If just walking on a treadmill and the noise was not annoying -it would not bother me at all. I think a lot better when I walk and I can listen so I can see where a treadmill would be a good thing. If she was running or huffing or messing with a heart rate monitor or such -then it would probably annoy me -but simple walking on a treadmill would not. I have a treadmill desk myself and used it while talking to clients etc on the phone