Is the noise on approach an issue anyway? Isn't it very low when compared to a take-off?
Not at all - in fact, quite the opposite. Very counter-intuitively, approach noise can be as much as 10 EPNdb greater than that of takeoff. Airframe and flap generated noise has much more of an impact than you'd think!
As QantasA332 says.
It's also important to remember that it's not noise in absolute terms, ie how loud the plane is objectively, that really counts. It's perceived noise on the ground. When an airliner is climbing out, it does so rather steeply, and thus the noise on the ground has a limited footprint. Coming in for landing at a shallow angle keeps the plane close to the ground longer, waking up more NIMBYs.
This noise footprint issue is the reason why more modern aircraft do not derate as much at SNA
, for example. By using higher power settings they can get up to altitude faster. While they objectively make more noise, they make a larger proportion of the noise further from the NIMBYs, and thus the perceived noise on the ground is less.
Same with winglets on the 727. These allow the 727 to be certified for takeoff at airports where it would normally be banned for noise. The winglets don't make the airplane any quieter but allow it to climb out of hearing range faster.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo