When I see LIGO graphs they always appear linear - the change in frequency is linear with time. But with time dilation as black holes near each other, shouldn'

When I see LIGO graphs they always appear linear - the change in frequency is linear with time. But with time dilation as black holes near each other, shouldn't the frequency change be exponential? Or does it cancel out - the frequency goes up as they get closer, and then time dilation lowers it back as it dilates into infinity?