To evaluate the efficacy of the predictive computer programs used to design the barriers, noise measurements were taken before and after construction of an earth berm and plywood wall alongside I-495 in Northern Virginia. The effect of the barrier was taken as the difference between the before and after drop-offs in noise levels from the roadside to the location under study. The measured effects were compared to the predicted effects. Less than half of the measured effects were within 3 dB of the predicted values. However, when the effects of the time of day and human activity within the neighborhood were taken into account, 65% of the noise values obtained during periods of low human activity were within 3 dB of the predicted values. Thus, it is thought that the computer program can be effectively used in designing noise barriers. Despite intrusive noise periodically overriding the traffic noise from I-495, the latter clearly dominated the neighborhood noise environment.
NASA STI/Recon Technical Report N
- Pub Date:
- July 1982
- Acoustic Velocity;
- Computer Programs;
- Noise Reduction;
- Fluid Mechanics and Heat Transfer