Ummm about his new engine sound thingy

[straffo]

Originally posted by GScholz
I know what FTP is but SFTP?

Secure FTP (somthing like SSH File Transfer Protocol) using tuneling and encryption if I'm not complelty wrong

[ergRTC]

YEs it is secure ftp.  When I get to the lab tomorrow I will set up a way for you to send me the file.

Widewing

1) I think the p51 wep is a bug, as I assume most people believe at this point.

2)Of course you are right about the boost and the over boost, I am only arguing against the silly idea most people have that increased throttle = increased rpms, and that increased throttle means altered pitch (of course under certain circumstances they do, pushing up from idle on the runway and the like).

As you know neither of these are correct IF ...  all of the things that would keep you from blowing up your engine are accomplished by the game.

If your hub is altering your pitch to maintain constant rpm,  as long as your giving it enough throttle the keep the prop turning, your rpm should remain constant.  

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Now, as for the unreal side of this, I am sure they are refining things like how the pressure responds to dropping rpm at constant throttle.   HTC have said they dont want this to be overly complicated, so I assume engine blowouts due to mismanagement are not going to happen, although I wish they would....

as far as pilots, hitech owns a plane does he not?  


erg

[WhiteHawk]

does anybody know how much more fuel mix is sucked into an cylinder with higher throttle settings?  I cant imagine its THAT much more at high throttle than idle.  I assume it has to be more, but i cant think mechanically of why?  The suction is increased, but so is the frequency of the stroke.  Most of the added fuel goes into firing more cylinders per unit of time.
  I think a lwan mower should be a good example of the noise model here.  its definatley more pitch oreinted than volume, imho.

[Widewing]

Originally posted by WhiteHawk
does anybody know how much more fuel mix is sucked into an cylinder with higher throttle settings?  I cant imagine its THAT much more at high throttle than idle.  I assume it has to be more, but i cant think mechanically of why?  The suction is increased, but so is the frequency of the stroke.  Most of the added fuel goes into firing more cylinders per unit of time.
  I think a lwan mower should be a good example of the noise model here.  its definatley more pitch oreinted than volume, imho.

Typical for the Allison V-1710-89 as installed in the P-38L:

Power setting of 1,600 RPM @ 22 in/Hg consumes 46 gallons per hour.

Power setting of 3,000 RPM @ 54 in/Hg consumes 334 gallons per hour.

Not an insubstantial difference.... Little more than doubling the RPM and MAP results more than 7 times the fuel burn rate.

I think its a great idea for HTC to accurately model fuel burn rate and engine management.

Now, stand within 10 feet of a Packard Merlin at idle. It's loud but not painful. Do an engine run-up to 30 in/Hg and it gets painful. Go to full power (tail tied down, as well as chocked and tied down main mounts) and you better have hearing protection. It has nothing to do with the pitch of the sound, it's the huge increase in decibel level that causes the pain.

My regards,

Widewing

[Widewing]

Originally posted by ergRTC
as far as pilots, hitech owns a plane does he not?  

Yes, HiTech does own a sport plane, an RV8-A with tricycle gear if I'm not mistaking.

It is powered by a Lycoming with a Hartzel constant speed, two blade prop. It's a kit plane, and not one for someone with minimal mechanical skills either. They are highly regarded in the sport plane community. You can check out the various RV kits at Van's Aircraft

My regards,

Widewing

[gatt]

Originally posted by Waffle BAS
Still a lawn mower doesn't have as much of a decible decrease with power as the throttle does with patch 13.

Currently as is - the throttle sounds like a volume control....not controling RPMs

Same thing here ...

[Waffle]

Originally posted by Widewing
Typical for the Allison V-1710-89 as installed in the P-38L:



Now, stand within 10 feet of a Packard Merlin at idle. It's loud but not painful. Do an engine run-up to 30 in/Hg and it gets painful. Go to full power (tail tied down, as well as chocked and tied down main mounts) and you better have hearing protection. It has nothing to do with the pitch of the sound, it's the huge increase in decibel level that causes the pain.

My regards,

Widewing

Now this P38 has to be tied down, correct, so that means there's prop on it......how much of the decible increase is in prop noise??

I'm just tring to sus out the "engine" only noise..so lets take the engine out off the 38 and fire it.... no prop....

measure the dbs then....measure the pitch(audible) change in the engine only..as the throttle is increased. There will have to be a pitch change.....Increasing the throttle in in any engine will affect the pitch.




I hear planes land / take off now and then from the airport near here...only recently did I start listening.....

Now this is from the ground, so am I hearing prop noise or engine? - the plane was finishing taking off - and had a resonance off around 400hz...my guestimation.  It cut power and leveled off.....the pitch(audible) dropped to near 300-320 HZ.
 400hZ is a little lower than a standard A note on a guitar. "G" is about 315, i believe. It did not get softer, but stayed the same level Db wise....

So now this is PITCH (audio) change.. was it a prop, or the engine?

[Waffle]

Thats It!

I'm going to the airport with a db meter, Real time frequency analyzer  /  oscilliscope and a 12 Pack!

[AKWeav]

It's funny, but I thought AH1 had it right. The volume of the engine didn't decrease so much, but reduce the prop rpm and the rpm of the engine decreased.

Current AH2 engine sounds are much like ww20l (a feature I didn't care much for), reducing throttle setting had no effect on engine rpm sounds. Yet switching from max rpm to economy rpm produced a reduction in engine rpm sound.

Don't think I care much for the present settings.

[ergRTC]

"Currently as is - the throttle sounds like a volume control....not controling RPMs"

I wish somebody with more of a clue than me could help clear up the throttle and rpm thing.  In these planes throttle (while flying) does not = rpm.  So saying something about high throttle and idle, or something about volume control not rpms leads to a unreal expectation of the behavior/sound.

Also, fuel consumption can be related to throttle position not just rpms, as in the example widewing gave us.  Engines under load maintaining the same rpm as an engine not under load consumes much more gas.  Example granny gear in a truck pulling something or an idling truck just sitting on the pavement.

[Widewing]

Originally posted by Waffle BAS
Now this P38 has to be tied down, correct, so that means there's prop on it......how much of the decible increase is in prop noise??

I'm just tring to sus out the "engine" only noise..so lets take the engine out off the 38 and fire it.... no prop....

measure the dbs then....measure the pitch(audible) change in the engine only..as the throttle is increased. There will have to be a pitch change.....Increasing the throttle in in any engine will affect the pitch.




I hear planes land / take off now and then from the airport near here...only recently did I start listening.....

Now this is from the ground, so am I hearing prop noise or engine? - the plane was finishing taking off - and had a resonance off around 400hz...my guestimation.  It cut power and leveled off.....the pitch(audible) dropped to near 300-320 HZ.
 400hZ is a little lower than a standard A note on a guitar. "G" is about 315, i believe. It did not get softer, but stayed the same level Db wise....

So now this is PITCH (audio) change.. was it a prop, or the engine?

Let's keep this as simple as possible.

Decibels is a measurement of pressure.
Pitch is a measurement of frequency.

Regardless of the frequency, without an increase in pressure, there is no increase in "loudness".

As to the P-38, it's a poor plane to use for this type of analogy. Its exhaust is effectively muffled by the turbo installation. P-38s are surprisingly quiet. Likewise, the P-47 is less obstrusive than the F6F, despite having, essentially, the same powerplant.

On the other hand, the P-51D has short stacks that are in line with the open cockpit when on the ground. Exhaust noise is direct and very loud. Prop noise is substantially less than engine noise when on the ground. At high altitude, prop noise can be incredible when the prop tips go supersonic (remember that props have a spiral motion through the air, and tips going supersonic was/is common for a large diameter prop turning at max rpm, especially up high where the relative speed of sound is considerably lower than at sea level).

By the way, you wouldn't tie down the tail of a P-38 for a high power run-up, it has a nose wheel. You may want to tie down the main mounts because it's probable that the brakes wouldn't hold and it might jump the chocks.

My regards,

Widewing

[Waffle]

Correct decibles are a measurement of sound pressure levels...

Pitch has, in this thread, been misconstrued as prop pitch and frequency (audio). As i blieve RPM has been to horsepower


"Let's keep this as simple as possible.

Decibels is a measurement of pressure.
Pitch is a measurement of frequency.

Regardless of the frequency, without an increase in pressure, there is no increase in "loudness"."

What I am getting at is that the "Engine" only sound seems so very off in a SPL (decible) way right now.

Take the engine starting right now. It's fine until the sound jumps over to the "stock" engine .wav file.

If your throttle is off - It sounds like you engine drops out when the start cycle completes.

The very last 3/4 seconds of the engine start sound, sounds to me, what an engine at idle would sound like.

So in a perfect world, we'd have a idle engine with a nice low lope to it (or other engine characteristics depending on the engine).

Then as we increase the throttle to the engine, the frequency WOULD rise To the approrite sound of "X" engine at "Y" RPMS.

You cant fight physics... Audio frequency will always increase/decrease in proportion to how many RPMs the engine is putting out, as will exhaust noticiably change. A percieved loudness is due to the coupling / phase of exhaust...hence "tuned" pipes in autos and what not. There will also be a slight increse in Db as more power is applied due to the strength of the combustion and rate of combustion.

There are also many variable and different types of engines...
some resonate at different rpms differently...some RPM setting things will seem to  "settle" out....when a harmonization occurs between Engine exhuast / RPMs / vibrations...

Think of when you're driving on a highway and there's a certain speed your car just "likes" It's seem quiter and smoother.

Like I said before - Engine only...let not take prop noise into account yet....


Thats another subject that should fall into place once the engine sound is hashed out.


hehe Widwing...glad you realized about the not tying the 38s tail down...got that from your first post....lol. hindsights always 20/20 i guess Actually - I miscontrued your previous post....lol you were talking about a merlin..I had allison on the head

[AKWeav]

Hmm, let me see if I can explain in written words what it is about this change in engine sound that bothers me.

It's like listening to a recording of an engine constantly running at high/mid rpm range. Then to simulate the engine returning to idle, the volume is simply reduced. No change in sound pitch, or the combustion detonation frequency.

It needs more work HiTech.

[Tilt]

The faster the engine the higher the sound frequency.
The slower the engine the lower the sound frequency.

The bigger the "bang" in the cylinders the louder (bigger sound waves) the engine. (more fuel /higher manifold pressure)
The smaller the "bang" in the cylinders the quieter (smaller sound weaves) the engine. (less fuel lower manifold pressure)

Prop noise is speed and angle of attack to generate noise from air turbulance.

However air "slap" would be louder at higher AoA. Which would be permitted at higher manifold pressures.

As the prop rpm increases the frequency would increase.


Fundamentally the frequency increases with rpm but the volume should increase with manifold pressure................... which is a function of both throttle and rpm. (and additive)

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Waffle I believe AH has always assumed that pitch control is automated as a function of RPM setting. Hence at a given rpm setting the prop pitch changes with every change inmanifold pressure to utiles the power available without changing rpm.

RPM can only be changed by the pilot once set the prop pitch changes to maintain it.

[GScholz]

Tilt got the fundamentals down nicely. However I'd like to add that the mechanical noise of the engine is not reduced by reducing boost. The supercharger is linked to rpm and will whine just as much at low boost as at high boost, same with valve ticking, engine vibration and any other mechanical sound. The best way to recreate this would be to have two different sounds. One for the mechanical sounds that stay constant at a constant volume level regardless of boost, and one sound with the deep roar of the engine which gets lower with the reduction of boost. Both sounds change in frequency with rpm. A second way would be to only change the volume of the deeper tones (mid-bass tones) of the sound, while leaving the higher tones (typical of mechanical noise) at the same volume. A third/second sound of engine "sputtering" may be mixed in for low rpm and low boost levels.

My friend who runs the http://www.lordpanzer.com site has graciously agreed to host the 109G2 Cockpit recording for me.

In-Cockpit_flight_109G2.mp3 (12 megs. Right-click - "Save as")