An investigation of infrasonic in traffic flow noise

The society is aware of traffic noise and participates with local municipalities and cities in solving the noise problems. Positive economic indicators can be achieved when health is good. One of the important factors is restful sleep, which can be interrupted by traffic noise. The increased use of wind energy by windmills and various modes of transportation could increase the low frequency sound that could have a negative effect on the population. When humans are exposed to low frequency sound, only the high sound can be heard. The low intensity infrasonic sound could affect human health and induce various psychological disorders. The infrasonic sound could travel long distances and penetrate the openings in a welling occupied by humans and interrupt rest and sleep. The infrasonic measurements were performed using the Bruel & Kj ae r instrumentation. Components of infrasonic energy frequencies were obtained by calculating the difference between the averaged sound pressure level and the A-weighted sound pressure level. Aerodynamic turbulent noise propagations over ground are affected by diffraction from jaggedness and stress viscosity from secondary sound sources. The noise barriers are effective in the diffraction process by reducing noise to the living environment. Measurements were performed using acoustic barriers for traffic noise reduction in the suburbs. At 15 m from the highway, a 2 m high barrier was constructed and the measurements were taken at 15 m and 45 m from the barrier. More intensive sound diffraction was observed at the measurement distance of 45 in. These observations indicate the importance of infrasonic diffraction and of the design of acoustic barriers for the reduction of low frequency noise.