The Real World Hum is laser focused on Natural Gas Pipelines and Infrastructure as we believe they are the largest single contributor to the Hum heard around the world. 

Natural Gas Pipelines

North America

Natural Gas Pipeline Compressor Stations and Major Natural Gas Transportation Corridors
https://www.sites.google.com/site/metropolitanforensics/natural-gas-pipeline-compressor-stations-and-major-natural-gas-transportation-corridors

New Zealand - https://www.gasindustry.co.nz/about-the-industry/
Ahuroa Underground Gas Storage Facility - https://www.hydrocarbons-technology.com/projects/ahuroa-underground-gas-storage-facility/
Map of Pipelines in New Zealand - https://theodora.com/pipelines/australia_new_zealand_and_papua_new_guinea_pipelines_map.jpg


Low Frequency Noise generated by Natural Gas Pipelines and Infrastructure

Low Frequency Noise of Gas Turbines - January 1973 - The Journal of the Acoustical Society of America
https://www.researchgate.net/publication/243499606_Low_Frequency_Noise_of_Gas_Turbines?

Low Frequency Noise Emission From a Natural Gas Compressor Station -     May 1987
Authors: Manfred Sieminski , Manfred Schneider
https://www.researchgate.net/publication/255047951_Low_Frequency_Noise_Emission_From_a_Natural_Gas_Compressor_Station