Meteorological influence on sound propagation between adjacent city canyons: A real-life experiment

Abstract

Sound propagation between a courtyard and an adjacent street canyon, as influenced by a wide range of meteorological conditions, was investigated by means of a real-life experiment in a dense urban setting. During several months, test signals were emitted on a regular base by an outdoor loudspeaker in the courtyard and recorded by wall-mounted microphones in the courtyard and the street canyon. Detailed meteorological observations were made at nearby buildings with sensors at roof level. A thorough quality check of the recorded signals was performed, given the large amount of shielding and the presence of background noise. With increasing wind speed and sound frequency, a strong increase in coherence loss was observed. The wide variety of measured vertical temperature lapses was shown to have no effect given the short propagation distance. With increasing downwind wind speed, refraction into the shielded canyon was observed to a limited degree only. The rather small effect of building-induced refraction of sound by wind could be qualitatively explained by the geometry of the city canyons under study.

Influence of rainfall on the noise shielding by a green roof

“…In a final step, the difference in sound pressure level between M1 and M2 yielded the attenuation spectrum for a specific hour. A similar signal processing procedure was employed successfully in a noisy, highly shielded outdoor environment [28].…”

“…At sound frequencies above 1 kHz, the attenuation was found to increase with wind speed (not shown), independent of the wind direction. The main reason for the latter is the loss of coherence, leading to virtually higher attenuations when averaging cross-correlations of the different repetitions at a specific hour [28]. The latter adds to the variability in the measured attenuations.…”

Three-dimensional urban acoustic simulations and scale-model measurements over real-life topography

“…The main problems with real-life measurements are that a live urban area contains too many uncontrollable background noise sources and that sound propagation is affected by complex meteorological conditions. 4 In contrast, a scale-model experiment allows precise control over the source and propagation conditions.…”

Urban Background Noise Mapping: The General Model

“…By comparing with an in-situ long-term measurements [20] and FDTD simulations, it was found that using the ISO standard to calculate A bar underestimates the attenuation considerably. Therefore, a more accurate but still computational efficient approximation is needed.…”