The frequency is evolutionary tuned to maximize discomfort for most mammals.
This is a really cool fact, can I ask where you found it? I tried searching for a few variations of “max discomfort frequency scream mammals,” “scream deter mammals” and the like, and I am not finding this anywhere.
Curious because if true it might be useful to keep wildlife away from your house, or to know to avoid (or approach, if you’re trying to cause discomfort) if you’re a musician composing a piece.