Daybreak in the city. The brief quiet of the night gives way to the low rumble of cars, trucks and industry, but one sound is notable by its absence. Gone is the familiar dawn chorus, with its rich mix of enchanting melodies and calls. In its place is a strangely depleted music - abrupt, high-pitched and sometimes ear-piercing. Welcome to the urban soundscape of the future.This is no dystopian vision. It is the prediction of scientists who have been studying the way in which noise pollution affects urban bird life.