white noise from MacBooks speakers for output and input usb microphone?

Why can't I play accessibility app with noise from a different output then I am inputting sound into my Air? I I want to use this feature to play white noise while recording using an external USB microphone. This is one of the main useful applications of the white noise feature that I can think of, to have it provide privacy while capturing your words, and using a different input, which would help ensure that the white noise is not actually heard much in the recording, especially with long cables putting the computer by the door and the microphone boom on the other side of the room.. better placed for privacy as intended. but no, the white noise- It automatically stops when you have a different input and no longer allows you to turn on white noise. I hope I am missing something though and am wrong about this, as it would be very helpful and Ive of course been wrong countless times before.

This weird obscure tech person only over everyday usefulness approach seems to be apples order of the day, the developmental features are all things that make no sense to me or that I can't even comprehend and yet I cant use white noise for privacy while recording a lecture! Im so sick of having to do workarounds, buy a new dongle or cable or item every time I want to do something outside of the exact box apple designers seem to think in. that's how it is anymore. I am scouring best buy and amazon twice a week for a work around to use my 1500 dollar computer for something I was certain would be included features.