In the simple version you need only one parameter – the RPM of your aircraft’s engine. The RPM should be normalized to 0-1 range. Where 0 – is an IDLE engine, the engine after the startup sequence. And 1 – is a MAXIMUM engine power of your aircraft’s engine.

Use 5 sounds: Startup_Simple and Shutdown_Simple (at will), Idle, Maximum and Distant_Simple sound. If you need to separately sound the cockpit, then use the following sounds: Startup_Simple_cockpit, Shutdown_Simple_cockpit, Idle_cockpit, Maximum_cockpit and Avionics_cockpit. Avionics_cockpit should be always with pitch and gain = 1.

If you want to use the sounds of Startup_Simple and Shutdown_Simple (cockpit versions: Startup_Simple_cockpit and Shutdown_Simple_cockpit), then just play the sounds when it is necessary and limit the control of the aircraft to the user for the length of the startup and shutdown sounds respectively. Make sure all other sounds are turned off while playing Startup_Simple and Shutdown_Simple sounds. Immediately after the Startup_Simple sound, the rest of the sounds should be started with the gain and pitch for RPM = 0.

Let’s display the parameters of the gain and pitch of the other sounds we need in the table:

For Example:

Our aircraft is flying at a RPM = 0.85.
Let’s calculate the volume and pitch of Idle sound:

Idle.gain = -0.3 * RPM + 1 = -0.3 * 0.85 + 1 = 0.745
Idle.pitch = 0.382 * RPM + 1 = 0.382 * 0.85 + 1 = 1.3247

In the same way calculate the parameters for others.

For the sound of jet planes it is very important from which side we look at it. The sounds from the front and rear of the aircraft are very different. Therefore, in the advanced version, we must separately sound both sides.

There are 13 sounds for advanced version: Startup, Startup_Front, Startup_Back and Shutdown, Shutdown_Front, Shutdown_Back (at will), Idle, Idle_Front, Idle_Back and Maximum_Front, Afterburner_Back, Distant and Distant_Back sounds. If you need to separately sound the cockpit, then use the following sounds: Startup_cockpit, Shutdown_cockpit, Idle_cockpit, Maximum_cockpit, Afterburner_cockpit and Avionics_cockpit. Avionics_cockpit should always be with pitch and gain = 1.

As in the simple way for the advanced way we need engine RPM, normalized to 0-1 range and SPEED of aircraft for distant sounds. Distant sounds (Distant and Distant_Back) should not be heard at low speed. Therefore, for all distant sounds, after calculating the volume from RPM from the table below, add a multiplier when the SPEED is below 400km/h:

Thus, the volume of the distant sounds will drop to zero when the speed drops below 400 km/h.

If you want to use the sounds of Startup and Shutdown, then limit the control of the aircraft to the user for the length of the startup and shutdown sounds respectively. And play Startup, Startup_Front, Startup_Back (for cockpit — Startup_cockpit) sounds for startup and Shutdown, Shutdown_Front, Shutdown_Back (for cockpit — Shutdown_cockpit) for shutdown. Make sure all other sounds are turned off while playing these sounds. Immediately after the startup sounds, the rest of the sounds should be started with the gain and pitch for RPM = 0.

The Afterburner sounds should play only when the RPM is more than 0.95.

Let’s display the parameters of the gain and pitch of the other sounds we need in the table:

To understand how to use it – see an example for a simple implementation.

Create 2 audio mixer groups: front_group and back_group. Then assign the sounds “…_Front” and “…_Back” to the appropriate audio mixer groups. Then you need to calculate the angle between your sound source (your plane) = “from” and the sound listener (camera) = “to“.
For example in Unity C#, it would be:

n_angle will be equal to 1 when we look at the plane from the front, and will be equal to 0 when we look from behind.
Now we can control the loudness of our audio mixer groups:

Thus, the volume of the front_group will be equal to 1, and the volume of the back_group will be equal to 0 when we look at the aircraft from the front. And the volume of the front_group will be near 0, and the volume of the back_group will be equal to 1 when we look at the aircraft from behind.

It is important to properly limit each sound radius for the greatest realism. The minimum distance is the radius of sound with constant volume = 1. The maximum distance is the radius beyond which the volume of the sound is = 0.

If you need, you can calculate the volume of the sound on any distance between minimum and maximum:
Distance_Volume = (distance — Min_Distance)/(Max_Distance — Min_Distance)