Yes the current aircraft sounds might be limited to mono and 22500KHz, but the actual sound engine is surprisingly good. I was able to add much more realistic sounds to the jets, and it was a fairly quick process.
I'm sure most of you have quite a few addons for P3D or FSX with pretty good sounds. Luckily those addons use WAV sound files - that's the raw format required by the AFS2 converter tool. So, here is a brief tutorial of how you can create your own sounds for any aircraft in AFS2:
Obviously you'll need the SDK and the aircraft conversion tool installed to do this - please do that first if you haven't done so already.
1) Identify the number of engine sounds for the specific aircraft you'd like to create sounds for. Let's have a look in your C172 folder (under /Aerolfy FS 2 Flight Simulator/Aircraft). We're looking for files with .tsb extension. With the Cessna you'll find quite a few .tsb files but their name is a perfect hint. For example ext1000rpm.tsb means the external sound file for 1000RPM. There is 6 internal and 6 external engine sounds for the cessna for 6 different RPM ranges. However, the cessna sounds are pretty spot on, so let's "update" another aircraft. We all love the A320, don't we? Unfortunately the sounds it comes with don't really do it justice. So, again, have a look in its folder and search for .tsb files. As before, based on the file names there are basically 2 X 3 files (3 for external and 3 for internal), with names like idle, half, and full. There is also a reverse thrust one, but let's focus on the internal ones for now, those three .wav files for idle power, half power and full power.
2) Getting raw sound files is pretty simple: go to AVSIM, or Flightsim.com and download a freeware soundpack, or use any 3rd party soundsets you purchased before, then choose the appropriate .wav files from them that will represent those 3 power settings.
3) Now we'll have to make sure those .wav files are prepared for conversion. First let's rename them as per the original files. For example the sound file you chose for the idle engine sound should be called "a320-idle-intern.wav". In other words, give them the same name as the tsb file only with wav extension.
For the rest of the sound preparation tasks I'll use Audacity, but you're free to use your favorite sound editor. For each sound file do the following: "
- Open the file in Audacity
- Click on "Stereo Track to Mono" on the Tracks menu at the top of the window
- Click on "Resample..." on the Tracks menu and choose 22500
- Click "Export..." in the File menu, provide a file name, and choose "WAV (Microsoft) Signed 16bit PCM" as the format
Once you completed these steps for all files, they will be ready to be converted
4) We'll create a folder under the /aricraft_workshop directory of the SDK root folder. Make sure you only use lower case and numbers for the name of this folder. I'm going to use "sound001" for simplicity. Now, copy the prepared wav files into this folder, and also copy the following 3 files from the /dr400 folder (that's also in the aircraft_workshop folder): model.tmc, dr400.tgi, dr400.tmd. This is all you need for the sound conversion.
5) Now, right-click the sound001 folder (with the raw files in it) and choose the "Aerofly FS 2 Aircraft Converter" from the pop-up menu. You can click on the green Convert button - however you won't need to wait till the whole conversion process finishes though. The converter will start with the WAV files luckily, so when you see it working on things like "geometry" that means the sound files are already converted, so you can click on EXIT.
6) You'll find your converted files here: C:\Users\<username>\Documents\Aerofly FS 2\aircraft\sound001
7) Create a backup of the sound files you're about to replace (under <AFS2 root>\aircraft\a320\). In this scenario we'll replace the 3 internal engine sound files: a320-idle-intern.tsb, a320-half-intern.tsb and a320-full-intern.tsb. BACK THEM UP! No really, back them up!
Now you can copy and overwrite the original .tsb files with the ones created by the conversion tool (from C:\Users\<username>\Documents\Aerofly FS 2\aircraft\sound001 into <AFS2 root>\aircraft\a320\). I'd recommend that you delete the sound001 directory (the one under your Document folder) after you copied the files from it so there won't be any mix-ups with other sound files you might convert later - this way you always start the conversion with a "clean slate".
9) Test your sounds. Load up the plane and try all power settings. I found that the AFS2 sound engine does a great job with aligning them and combing them together seamlessly.
That's pretty much it. If you want to make some adjustment (volume, EQ) do that on your raw files and convert them again. Once you get used to the process it won't take more than 5-6 minutes including testing.
You can customize all aircraft sounds using this process, not just the engine sounds. However, it's important that engine sounds have to be infinite loops, while others (like the autopilot disengage sound for instance) don't need to be looped.
In case you have any questions or my explanation wasn't clear on a certain step, let me know.
PS: If you screwed up the back-up step, you can always use the Steam File Integrity check to restore the factory files.