Hello,
In airplanes, as the aircraft climbs to higher altitudes, the engine sounds fade into the background due to the atmosphere becoming less dense. During cruise in airliners, the only sounds heard are the wind sound in the cockpit. This is not currently represented by the Prepar3d sound engine as the engine sounds are solely based on the Volume and Rate parameters in the sound.cfg. The sound values for engine sounds do not change with altitude as they would in a real aircraft. Many third party developers have worked around this by using .gau sound files that include many more parameters than simply the rate/volume params. Updating the Prepar3d sound engine to natively include more parameters would help developers simplify the development of accurate sounds in certain scenarios.
The simplest way I see this being implemented would be an additional parameter in the sound.cfg file. This 'altitude parameter' could act as an overall volume of the specific sound file that the cfg could apply before then applying the appropriate rate and volume parameters. Having 3 to 4 inputs would be useful with a default to a linear scaling of the parameter.
For example, Alt param= (0,1.0)(10000,0.75)(40000,0.35).
In this example, the specified sound file would play at a volume adjustment factor of 1.0 at 0 feet sea level with a linear decrease to 75% once at 10,000 and then an additional linear decrease to 35% by 40,000feet.
