Engine samples - some info

[HornetMaX]

Hi all,
some info I was about to PM to some users and may be of interest to others here.

The noise of an engine has typically a "main frequency" (in Hz) equal to (Ncyl * RPM / 120).
That's for a 4-stroke engine, for a 2-stroke it's /60 instead of /120.

This frequency corresponds to the frequency of the detonations in the engine.

If you have a sample of an engine, throttle open at a fairly constant RPM, to get the main frequency (and hence the RPMs at which the sample has been taken), you need to plot the spectrum of the signal and find it's peak value. For example, you can use Audacity (free), Analyse/Plot Spectrum.

There are tons of technical parameters that require some knowledge in signal processing (don't ask, I will not try to explain, way too long).
Also, it gets a bit more complicate for sample with throttle OFF, as ... there are no detonations

MaX.

[Hawk]

Hi Max.

I'm creating a Yamaha YZR 500cc GP Bike from scratch. I have obtained good quality on-board video of Kenny Roberts riding this machine, the sound is very good; is it possible to use the engine sound from this video as a sample for the YZR?
The engine sounds cover the whole range of RPM but not constant at specific RPM ranges, just the engine RPM you'd expect from a rider starting the engine in pits, slowly riding out of pits and then racing the bike around a track. It would be great to be able to use the original engine sound for the bike - Would it be possible to sample and use this engine sound? It is so clear and crisp, I hope it is possible to use as a sample.

[Warlock]

I'm sorry to say but with not 5 secs of constant rpm.... i doubt. 

[HornetMaX]

I think it will require a bit of work and I'm totally not sure about the outcome.

If the RPMs are not really constant over the desired time, it is possible to "stretch" the interval to make them almost constant.

However notice I'm a noob at sound editing: I tried to produce some loopable samples this afternoon and I can't say it was a great success (as Borat would say).

MaX.

[Hawk]

I presume these sound editing suits are capable of taking a moment in time of sound and then surely you could just copy that moment in time of sound and create enough sound for that particular piece of sample you need, and then keep adding and mixing samples together until you had enough of a time sound sample as needed to work with and manipulate into the finished sample/s I'd need?

I've no experience using sound sampling/editing suits, so I don't really know anything of their capabilities. But I'd be surprised that if one knew what one was doing with a good editing suit that the above could not be achieved?

I wish I had the time to learn and give it a try....


Edit: Is creating loopable sound samples similar to a texture artist having to create textures on a model without any obvious texture joint seams?

[Warlock]

I presume these sound editing suits are capable of taking a moment in time of sound and then surely you could just copy that moment in time of sound and create enough sound for that particular piece of sample you need,

Yes u can cut just a little bit of the sound  , lets say 20 revolutions of the engine,and loop it but it will sound awfull, trust me, i've been there 

[HornetMaX]

Edit: Is creating loopable sound samples similar to a texture artist having to create textures on a model without any obvious texture joint seams?

Yes, exactly.

And I confirm: taking a small sample and looping it is usually very bad.

MaX.

[Stout Johnson]

Thnx MaX for sharing your info on how to calculate the rpm of an on engine sound sample. It sounds logic so it should work I guess I also noticed that when you work with engine sounds of one particular engine over a period of time, after a while you can tell the rpm (to a certain point of accuracy) just by listening...

Thank you also for this information http://forum.piboso.com/index.php?topic=636.0, I will look into this as soon as I have some free-time again. I feel that with my sound samples, if I can get the mixing and the blending done perfectly, I will be able to produce very decent to great sounds.

Generally I like this topic and I think if we could combine all our knowledge together we could at least decent sounds. In the long run I hope there will be some kind of tool available. In terms of engine.scl creating I am working on a spreadsheet that automatically generates the engine.scl if the user can give reference rpms of the sound samples... I will share that as soon as I am finished with that. In terms of checking sounds in-game and how they blend into each other it would be quite handy if we would have some sort of tool, that would allow to sort of "run the engine out of the game" (revving, applying throttle gradually, shifting thru gears etc.) - sort of like a dyno run. That way you could easily check how your changes effect the sound in-game. Maybe it would also allow tweaking the pitch and the fade in/out and therefore the engine.scl from that tool. That would help A LOT and save time.

[Stout Johnson]

However notice I'm a noob at sound editing: I tried to produce some loopable samples this afternoon and I can't say it was a great success (as Borat would say).

As for sound samples: this is a great source for motorcycle sounds http://www.sounddogs.com/results.asp?Type=1,&CategoryID=1041&SubcategoryID=22. These samples are not free, however there is a way of capturing sound that your sound card plays directly - therefore there is a way to use them if you look thru the samples available, there is always a decription of the sample - look for samples that write 'constant' or similar things (http://www.sounddogs.com/extendedsearch.asp?keyword=motorcycle%20constant&ddCategory=0). Then listen to samples that have decent, relatively constant sounds, and you can use them.

As for making sample loopable:
-Overall, if the sample is pretty much constant you can use smaller samples, if it is not very constant it is adviced to take rather longer samples. However there is a limit, if it is not very constant it will sound awfull in-game...

-in audacity you can change the view of the sample to pitch view (its that drop-down next to the name of the sample), which helps determine where the sample sounds relatively constant

-I personally, find it handy to cut the sample at similar stages of the sound (if you zoom in on audacity you can see the waves, try to cut it where it makes sense) - this in itself can create nicely loopable sound (but only if it is very constant)

-if it is not very constant and sounds awfull as a loop (you can always check in audacity with (shift+space), I will copy and paste my sound (strg+D) and then go to 'effects' and then it should say ('backward' or 'reverse' - dunno, I dont have time to change to english version of audacity now ) - this way you can create a copy of your sample, but reversed. if you add that to your file and have the normal sample played first, then the reversed sample right after you can create loopable samples... listen to it in loop (shift+space) - if it sounds decent - save it in mono and try it - if not go back to square one and try it again with a different sound sample

[C21]

Really Great and decent Info Stout !
Much appriciated.

What will be the better Sample:
A) Bike stand still. Revved up in idle to a steady rpm value (e.g. 3000rpm) and then Recording.
B) Bike on a dyno, Rolling, 3rd gear, Holding at 3000, Recording.

Do we Need One Sample in idle and One Sample of the Revved Engine or more?
Sorry to ask...don't have a Look into it yet.

[HornetMaX]

What will be the better Sample:
A) Bike stand still. Revved up in idle to a steady rpm value (e.g. 3000rpm) and then Recording.
B) Bike on a dyno, Rolling, 3rd gear, Holding at 3000, Recording.

Do we Need One Sample in idle and One Sample of the Revved Engine or more?

Dyno is much better cause the engine is under load (that's what you need for ON samples).
If the dyno can keep the wheel spinning at constant speed, then you can also capture OFF samples (throttle shut) easily. Otherwise OFF samples are more complicate to grab.

Generally you need 1 sample in idle, + a few samples throttle ON (constant RPMs) and a few samples throttle OFF (constant RPMs).
How many ? I'm not sure it matters a lot, probably even 3 ON + 3 OFF are enough but as you may not have the bike on the dyno every day, just take as much samples as you can (e.g. every 2000 RPMs).

You may avoid taking a sample at the limiter, as GPB seems to do that automatically.

Each sample should be 3-10 seconds long (the longer the better).
Maybe you want to do the high revs samples (ON and OFF) a bit longer, as these will cover most of the range and in-game you may stay throttle wide open for long periods of time (so a longer sample will loop less).

Be sure to avoid saturation (have to check the recording level).

And ... good luck

MaX.