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Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby ghedger42 » Sun May 12, 2019 11:33 pm

The Boeing 707 model is AMAZING: every detail, even the engineer panel functions, with pump gauges. This is an awesome sim model.

One weakness, as is the case more often than not, is the engine audio was an afterthought, and the engine sounds are the glory of aircraft from this era. So, I modeled the JT3C based on harmonic deconstruction and reconstruction and am happy to offer this as an update, such that it now sounds like an aircraft with JT3C engines both inside and outside the aircraft. Also, the wind sounds have been improved.

I'm modeling the APU as well, but as this appears to be a very early 707 I'm not sure if the APU startup sounds would be appropriate given it seems like this one intends to use a huffer cart (not automatic like later 707s and the DC-8).


When I'm ready, who would be the appropriate person to put this into the release -- assuming, that is, that the work is acceptable to the community?
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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby Johan G » Mon May 13, 2019 11:12 am

ghedger42 wrote in Sun May 12, 2019 11:33 pm:When I'm ready, who would be the appropriate person to put this into the release [...]

If the aircraft is from the official hangar the maintainer is D-MKF1 / Marc Kraus of the Lake of Constance Hangar.

You could contact him through email (you will find it in the -set.xml file), but if you are familiar with Git and Git repositories I think he might appreciate if you cloned his development repository added your changes to your clone and did a pull request.

ghedger42 wrote in Sun May 12, 2019 11:33 pm:[...] assuming, that is, that the work is acceptable to the community?

As long as you are the author of the changes/additions (or the sources are known and are compatible with the GNU GPLv2 license). FGAddon, the official FlightGear hangar uses "GNU GPLv2 or later" terms.


ghedger42 wrote in Sun May 12, 2019 11:33 pm:[...] I modeled the JT3C based on harmonic deconstruction and reconstruction [...]

Could you elaborate on what that you mean with that? Is it building up the sound from filtered white noise, or perhaps with separate noise for N1 or N2? Seems interesting in any case.
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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby legoboyvdlp » Mon May 13, 2019 11:43 am

ghedger42 wrote in Sun May 12, 2019 11:33 pm: I'm modeling the APU as well, but as this appears to be a very early 707 I'm not sure if the APU startup sounds would be appropriate given it seems like this one intends to use a huffer cart (not automatic like later 707s and the DC-8).


Our 707 has both - the APU controls are bottom right of the engineer panel.
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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby ghedger42 » Mon May 13, 2019 6:46 pm

Thanks, both of you. I'll get in touch with Marc Kraus on this.

BTW this one is REALLY good, better than mine, and the files are free for use as long as they aren't used as part of any payware.



It's for Microsoft FSX, though, and 61MB (!!!) in size....
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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby AndersG » Mon May 13, 2019 7:00 pm

ghedger42 wrote in Mon May 13, 2019 6:46 pm:BTW this one is REALLY good, better than mine, and the files are free for use as long as they aren't used as part of any payware.


That would seem to not be GPL v2 or later compatible, however, as GPL v2 or later software may be sold, but, of course, allow further distribution by the recipient.
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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby ghedger42 » Mon May 13, 2019 7:02 pm

legoboyvdlp wrote in Mon May 13, 2019 11:43 am:
Our 707 has both - the APU controls are bottom right of the engineer panel.


Are you one of the authors/maintainers? I just see the one 707 in the list. Will play with that for the APU.

Can you confirm that the base 707 your selected is indeed the early J57/JT3C one (10,000 lbs thrust)?
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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby ghedger42 » Mon May 13, 2019 7:04 pm

AndersG wrote in Mon May 13, 2019 7:00 pm:
ghedger42 wrote in Mon May 13, 2019 6:46 pm:BTW this one is REALLY good, better than mine, and the files are free for use as long as they aren't used as part of any payware.


That would seem to not be GPL v2 or later compatible, however, as GPL v2 or later software may be sold, but, of course, allow further distribution by the recipient.


Probably not. I don't plan to use anything from it anyways for philosophical reasons: it relies too heavily on samples whereas I'm trying to model the actual harmonics, which makes for much smaller loops that are clean-room engineered from scratch (based on harmonic analysis and Fourier recombination).
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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707  

Postby legoboyvdlp » Mon May 13, 2019 7:09 pm

I am not a maintainer - I am referring to the 707 in fgaddon (our official SVN repository for aircraft on sourceforge), also available through the launcher or flightgear.org. As for engines as far as I know our engines are the 17500 lb Rolls Royce Mk508 engines.
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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby ghedger42 » Mon May 13, 2019 8:12 pm

There's much I don't know about the evolution of startups and APUs. What I've been modeling are actually JT3D engines (based on the DC-8-61). I don't know why the -61 and -62 sound differently prior to rotation -- the 61 has a loud, almost primordial sounding howl, presumably the bleed valve opening to spin the engine prior to combustion. The -62 lacks this sound. Finding samples of these engines is tough, with the ideal being the sampling and harmonic analysis of a single engine. Maybe I'm overthinking it.
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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby Octal450 » Mon May 13, 2019 8:15 pm

Hello and welcome
I do not believe any real 707s had APUs. It was retrofitted on some maybe, but from the factory none did.

Keep in mind, that the recording could also be missing part of the sound for various reasons.

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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby bugman » Tue May 14, 2019 8:04 am

Also note that the engine sound outside, inside the cockpit, and inside the cabin are all very different!

For the copyright issue, the copyright owner of the original sound would probably have a legal claim against you. You did derive your sounds from their property, independently of what the end creation is or even sounds like. Remember that we have to abide by the copyright laws of the entire planet to be legally safe (so US or European fair use augments do not work here). So the safest would be to use only GPLv2+ or public domain sources. In most cases you can ask the original content creator if they'll licence just the sound to you as GPLv2+ (this is the GNU General Public Licence version 2 or later, with zero additional restrictions)., or if they'll let you use it as public domain. You'll need a public statement though that we can legally rely on. For example you can ask in the YouTube comments section, if that is the source. If you detail what you'd like to do with the sound track, and that it will be open source and you'll be making zero profit, then most people will be reasonable and grant you permission.

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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby ghedger42 » Sat May 18, 2019 6:28 am

bugman wrote in Tue May 14, 2019 8:04 am:Also note that the engine sound outside, inside the cockpit, and inside the cabin are all very different!

For the copyright issue, the copyright owner of the original sound would probably have a legal claim against you. You did derive your sounds from their property, independently of what the end creation is or even sounds like. Remember that we have to abide by the copyright laws of the entire planet to be legally safe (so US or European fair use augments do not work here). So the safest would be to use only GPLv2+ or public domain sources. In most cases you can ask the original content creator if they'll licence just the sound to you as GPLv2+ (this is the GNU General Public Licence version 2 or later, with zero additional restrictions)., or if they'll let you use it as public domain. You'll need a public statement though that we can legally rely on. For example you can ask in the YouTube comments section, if that is the source. If you detail what you'd like to do with the sound track, and that it will be open source and you'll be making zero profit, then most people will be reasonable and grant you permission.

Regards,
Edward


I'm quite aware of high-frequency drop-off, having done a fair amount of professional audio in the past (including payware); only someone naive would use the same audio for inside and outside.

All my sounds are my own work, and there's no possible way to prove which JT3D engine of the thousands manufactured a particular harmonic analysis came from (hint: it isn't from the video posted earlier in the thread -- for all you know, it may be something I or a friend recorded): the whole point of decomposition and reconstruction is to eliminate extraneous noise and end up with a much purer sound than just samples., which are, frankly, cheesy, at least in my opinion, since very few in my experience take time to ensure that the loops begin and end at the convergence of all the constituent harmonics at exactly the same phase. Fourier analysis is about sine waves -- analog world, not digital, and not recorded and pasted together audio directly from something recorded into a microphone...

I was trying to offer something to improve the FlightGear experience as a favor to the community, for free (GPL2), but it seems like this may be more hassle than it's worth, so perhaps it's best if I simply not release the work at all. People can have the 737 sounds for the 707 and think that's what 707s sounded like...

Thank you for your input.
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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby Johan G » Sun May 19, 2019 1:07 pm

I think most of us made the assumption that your sounds was recorded samples, and that our worries about getting non GPL compatible content into our stuff was making us a bit twitchy.

Perhaps explaining roughly how you do your sounds would help.
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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby Maerchenprinz » Wed May 22, 2019 10:53 pm

Yes, it seems as if most people either haven't read all posts or simply don't understand what it's all about:
ghedger42 uses a technique which makes any discussion about licensing totally obsolete!
And after the stage of harmonic analysis, it's easy (well, at least for some people!) to construct any inside, outside, passenger with earplugs, pilot with headphones... derivative of it.
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Re: Improved Engine Sound work done: P&W JT3D on Boeing 707

Postby erik » Fri May 24, 2019 10:54 am

I agree, harmonic reconstruction of audio samples is like recreating the Mona Lisa with Lego blocks. It seems to resemble the original but they can't compare. So don't let anyone hold you back with this, it's a worthwhile technique in this case.

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