FShift
Specifies the percentage delta in frequency shift applied downwards and upwards, to the sound when played. Parameters should contain 2 values, the minimum frequency delta and maximum frequency delta respectively.
You can more easily think of this as slowing down and speeding up the sound being played, so "FShift=-10 10" would mean the sound will play between 10% slower and 10% faster than normal.
The main use case for this is where a sound object only has 1 wave file resource, thus lacking in randomness, and every time it is triggered, such as the DogAttack, that a slight pitch change will be applied, making it seem like they are all a little different. A more obscure use case could be to get female civilian voices to sound like male voices, by slowing them down using negative FShift values for both min/max.
Note: frequency shifting can be quite aggressive, high values should be avoided in sound.ini