As of RealFlight 6.00.044 (public beta) released on April 25, 2012, RealFlight allows for the use of custom motor sound profiles. This guide will explain the basics of recording, editing, and importing a custom motor sound profile.
Setting up your recording environment
Make sure you have the necessary hardware:
You'll want to use a good microphone to capture your motor sounds. A good microphone is one with good frequency response--one that equally captures all the high and low sound frequencies your motor makes. There are more aspects of microphone quality to consider, but that goes outside the scope of this guide. Consider a microphone with a wind screen to avoid picking up unwanted noise both from wind and from airflow generated by the aircraft.
It is a good idea to use a mic stand to mount the microphone during the recording process. This makes it easier to position and orient the microphone precisely where you want it. Avoid fixing the microphone directly to the motor or aircraft's fuselage, as this will introduce a lot of unwanted vibration noise into the recording. Also avoid holding the microphone by hand during recording, as this can introduce similar vibration/rubbing noises into the recording, as well as change the sound characteristics of the recording as the microphone moves around slightly.
You'll need a way to record the sounds in a digital format, either directly onto your computer, or onto a portable device so they can be transferred to your computer afterwards.
A tachometer is useful for measuring the exact RPM of your motor during the recording process.
You'll need to find a good location to record your motor. As much as possible, you must isolate the motor sound from all other noise. Recording outdoors often means you're fighting with the sounds of wind, wildlife, automobiles, full-scale airplanes flying overhead, etc. You may have a successful recording session if you can find a quiet outdoor area with little to no wind and minimal background noise. Recording indoors usually offers less background noise, but it also tends to carry the problem of short echoes coming from sound waves bouncing off the walls. This can result in resonant frequencies lingering in your audio recording, depending on the size of the room in which you're recording. Ideally, recording is best done in a professional studio with proper sound damping material mounted on the walls to absorb the echo. If you're on a budget, you can try replicating this setup at home by mounting unwrapped sleeping bags on the walls of a small room.
Note that a skilled digital audio producer can alleviate some of the echo and noise problems after the recording process is done, but it's generally much easier and less time-consuming to avoid these problems in the first place.
Recording your motor
You'll need to record your motor running at various RPMs--the highest it is capable of, the lowest, and several points in between. We recommend creating a single long recording of your motor stairstepping from its lowest RPM to highest (or high to low). The RPM should remain unchanged except when transitioning to the next value you want to record. The goal is not to record those transitions between RPM values; the sim will handle that automatically. The goal is to capture steady examples of discrete RPM values throughout the motor’s operating range.
There are many things to keep in mind for this process:
Editing your recording
Once you've transferred your recorded audio to your computer, you'll need to edit your recording and prepare individual RPM samples for importing into RealFlight. This requires audio editing software. Audacity is a free audio editor and is available for download at http://audacity.sourceforge.net/ There are numerous commercial audio editors available as well, with varying levels of features.
The overall goal of the editing process is to separate your one long recording into several individual looped samples--one for each RPM you recorded. The individual samples can be saved either in .wav format or in .ogg (Ogg Vorbis) format, but all samples for a single sound profile must be saved in the same format. Ogg Vorbis audio files will have negligibly lower sound quality but will be much smaller in file size. That means dramatically smaller .RFX file sizes, so we recommend using the .ogg format.
Each individual sample should have a filename that matches the RPM it represents. For instance, a sample of a motor running at 4250 RPM should be named 4250.ogg or 4250.wav. Only numbers are allowed in the filename.
There are a handful of other things to keep in mind when editing each individual RPM sample:
Importing your sound profile into RealFlight
Once all your individual edited samples have been saved to the same folder, in the same file format, and with proper filenames, you can import them into RealFlight and create a new sound profile. Do this by clicking the "Simulation" menu, then "Import", and then "Motor Sound Profile...". The resulting import wizard will guide you through the import process.
Setting up your recording environment
Make sure you have the necessary hardware:
You'll want to use a good microphone to capture your motor sounds. A good microphone is one with good frequency response--one that equally captures all the high and low sound frequencies your motor makes. There are more aspects of microphone quality to consider, but that goes outside the scope of this guide. Consider a microphone with a wind screen to avoid picking up unwanted noise both from wind and from airflow generated by the aircraft.
It is a good idea to use a mic stand to mount the microphone during the recording process. This makes it easier to position and orient the microphone precisely where you want it. Avoid fixing the microphone directly to the motor or aircraft's fuselage, as this will introduce a lot of unwanted vibration noise into the recording. Also avoid holding the microphone by hand during recording, as this can introduce similar vibration/rubbing noises into the recording, as well as change the sound characteristics of the recording as the microphone moves around slightly.
You'll need a way to record the sounds in a digital format, either directly onto your computer, or onto a portable device so they can be transferred to your computer afterwards.
A tachometer is useful for measuring the exact RPM of your motor during the recording process.
You'll need to find a good location to record your motor. As much as possible, you must isolate the motor sound from all other noise. Recording outdoors often means you're fighting with the sounds of wind, wildlife, automobiles, full-scale airplanes flying overhead, etc. You may have a successful recording session if you can find a quiet outdoor area with little to no wind and minimal background noise. Recording indoors usually offers less background noise, but it also tends to carry the problem of short echoes coming from sound waves bouncing off the walls. This can result in resonant frequencies lingering in your audio recording, depending on the size of the room in which you're recording. Ideally, recording is best done in a professional studio with proper sound damping material mounted on the walls to absorb the echo. If you're on a budget, you can try replicating this setup at home by mounting unwrapped sleeping bags on the walls of a small room.
Note that a skilled digital audio producer can alleviate some of the echo and noise problems after the recording process is done, but it's generally much easier and less time-consuming to avoid these problems in the first place.
Recording your motor
You'll need to record your motor running at various RPMs--the highest it is capable of, the lowest, and several points in between. We recommend creating a single long recording of your motor stairstepping from its lowest RPM to highest (or high to low). The RPM should remain unchanged except when transitioning to the next value you want to record. The goal is not to record those transitions between RPM values; the sim will handle that automatically. The goal is to capture steady examples of discrete RPM values throughout the motor’s operating range.
There are many things to keep in mind for this process:
- Clipping occurs when the sound is louder than the microphone is able to record, resulting in distortion. Your recording setup should have a microphone input sensitivity control. Set it to the highest level you can find that does not allow clipping. You should be able to record your sound source at its loudest moments without the levels going into the red (if you have meters) or otherwise triggering a clipping indicator. Reduce the sensitivity as needed until you can accomplish this.
- Do not adjust the microphone sensitivity during a single take. Motors are louder at full throttle than at idle. Let the lower RPM values be naturally quieter in your recording, as well.
- Put the microphone close to the motor. This will help you maximize the proportion of sound you get from the motor versus unwanted echoes and background noise. However, placing the microphone too close will result in the "proximity effect", where lower-frequency sounds are exaggerated. It may also result in clipping, which should always be avoided. Try different distances to see what sounds best.
- Try recording from different angles as well. Recording from above the sound source may sound noticeably different than from the side. Again, experiment with microphone placement to find what sounds best.
- A rule of thumb for determining the spacing of different RPM values to record is that each RPM should be about 25% higher than the one below it. For example, if you record a steady 4500 RPM as one of your “stair steps”, we recommend trying to record the next one at around 5625 RPM. If you have a musical ear, this translates to about 4 semitones, or a major third. Again, this is just a rule of thumb and does not need to be exact. You can record with denser or sparser gaps between RPMs if you like. There is no point getting values too close to each other, however. Allow some room between the samples or it might actually sound worse in the end.
- Record each steady RPM for at least 10 seconds. The RPM should not vary during this time. The longer you record, the easier it will be for you to find a suitable section for looping later.
- If you are recording a battery-powered electric motor, the maximum attainable RPM will drop almost immediately as the battery begins losing its charge. For this reason, you should start your recording with a fully charged battery, and you should record the highest RPM first. Note that even with this approach, the maximum RPM is likely to drop slightly while you attempt to record it. You can try to fix this later during the editing process, or you can record an RPM just barely less than the motor's maximum to avoid the slow drop in RPM.
- If you have a tachometer, remember to measure the exact RPM of the motor for each sample. It may be easiest to vocally announce the RPM after each sample in the audio recording, and then refer to that later during the editing process.
- Avoid recording to a compressed audio format such as MP3. This will help preserve the quality of the recording during the editing process.
Editing your recording
Once you've transferred your recorded audio to your computer, you'll need to edit your recording and prepare individual RPM samples for importing into RealFlight. This requires audio editing software. Audacity is a free audio editor and is available for download at http://audacity.sourceforge.net/ There are numerous commercial audio editors available as well, with varying levels of features.
The overall goal of the editing process is to separate your one long recording into several individual looped samples--one for each RPM you recorded. The individual samples can be saved either in .wav format or in .ogg (Ogg Vorbis) format, but all samples for a single sound profile must be saved in the same format. Ogg Vorbis audio files will have negligibly lower sound quality but will be much smaller in file size. That means dramatically smaller .RFX file sizes, so we recommend using the .ogg format.
Each individual sample should have a filename that matches the RPM it represents. For instance, a sample of a motor running at 4250 RPM should be named 4250.ogg or 4250.wav. Only numbers are allowed in the filename.
There are a handful of other things to keep in mind when editing each individual RPM sample:
- Each sample should be around 7 seconds in length.
- Make sure the sample sounds good when looped on repeat. There is often an audible "pop" when looping between the end of a sample and the beginning due to slight phase differences. This problem can generally be eliminated through trial and error by repeatedly shaving a few milliseconds of audio from the beginning and end of the sample until the loop sounds smooth.
- Listen to the sample on repeat many times for artifacts and unwanted noises. Sometimes it can take a while to find an annoying subtle "squeak" or "thud" that made its way into your recording, but once you notice it, you'll hear it constantly. These artifacts can be eliminated with the use of equalizers and other editing techniques not covered by this guide.
- Be sure the RPM in the recording matches the name you give to the file. RealFlight crossfades between different samples at intermediary RPMs, meaning two samples are often playing simultaneously. If one of them is assigned an accurate RPM but the other is not, you will hear the very dissonant sound of two slightly different tones being played together instead of blending properly. Advanced users can generate a reference tone in the audio editing software to check against. For example, if you expect your sample is 9000 RPM, you can divide 9000 RPM by 60 seconds to get 150 Hz. Generate a 150 Hz tone in the audio editor and play it alongside your 9000 RPM sample. If the two sounds played in tandem sound dissonant, or make noticeably different tones, your sample is probably not actually 9000 RPM.
Importing your sound profile into RealFlight
Once all your individual edited samples have been saved to the same folder, in the same file format, and with proper filenames, you can import them into RealFlight and create a new sound profile. Do this by clicking the "Simulation" menu, then "Import", and then "Motor Sound Profile...". The resulting import wizard will guide you through the import process.
