I thought this was already in planes, such as Dash 8 (Q400) -- noise cancellation, although for the general cabin, not the individual seat passenger: https://w

I thought this was already in planes, such as Dash 8 (Q400) -- noise cancellation, although for the general cabin, not the individual seat passenger: https://www.flightglobal.com/quiet-revolution/31793.article https://www.flightglobal.com/quiet-revolution/31793.article https://apps.dtic.mil/sti/pdfs/ADA446777.pdf https://apps.dtic.mil/sti/pdfs/ADA446777.pdf (see plots at end)