In an Aural Task, the Signal and the Noise are different, but in a Statistical Task, they are similar.
Neither the lawn mower nor the sniffling would be confused with the speech signal, but they create a significant figure-ground task for the brain, which must internally suppress the racket while interpreting the speech.
The Statistical figure-ground task is even more challenging. This is a listening situation in which the figure and the ground are very similar.
Any teacher or parent who has tried to listen to two or more kids simultaneously telling about something that happened, will know the difficulty of this task.
During the second World War in England there were many instances when planes (many in dire distress) were returning from missions and requesting emergency landing instructions.