The military is currently developing models for calculating scattering in urban sound propagation:
“Future US Army ground sensors in urban terrain will process acoustic signals to detect, classify, and locate sources of interest. Optimal processing will require understanding of the effects of the urban infrastructure on sound propagation. These include multi-path phenomena that will complicate sensing, and must be accounted for in sensor placement and performance algorithms. The objective of this work is to develop spatial processing techniques for acoustic wave propagation data from three-dimensional high-performance computations to quantify scattering due to urban structures and develop reduced-order models of wave-field data.”
and from a second paper:
“The United States Army is continuously improving upon its situational awareness in operational environments. This is particularly difficult in an urban scene because line of sight is limited and because the acoustic interaction between and over the top of the buildings is not yet fully understood. Once this is fully understood the acoustic detection, classification, and localization can be accomplished through the use of well-placed acoustic sensors.”
Ketcham, S., D. K. Wilson, H. Cudney, and M. Parker. 2007. Spatial Processing of Urban Acoustic Wave Fields from High-Performance Computations. In Proceedings of the 2007 DoD High Performance Computing Modernization Program Users Group Conference, 289-295. IEEE Computer Society.
Parker, M., S. Ketcham, and H. Cudney. 2007. Acoustic Wave Propagation in Urban Environments. In Proceedings of the 2007 DoD High Performance Computing Modernization Program Users Group Conference, 233-237. IEEE Computer Society.
Beyond decibels
Trevor Cox in the New Scientist:
“One problem with decibel measurement is that it does not differentiate between “negative” and “positive” sounds. Take the sounds made by a fountain in a town square, happy children in a playground or the cheerful toot of the Manchester tram – any one of which might exceed permitted sound levels. Increasingly, researchers have been pressing for these positive sounds to be considered within urban design alongside more traditional noise-control approaches.”
New Scientist article