As industrial technology advances, man-made noise has increasingly contributed to natural soundscapes. To predict how anthropogenic noise can affect natural environments, engineers build acoustic models over a given terrain; however, many current models are not compatible with common Geographic Information System (GIS) software and become outdated due to software version updates, or are written as proprietary packages unavailable to park management. The goal of this study was to create a true open source outdoor sound propagation model compatible with (but not dependent on) outside GIS software. The model was developed using algorithms from ISO 9613-2, an international standard for attenuation of sound during propagation outdoors. The standard accounts for uneven terrain, atmospheric absorption, screening, wind effects, and ground effects; however, the scope of this thesis is limited to the initial three attenuation factors. Geometric and atmospheric attenuation were directly translatable to a three-dimensional terrain. Additional software was developed in order to translate the two-dimensional screening algorithms for simple terrains to three-dimensional complex terrains. Given sound source inputs and locations over an input Digital Elevation Map, GIS compatible file types of spatially explicit sound pressure level predictions were produced by this model. The model was tested using simple simulated terrains of known ISO 9613-2 cases: one barrier and two barriers. Additionally, the model produced preliminary results using real terrain data and natural gas compressor noise as the sound source. Sound maps were displayed over satellite imagery of the sound pressure level data, and a correlation of visitor acceptability to the sound. The results produced by this work demonstrate a preliminary version of an open-source outdoor sound predictive tool with the capability of mapping visitor experience.