How great is the effect of trees on noise pollution?

I keep getting told that science tells us to use highway sound barriers and trees to reduce noise pollution. The effect that highway sound barriers has is quite immediately obvious but no matter how many trees I plant there never appears to be any noticeable effect on noise pollution.

The Cities: Skylines Wiki states:

A high level of noise pollution reduces land value and citizen happiness. Planting trees and creating roads with trees blocks noise.

This is similar wording to the tutorial tips in game however planting trees seems to have no effect on noise.

How great is the effect of trees on noise pollution?

As you figured out "normal" trees do not have an effect on noise pollution.

However roads with trees have ( a little ).

Sorry for the bad picture but you can still see Nr. 3 and 6 from the left.

• Report from users.
• Feature request on Reddit stating that this behaviour (normal trees reduce noise pollution) should be added to the game.

Noise pollution is created by traffic, industrial and commercial zones and tourist attractions such as the unique buildings. Smaller roads create less noise pollution and roads with decorative trees create less noise pollution than their tree-less counterparts.

This is a quote from the developers forums, taken from the dev diary. They don't say trees wouldn't help at all, however, they don't say that they would help too.

Considering all these sources, I think that trees don't help to reduce noise pollution. I just tested it myself: Trees didn't help. I don't know why the Wiki says it would be possible although a lot of people say it clearly isn't.