[unity1001]

The youtube video has links to various ones in the description. But you have to follow the posts to get to the actual research. Here are some:

https://www.atsjournals.org/doi/full/10.1164/rccm.200202-138...

https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2362....

https://www.researchgate.net/publication/343237144_Role_of_N...

https://www.atsjournals.org/doi/full/10.1164/rccm.200202-138...

...

When you try doing it, you start noticing a strong smell that smells like early spring or the smell certain air purifiers make. This smell lasts as long as you keep humming.