Rufin Makarewicz

A MODEL OF INTERRUPTED ROAD TRAFFIC NOISE

Freely flowing road traffic is interrupted by a stopping line. Traffic is mainly from light vehicles, because the number of trucks, buses, etc., is negligible. Vehicles are cruising or stopping, and the traffic flows in both directions is approximately equivalent. The theory discussed in the present study enables us to predict the time-average sound level, LAT, when the distance between the stopping line and the receiver exceeds the road width, acceleration length, and the length of the vehicle’s queue. To estimate the adjustable parameters of the model, two simultaneous measurements of LAT at the site of interest are required.

RAILROAD NOISE IN AN OPEN SPACE

Abstract The model presented here allows prediction of the sound exposure level ( l ae ) and the time-average sound level ( L AeqT ) of noise, generated by trains moving with a steady speed in an open space. The receiver is assumed to be so close to the track that geometrical spreading is effected principally by the ground effect. A real train is modeled by a homogeneous line of point sources with dipole directivity. To fit the time asymmetry of the time history of noise level which is produced by a high-speed train, a ‘virtual source’ has been introduced. The free parameters of the model can be estimated from two simultaneous measurements of lae at distances of D 0 and 2D 0 , respectively.

A SIMPLE MODEL OF OUTDOOR NOISE PROPAGATION

Abstract A simple model of ground effect and turbulence, which are disturbed by other wave phenomena, is developed. This model makes it possible to predict the sound level, L A , of noise from a stationary source (i.e. industrial noise) and the time-average sound level, L AeqT of noise from moving sources (i.e. road traffic). To estimate the free parameters of the model, three simultaneous measurements of L A or L AeqT , at the site in question, must be performed.

Influence of ground effect and refraction on road traffic noise

Abstract Ground effect and refraction modify geometrical spreading. In the present study a simplified model of ground effect is applied. Refraction is analyzed for the motionless atmosphere with a linear sound speed profile. Noise generated by constant speed road traffic is assessed by the time-average sound level, LAeqT-. The model of LAeqT prediction contains free parameters that are estimated from noise measurements at the site in question. The model makes possible the prediction of LAeqT at an altitude of a few tens of meters above the ground surface, within the range of a few hundred meters from the road. Contours of LAeqT = constant in the vertical plane represent the radiation pattern of road traffic noise.

Impact of refraction on train noise

Abstract In the present study, a special case of refraction due to wind blowing along the track is considered. Turbulence caused by wind eddies destroys the coherent nature of the ground effect. Due to upward refraction and the resulting shadow zone, only a segment of a track contributes to the noise in the receiver. The model contains three adjustable parameters that must be estimated at the site of interest.