A review of road traffic barriers for low frequency noise

Australia relies heavily on road transport due to its large area and low population density in many parts of the country. Trucks and heavy vehicles are commonly used for road freight. In addition to their normal vehicle brakes, heavy vehicles are typically fitted with release engine brakes which operate by causing the engine to act as a compressor when braking. Compression braking generates a distinct low frequency rumble that can be heard at large distances and is a major source of community annoyance reaction against the heavy vehicle industry. Noise from compression brakes is an on-going cause of complaint from many Australian residents, particularly in rural areas and at night-time. Noise barriers can be used to reduce the spread of general traffic noise and their effectiveness is determined by many factors. This paper presents a review of barriers optimised for road traffic noise, with a view to selecting barriers that may be more effective at reducing the low frequency and modulation characteristics in the noise from compression brakes.