I live in London and in my experience, the vast majority of problematic urban noise comes from two sources: overflying aircraft (mostly from to LHR and LCY airports), and modified or poorly maintained motorcycles.
Aircraft are improving with each generation but are still extremely noisy when they're directly overflying you, even many miles from the airport.
While there are certainly other sources of urban noise, like heavy goods vehicles and construction, these are strictly regulated and enforced with regards to operating times, etc in the UK - while noise from aircraft and private vehicles is not.
Sirens (fire, ambulance, police) can also be very loud, but I'll give them a pass because they are actually serving a useful purpose and saving lives. In the future when vehicles are quieter due to electrification, I think we'll be able to reduce the volume of emergency sirens too.
Those weird scallops on the back of all recent vintage Boeing planes are for noise reduction.
I couldn't find a quote or number on how many decibels it reduces the engines, except a note that:
| The acoustic liners and chevrons are such effective noise suppressors that several hundred pounds of sound insulation may be eliminated from the fuselage.
Aircraft are improving with each generation but are still extremely noisy when they're directly overflying you, even many miles from the airport.
While there are certainly other sources of urban noise, like heavy goods vehicles and construction, these are strictly regulated and enforced with regards to operating times, etc in the UK - while noise from aircraft and private vehicles is not.
Sirens (fire, ambulance, police) can also be very loud, but I'll give them a pass because they are actually serving a useful purpose and saving lives. In the future when vehicles are quieter due to electrification, I think we'll be able to reduce the volume of emergency sirens too.