[WalterBright]

> such that a name like “jack” wouldn’t even register to them

My experience disagrees. I often have a back and forth "conversation" with my cat, and she clearly responds to my voice, which is not high pitched.

[a3n]

But you still produce high frequency sounds: the "clicks" and such that differentiate consonants, for example.

The cat may be responding to those discrete high frequency sounds, rather than your overall voice.