet. The decibel is a log function and going down by just 3 dB is half the noise as measured on a dB meter, BUT.......to the human ear that 3dB is hardly noticeable and 94 dB is still very loud. Sooooo......the solution is..........move the neighbours!  VD~
Keith R

Offline Phil Krankowski

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1031
Re: What is the source of the noise?
« Reply #8 on: July 26, 2015, 01:02:14 PM »
Got a smartphone?  I am sure somebody you fly with does.  There are free and inexpensive sound meter software that run on phones.  There are limitations, and I am unsure how accurate these meters are, but they are close enough to get a good feel for relative loudness between different engines, propellers, etc. 

Phil

Offline Wynn Robins

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1684
Re: What is the source of the noise?
« Reply #9 on: July 26, 2015, 05:57:38 PM »
pretty simple answer - it the internal combustion - does you car/truck have a prop - nope - still makes a lot of noise
In the battle of airplane versus ground, the ground is yet to lose

Offline Gordon Van Tighem

  • 24 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 420
Re: What is the source of the noise?
« Reply #10 on: July 26, 2015, 06:41:00 PM »
Speculation and conjecture is not necessary. Back in the 80's when this was the hottest topic much research was done and several solutions developed. Muffler and engine manufacturers may still have the info, I am certain AMA, MAAC and FAI do.
As I recall, it isn't simple and sound from exhaust, propeller, venturi and airframe all needed to be addressed.
(The RC Pattern guys were in the lead for some time).
Speculation is fun, but research to solutions do exist.
Gord VT
MAAC 3738L, Life Member
AMA C3738L

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12804
Re: What is the source of the noise?
« Reply #11 on: July 26, 2015, 08:04:18 PM »
Speculation and conjecture is not necessary. Back in the 80's when this was the hottest topic much research was done and several solutions developed. Muffler and engine manufacturers may still have the info, I am certain AMA, MAAC and FAI do.
As I recall, it isn't simple and sound from exhaust, propeller, venturi and airframe all needed to be addressed.
(The RC Pattern guys were in the lead for some time).
Speculation is fun, but research to solutions do exist.

I remember reading a lot of good material on that.  Basically someone but a dB limit on RC aerobatic planes, and suddenly there was a reason to seek out high performance without high sound levels -- and it was found.

If you've got a magazine collection that goes back that far there may be some gold to be mined.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Carl Cisneros

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 889
Re: What is the source of the noise?
« Reply #12 on: July 26, 2015, 09:59:48 PM »
Back in the 90's when I was flying F3A, especially in the UK when we were stationed there, we used soft mounts for the motors
in our planes, (Sullivan had a nice one I used) and quieter props turning around 10k.
Props of choice then were APC and we also used quiet pipes. (OS Hanno pipe (red one), Hatori pipes and Bolly
Carbon fiber pipes)

I ran the OS Hanno Specials and they had gobs of power and they were nice and quiet in the air and on the ground.

Some of this can be adapted I am sure for our purposes, but maybe not all.
Carl R Cisneros, Dist IV
Control Line RB

Online Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 13717
Re: What is the source of the noise?
« Reply #13 on: July 26, 2015, 11:57:29 PM »
Speculation and conjecture is not necessary. Back in the 80's when this was the hottest topic much research was done and several solutions developed. Muffler and engine manufacturers may still have the info, I am certain AMA, MAAC and FAI do.
As I recall, it isn't simple and sound from exhaust, propeller, venturi and airframe all needed to be addressed.
(The RC Pattern guys were in the lead for some time).
Speculation is fun, but research to solutions do exist.

     It doesn't take much research if they are currently running open exhaust!  The use of an effective muffler will drastically reduce the noise and in many cases, improve the performance. Only when you get that, does anything even a little subtle come into play.

    Brett

Offline Gordon Van Tighem

  • 24 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 420
Re: What is the source of the noise?
« Reply #14 on: July 27, 2015, 04:50:52 AM »
So true, but like most things in life, when has common sense prevailed? I mention the work done historically because the answers took so long to become the 'common sense' of the day and so long to become common practise, (but more because I spent so many many hours in the tedious international debate at the time).
Brett, I appreciate your comment about 'improved performance' because it was a long time before modellers would accept that reality, in the day! I've been away for a few years, but our progress has been amazing, especially with pipes and electric.
G
Gord VT
MAAC 3738L, Life Member
AMA C3738L

Offline phil c

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2480
Re: What is the source of the noise?
« Reply #15 on: July 27, 2015, 01:57:36 PM »
From the experience of my former club, the Minneapolis Piston Poppers,  the noise level really doesn't matter.  If someone wants to complain they will and if they complain loud and often guess who wins.

At the time they had complaints from ONE lady who had moved into a nearby housing development.  She also complained about the noise from the county VoTech schoo whose property we were using(an unused ballfield right on a major highway.  The town and county has noise regulations, which the PP's were following, in addition to logging decibel readings for each flight.  The county engineer came out and wasn't able to measure any noise at the point closest to her property.  They couldn't hear the planes flying to take measurements.  She still complained.

One time I was there she came over and complained directly to the flyers, which she had been enjoined from doing.  I made a comment to her that the planes were all in accord with what the town had laid down.  She said: " I don't care how loud they are.  If I can hear it it's too loud!

There is no way to deal with that kind of attitude.

phil Cartier

Offline Norm Furutani

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 212
Re: What is the source of the noise?
« Reply #16 on: July 27, 2015, 02:03:37 PM »
Years ago, we started flying R/C gliders on a new field. The police arrived and explained that they had received a noise complaint. We showed the police we were using a hi-start and none of the planes were engine powered! They shook their heads and left. We assumed that neighbors saw us having fun and just wanted us to go away.

BUT... as a music teacher, I did a lesson on noise vs. music. Noise is relative, example: one of the most annoying noises is the sound of a mosquito in your bedroom on a hot summer night, but for the mosquito of the opposite sex, this could be wonderful music!

For some model airplane music, check this out! https://www.flickr.com/photos/44670670@N02/5450373210/?fb_action_ids=10202051642052443&fb_action_types=flickr_photos%3Ashare&fb_ref=w


F1C's at 30K, Isaacson Winter Classic, Lost Hills, CA

Norm

Offline dave siegler

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1128
  • sport flier
    • Circlemasters Flying club
Re: What is the source of the noise?
« Reply #17 on: July 28, 2015, 05:07:48 AM »
I remember reading about the patten guys and noise reduction.  They did a lot of work on it. 

If I remember the contributions to noise were. 

Good Mufflers first big canister type were suggested.   
limits on engine RPM second.   Above about 20krpm, about 1/2 noise is prop.  Do the math, a 7 inch prop at 27k, has a pretty high mach number.
Soft mounts to eliminate airframe noise
carburetor inlet muffling. 
Dave Siegler
NE9N extra class
AMA 720731
EAA 1231299 UAS Certificate Number FA39HY9ML7  Member of the Milwaukee Circlemasters. A Gold Leader Club for over 25 years!  http://www.circlemasters.com/

Offline Steve Scott

  • 21 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 673
  • Terrorizing earthworms since '65
Re: What is the source of the noise?
« Reply #18 on: July 28, 2015, 05:32:24 PM »
I've been flying a high performance electric RC foam wing with an APC 7-4 electric prop and it is LOUD (and fast).  Quique Somenzini, who used to work for Horizon Hobbies, said most of the noise comes from the proximity of the prop to the trailing edge of the wing - these wings all have rear-mounted engines.

« Last Edit: July 28, 2015, 06:00:05 PM by Steve Scott »

Offline john e. holliday

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 22752
Re: What is the source of the noise?
« Reply #19 on: July 28, 2015, 08:13:14 PM »
That sounds like one of my scale race planes with a Nelson.
John E. "DOC" Holliday
10421 West 56th Terrace
Shawnee, KANSAS  66203
AMA 23530  Have fun as I have and I am still breaking a record.


Advertise Here
Tags:
 


Advertise Here