Some Iowans have heard the ‘World Hum,’ but what is it?

As someone who spent the better part of their early teens and twenties listening to music WAY too loud, I am familiar with the term tinnitus (Archer fans anyone). It's that faint ringing or humming in the ear that comes as soon as it goes. It's annoying, but usually bearable and can be linked to aging and other underlying causes; like listening to Metallica albums way to loud for way to long. But what if I said there was another phenomenon of sorts that has people wondering, what that humming sound right here in Iowa, or even crazier the whole world!

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Some residents across Iowa have reported hearing a steady, low-frequency sound that seems to have no obvious source. It’s often described as a distant diesel engine idling, a deep droning rumble, or a faint mechanical hum that sits just under everyday noise. In many cases, people say it becomes more noticeable at night, especially indoors when everything else is quiet.

World Hum Map Database

According to data collected in the World Hum Map and Database Project, cases have been logged in several Iowa cities: Des Moines, Davenport, Iowa City, and Cedar Rapids. That pattern fits a global trend, with most hum reports coming from urban or suburban areas near larger population centers, rather than remote rural regions.

So what exactly is the “World Hum”?

The World Hum is not considered a single confirmed sound source. Instead, it’s a label used to describe a cluster of similar experiences reported around the world. The World Hum Map project, created by researcher Dr. Glen MacPherson, was designed to collect these reports and look for patterns. MacPherson, a former University of British Columbia educator and researcher, became interested in the phenomenon after experiencing it himself and discovering a larger online community reporting similar symptoms.

On the project site, the Hum is described as an unusual low-frequency perception that some people experience while others in the same location don't hear at all. Researchers involved with the project estimate that a small percentage of the population may experience this under certain conditions. Some studies say around 2% of the popluation.

One of the most debated aspects is why the Hum seems so inconsistent. In some cases, it may be linked to real environmental sources: traffic, industrial equipment, electrical infrastructure, or other low-frequency vibrations that travel long distances and are difficult to pinpoint. The recent and frequent introduction of AI data centers has only created more instances of a "humming interference." In other cases, it may be related to internal auditory processes, like the above-mentioned tinnitus or other neurological hearing effects.

The project also outlines several competing theories, including environmental infrasound, geological activity, electromagnetic interactions, and internal biological mechanisms. However, none of these explanations has been definitively proven, and researchers continue to treat the phenomenon as unresolved. Not to mention that conspiracy theories abound as to what this "hum" might be.

What makes the World Hum so intriguing is not just the sound itself, but the fact that people consistently describe similar experiences across different countries and environments. Stranger still, there are often no measurable noises present at the time. Whether it turns out to be a hidden environmental signal, a sensory processing condition, or a mix of both, the World Hum remains one of those unusual phenomena where perception and measurement don’t always align. For now, it sits somewhere between mystery and science-in-progress. Me? I'll stick with my tinnitus, at least I know what caused it.