Airplanes have noises associated with them of course, and X-Plane (XP) allows the airplane designer to customize the sounds associated with his or her plane. The following will attempt to explain how this is done within XP.
Current Stable XP release - 8.50 (as of this date 8.60 beta 8 is out)
It is my hope that perhaps the community will take more advantage of this type of resource; I believe that we as XP airplane designers are constantly reinventing the wheel and this might save us all a bit of time and trouble.
Default sounds
Within your main XP folder is another folder named "Resources". Inside are folders such as Earth Nav Data, Default Scenery, Plugins, Preferences, and "Sounds". Inside this Sounds folder (hereafter referred to as Resources/Sounds) are six subfolders.
Each of these subfolders contains a collection of .wav files (.wav describes a fairly common type of audio file usable by both Macs and PCs). The titles of the folders are somewhat self explanatory:
- "Alert" contains messages such as a voice saying "200 feet". If your aircraft has instrumentation that warns the pilot as the plane descends through 200 feet, XP will play this message.
- "Contact" contains sounds associated with the airplane interacting with ground. Crash sounds, rolling on the runway, tire screetch upon touchdown, etc.
- "Engine" contains generic sounds for piston engines, turboshafts, jet engines etc.
- "Systems" contains sounds for flaps, gear, avionics, APU, etc.
- "Weather" contains sounds for rain hitting the windshield, hail, wind, etc.
- "Radio Chatter" contains tower to plane communications and so on. Radio chatter can be turned on or off in XP; in the game, under "Settings" choose "Sounds..." and turn radio chatter on or off.
You can listen to these .wav files by just double clicking on them. On a Mac usually a Quicktime panel will pop up, it could be iTunes depending on how your preferences are set up. On a PC usually a WindowsMediaPlayer panel will open and you can listen with that.
If your airplane has no custom sound information these are the sounds that XP will use when your plane is loaded. They're not bad, but they are limited and custom sounds go a long way to enhancing your airplane's "realism" in the sim.
Copyright Issues
A note on copyrights. I am not an expert or even knowledgeable in this area, so please assign the proper value to these comments. As we all do these days, the first place you will look for sounds is the internet, and there are lots of sounds out there. Some authors place restrictions on their copyrighted work (as is their right) and some don't. Some just ask for attribution, i.e. if you use their stuff you have to give them credit in a written description of your aircraft. Most do not want their work to be used in for profit activities. X-Plane.org is (rightfully) very strict on this issue. As an aircraft designer, you should err on the side of caution; include a text file description of your aircraft in the aircraft file and credit everyone appropriately. If the work is copyrighted and has restrictions, just look elsewhere for appropriate sounds. Its a small thing and its easy to cheat; do the right thing.
Customizing the sounds for your airplane
Now, on to customizing the sounds for your airplane,
When you design an airplane in XP or download one that someone else has posted, inside the top level aircraft folder are folders such as "Airfoils" or "Objects" or "Weapons". There might also be a folder called "Sounds", inside of which can be subfolders with .wav files exactly the same as the Resources/Sounds folder discussed above. If this sound folder exists in your aircraft folder XP will use the contents instead of the default sounds in the Resources/Sounds folder.
So, if you want to use custom sounds for an aircraft, create the folder called "sounds" inside your main airfraft folder and within "sounds" create the subfolders "alert" "contact" "engine" "systems" "weather" and "radio chatter". You don't have to create all of these; you could create only the subfolder "engine" for instance. XP would use default sounds for everything except for the .wav files you have placed into your "engine" sub folder.
You have to name the .wav files you use with your airplane using the following convention:
Suppose your twin engined plane is called "mytwin" and you want to put in custom engine sounds:
- create inside the aircraft folder a (sub)folder called "sounds"
- create inside this sounds folder another (sub)folder called "engine"
- place two copies of your custom engine sound .wav into mytwin/sounds/engine; name one of them "mytwin engn1.wav" and the other one "mytwin engn2.wav".
This convention holds for all of the .wav files you use as custom sounds: airplane name<space>XXXXX.wav
On an fairly advanced airplane you might typically find all of the subfolders except for "radio chatter". As this is being written, .org member "wendygirl" has posted radio chatter files based in Japan as opposed to major U.S. cities; substituting these .wav files for the originals will make XP flying in Japan's airspace a bit more realistic. Wendygirl's files are intended for XP users who might want to replace the default Resources/Sounds radio chatter: the point here is that whatever you put into the custom sound subfolders will be used by XP; if in your custom sounds "Alert" folder you replace the "200 ft" message with a recording of you saying "oopsie daisy" this is what XP will play when your plane descends through 200 feet.
- Specification of the .wav files:
- "sampling rate" of the .wav files should be: 22.050 kHz
- "length" in seconds of the .wav files should be: ???
- "other attribute" of the .wav files should be: ??? ???
List of Sounds
- In the "Alert" folder:
10ft.wav 20ft.wav 30ft.wav 40ft.wav 50ft.wav 100ft.wav
200ft.wav 300ft.wav 400ft.wav 500ft.wav 1000ft.wav
caut.wav glid.wav gwrn.wav mini.wav pull.wav
sink.wav wshr.wav tcas.wav stall.wav alternator_off.wav
radar_lock.wav transonic.wav
- In the "contact" folder:
land.wav lrun.wav ROLL_RUNWAY.WAV BOOM1.wav
skid_dry.wav loff.wav boom2.wav boom3.wav boom4.wav
land_water.wav roll_ground.wav skid_wet.wav
note - I don't believe these are case sensitive in any way, can anyone confirm this ?
- In the "engine" folder:
engn1.wav engn2.wav engn3.wav engn4.wav
and so on, you can have as many of these as you have engines....
prop1.wav prop2.wav prop3.wav prop4.wav
and so on, you can have as many of these as you have props; if you have multiple props on one shaft....maybe someone will have an answer for that one !
star1.wav star2.wav star3.wav star4.wav
and so on, you can have as many of these as you have starters...
reverse_thrust.wav afterburner.wav
There are several generic engines sounds in the "sounds" file located in "resources" that I will not duplicate here. The reader can look, or rather, listen to these and determine if they are appropriate to his design.
- in the "systems" folder:
flap.wav gear.wav mdot.wav mdas.wav stall.wav
Gear_Warn.wav alt_alert.wav APU.wav avionics.wav
click.wav climb.wav dash_MIDDLE.wav dash_OUTER.wav
descend.wav dot_INNER.wav dot_MIDDLE.wav seatbelt.wav
I have seen two planes with a "stal.wav", I believe this is a typo ?
- in the "weather" folder:
rain.wav wind.wav hail_impact.wav hail.wav thunder1.wav
thunder2.wav thunder3.wav thunder4.wav thunder5.wav
thunder6.wav
I will update these periodically as we "discover" more of these...
A lot of the sounds in the "resources/sounds" folder should probably never be duplicated in the sound folders of individual aircraft. For instance the "thunder" series of .wav sounds; why include these with an individual plane ?
Editing .wav files
- .wav files can be edited; to do this requires a sound application. There are several of these available as freeware. Search out Audacity which is a freeware product available for both PC and Mac. With it you can preview .wav files, adjust their length, balance, and probably lots else with .wav files. If you do and become an expert, please share your experience with other XP users here in this wiki.
Consider a twin engined plane such as a KingAir. The sound from the left engine should be stronger in the left ear. You can use a program such as Audacity to boost the left channel and quiet the right channel. do the opposite for the right engine (and prop, and starter). Now when you start up number 1, the sound in your headphones will mimic reality a little better.
Sounds and PlaneMaker
- Within PlaneMaker are 4 sound related questions; these are found by choosing Standard, then Engine Specs, then SFC/Sound. Down towards the bottom are the 4 questions.
- The first question has to do with wind noise in XP: obviously the sound caused by the wind will change with speed (increasing pitch with increasing speed) XP adjusts wind noise by changing the pitch of the wind noise sound with increasing aircraft speed. This first question asks what is the "Speed that wind sound was recorded at". If you have a custom wind sound you will need to know what speed (in KIAS, or Knots Indicated Air Speed) it was recorded at. The chances of you having all this info are small; it is usually sufficient to use XP's default wind sound and leave the value in this box at its default value of 200 KIAS.
- The second and third questions have to do with Propellor and Reciprocating Engine noise in XP: again obviously both Prop noise and engine noise will change with engine RPM.
It is difficult to get a handle on prop noise. First of all, in the real world, you rarely hear a prop turning without a noisy engine directly attached to it. I guess you could go out to a wind farm somewhere. You can find a lot of prop sounds out there and they sound strange when you play them straight. You will need to know what RPM your prop .wav was recorded at. Most of the sounds out there on the internet were done for MSFS; my guess is that knowledge of the frequency is not required in MSFS because none of these sound packages contain that info !!
In PlaneMaker, again choose Standard-Engine Specs-SFC/Sound. Down towards the bottom the second sound related question is "RPM that the propeller sound was recorded at". Keep in mind that propeller RPM and engine RPM will be different for geared engines. XP will play your custom prop sound "straight" at this prop RPM only; as prop RPM goes up and down it will adjust the prop sound pitch accordingly. For testing purposes you can consider making a special engine sound .wav with no sound, your engine will run but will not put out any noise, allowing you to hear the prop by itself.
On to reciprocating engines, i.e. piston engines either radial, in-line, opposed, whatever. Once again PlaneMaker will ask "RPM that the recip engine sound was recorded at" (third question, same place as wind and prop questions, Standard-Engine Specs-SFC/Sound). Again, there are lots of sounds out there, but very few will give info about what RPM the engine sound was recorded at. If you wish to isolate engine noise use the silent .wav trick discussed above, only this time apply it to the prop.
A general gripe with XP at this time is the quality of this particular aspect of the sim. In the future we might get the ability to put in two or three sounds over the RPM range to get better sounding engines. Round engines especially have rough throaty idles which don't smooth out until higher RPMs; the current system doesn't model this sound behavior very well, and if you are into round engines, this is unforgivable !
For now you need to know the RPM that your sound was recorded at or make an educated case using trial and error. The only way to hear the sounds is to fire up XP so trial and error can be a slow process. It is possible to download software to analyze .wav files and determine the fundamental frequency (which is not the same but related to RPM based on number of cylinders, two vs. four cycle, etc). If you find a sound you like you can analyze it to answer the sound questions ! As I recall, this was a huge pain in the rear as the UI for the software is difficult. The software is not free but you can download a one day free trial version (www.ymec.com). At this site they go through the exercise of determining the RPM of a Ferrarri at idle by analyzing the sound of the engine-pretty interesting. Another analysis package that seems easier to use (if only because you can open .wav files directly) is sigview with a one month trial period available at sigview.com.
Finally we get to turbine engines, turboprops, turbines, high bypass, etc. The fourth sound related question asks "N1 that get or turboprop was recorded at". N1 refers to the speed of the large fan or low pressure compressor section of a turbine engine (in general N1 refers to the speed of the first bladed rotor that air flowing into a turbine engine sees). All of the comments made for recips above apply here also. If you don't know this value you have to either guess or analyze. N1 is expressed as a percentage of maximum RPM, i.e. an N1 of 80% on an engine with max RPM of 25,000 would represent an RPM of 20,000. The answer to this fourth sound question is not an RPM but a percentage !
BTW, if your airplane has reciprocating engines, you can ignore the question about N1. If your airplane has a turbine engine, you can ignore the prop and recip questions. If you don't have any custom wind, prop, or engine sounds, leave the four questions at default values (200, 2500, 2500, 100)