What strategy is considered ineffective when planning noise barriers?

Constructing barriers far from noise sources is ineffective because the primary goal of a noise barrier is to intercept and reduce the sound transmission from the source to the receptors (the people or structures that need protection from the noise). The closer the barrier is to the noise source, the more effective it will be at reducing the intensity of the sound that reaches the intended audience.

Barriers that are placed at a significant distance from the noise source will have diminished ability to block or absorb sound, as sound waves can disperse and lose energy over distance. Therefore, the effectiveness of any noise abatement strategy relies heavily on the proximity of the barrier to the source of the noise.

In contrast, using barriers of greater mass, ensuring they block the line of sight, and creating continuous structures can all enhance the effectiveness of the noise barriers. Greater mass helps in sound absorption and reflection, while blocking the line of sight can further prevent sound from traveling directly to the receptors. Continuous structures reduce gaps where sound can leak, thereby helping to ensure sound reduction is maximized.