Didn't watch the video but what I learned with our last two was that the shushing works because in the womb the baby is used to hearing the body sounds especially heart and blood flow sounds and shushing mimics that. But it has to be loud because it is loud in the womb. Makes sense I guess because with no air in the womb a baby can't cry there so to take it back to the womb takes it back to where it is safe, dark and warm and there is no crying.