Noise barriers are solid obstructions built between roadways and residential areas. These barriers do not block all noise, they only reduce the overall noise level. Effective noise barriers typically reduce noise levels by 5 to 10 decibels (dBA). Subjectively, a 10 dBA increase in sound doubles the perceived or apparent loudness of a sound, while a decrease of 10 dBA halves the loudness experienced.

How effective are noise barriers?

When the line of sight is blocked between the noise source and the receiver, a reduction of a least 5 dBA is achieved. For each additional metre above line-of-sight, a reduction of an additional 1.5 dBA is achieved.

When are noise barriers required?

Ambient traffic sounds are everywhere, whether it is the daily hum of a busy street so loud that it limits normal conversation, or the roar of a vehicle that lost its muffler piercing through a residential street in the small hours of the morning. Traffic noise is the most pervasive and chronic noise to be faced in a growing urban region so heavily reliant on the automobile. For some, the volume and type of traffic close to their homes cause diminished home enjoyment.

Monitoring, testing, and evaluation are important tools in the management of traffic noise problems. Once the evaluation is complete, those areas that are deemed to have sustained noise levels above acceptable levels are scheduled for a sound attenuation project.

The impact of traffic noise on the listener can be reduced through the use of measures to block noise using berms and barriers. These may consist of built up earth mounds, or concrete walls or fences, with or without landscaping. Barriers may reduce roadway traffic noise levels by up to 10-15 dBA immediately behind the barrier.