Dog Barks when I am on the phone

Hello, I’ve noticed something with my dog that’s been happening ever since I can remember. She is 3 years old and a mini schnauzer

She always starts barking when I am on the phone with someone and will not stop until I get off the phone call. Once I am off the call she stops barking.

It doesn’t matter if I’m taking the call next to my ear, on speakerphone, or on my AirPods. If it is someone she knows, she doesn’t respond any differently- even if they talk to her through the phone (and she knows their voice).

Giving her attention during the phone call like picking her up or calling out her name also doesn’t help.

I’m wondering if there is a possibility that the phone calls are somehow painful for her? Like she can hear something I can’t ?

Please help!