Auralization of Vertical Take-Off and Landing (VTOL) in Urban Environments

The topic defines the problem as the development and demonstration of computationally efficient tools capable of modeling sound propagation in an urban environment for creating auralizations of UAM vehicles. The tools would be suitable for eventual integration with the NASA Auralization Framework (NAF).The topic requires a set of modules to be delivered which will integrate with existing NAF infrastructure to efficiently find acoustic propagation paths in a complicated modeled urban environment and deliver them to the path traverser module. Delivered modules will include a pathfinder module, a source module, and a terrain module.The pathfinder module will need to be capable of finding paths which represent all relevant physical acoustic wave propagation phenomena in the environment. The primary acoustic phenomena to be addressed within the pathfinder module are specular reflection and diffusion, with the ability to add atmospheric refraction in the future.In addition to a pathfinder module, a method of integrating directional source radiation will be provided. The source model will be fed through a bank of FIR filters arranged spatially, allowing for frequency dependent directional radiation. Otherwise, the source model could be computed in the frequency domain, by computing the spectrum of each direction, applying to the spectrum of the source, and then generating the source audio via an inverse Fourier transform. Relevant benefits and detriments of each material will be reported on during the phase I effort.An improved terrain model will be implemented as well, which allows for the storage of urban-scale complex environments. Work will be done to find high quality sources of data to populate the environments, including sources like the cityGML project.