In the Noise Barrier Design Guide, the following acoustics principles are discussed in relation to their effectiveness on noise barrier design.  A brief summary is provided below.

• Location - In principle a noise barrier is most effective located as close to the road as possible. However, for a road located in a cutting it is better to place the barrier at the top of the cutting, where it will have a greater effect.
• Height - Generally the higher the barrier, the greater the level of noise reduction. As a general rule, a noise barrier should at least be high enough to block the line-of-sight from a house to the engines of vehicles on a road.
• Reflection - Multiple reflections between parallel noise barriers, or between barriers and high sided vehicles, can reduce the benefit of a barrier. It is possible to reduce the acoustic reflectivity of a noise barrier by using an absorptive material (e.g. mineral wool or fibre glass) with an appropriate facing.
• Top shape - Modifying the shape of the top edge of a noise barrier can increase the performance of the barrier without increasing the height and associated visual impacts. Shapes include T-tops, Y-tops, pear-shaped tops, cantilevered walls and others.
• Bunds - Where space is available, bunds (which are a form of noise barrier) can be a more attractive solution, either on their own or with a wall type barrier on top of the bund.
• Length - Some sound may 'bend' around the ends of barriers. As such, the length of a noise barrier is important. A rule-of-thumb to determine the required length of a noise barrier is that it must cover a horizontal angle of 160 degrees viewed from the receiver.
• Continuity - In order to be effective, noise barriers must be continuous over the required length, with no vertical or horizontal gaps. In practice this is not always possible. Overlapping walls can be used to resolve this issue.
• Materials - For noise reduction greater than 10 dB, or where the barrier height is over 2 metres, barriers should generally be constructed of materials that have a surface mass of at least 10 kg/m² and are built with no gaps.
• Vegetation - Typically vegetation is not an effective noise barrier. A 30 metre wide strip of dense trees may only reduce noise by up to 5 dB where it obstructs the line-of-sight between the source and receiver
• Wind - Certain downwind conditions can reduce the effectiveness of a noise barrier, as sound is 'bent' over the top of the barrier by the wind. The presence of a row of trees behind a noise barrier in such situations may improve the downwind performance of a barrier.