It's true, airplanes are loud. That is the unfortunate consequence of having the convenience of an airport nearby. There may be many reasons for that convenience, but it typically always outweighs the noise annoyance. Those that don't like the noise pollution can take steps to avoid it. On the other hand, there is other pollution produced by airplanes that are of far more importance to be addressed
I think airlines have done enough to reduce noise pollution from their jet engine. Also, it will keep on improving as our technology continues to improve. The noise from jets is mostly not heard, and really only bothers people who live close to airports. So no, I don't think they should take steps to reduce it.
Airlines should not do more to reduce noise pollution from their jet engines. To attempt this would mean having to do expensive blueprints and modeling and creating new airplane parts. This would end up directly costing the consumer more in air fare than they are already charged. The noise pollution is not that bad enough to warrant such changes.
Just like driving a car on the government's roads, you need to get permission to fly in the government's skies. The FAA has been actively working with airlines to reduce noise emissions since the 1960's (and they have to a large extent succeeded in spite of increased air traffic). It is naive to expect the airlines to make this costly changes of their own volition, especially since it is unlikely to result in increased revenues. In cabin noise has already been reduced below nuisance level. Customers are not likely to pay higher fares simply to make things quieter for strangers living around the airport.