Which method is regarded as less effective for noise reduction?

Planting trees is considered less effective for noise reduction compared to other methods mentioned. While vegetation can provide some level of noise mitigation, particularly for high-frequency sounds, it generally does not offer substantial sound attenuation for lower-frequency noise, which is often more disruptive. The effectiveness of trees in blocking noise depends on several factors, including the type and density of the foliage, the height of the trees, and the distance from the noise source.

In contrast, creating berms and walls, implementing sound barriers, and increasing the distance from a noise source are all methods that more directly mitigate sound transmission. Berms and walls can block sound waves effectively, sound barriers are specifically designed for this purpose, and increasing distance helps reduce the intensity of the sound as it dissipates over distance. Therefore, while planting trees may contribute to an aesthetically pleasing environment and provide some benefits, it is not as reliable or effective for significant noise reduction as the other methods listed.