I'm still real lost... I first thought "hearing no beat" means I should set the beat frequency to zero because f1 needs to equal f2 for that to be true, but that doesn't make any sense if I use that to try and solve for running speed..? What conditions need to be met in order to hear no beat?
I found the beat frequency to be 4 Hz and the carrier frequency to be 260 Hz, but I'm not sure how to apply them to the solution/integrate the doppler and beat frequency equations?