The obvious thing for the airport to do is to take sound measurements from the garden which no doubt they would be reluctant to do. Luton is no different, they take noise readings 6.5km from the end of the runway. If airport employees were working in her garden they would be mandated by law to wear ear defenders if the noise levels reached 85dB. So what is the noise level there? The truth is I would think they have no idea and don't want to know either.