This is the planning link. It's a 'building control' application, which I think means no changes to the external appearance of a building, just changes inside. There are no details.
23/06298/IN | Extension of existing first floor slab and associated infrastructure works at pier B | Pier B Luton Airport Airport Way Luton
I live near the flight path and I do think the Airbus NEOs are quieter, the sound is different and the noise falls away faster as the plane moves away.