The Taos Hum: The Sound Only Some People Hear (early 1990s)

ARCHIVE FILE · Event year: early 1990s. The investigation took place in 1993 and its findings were published in 1995. This is not breaking news. It’s part of the Redacted Weekly evergreen archive.

Imagine hearing a low, droning hum everywhere you go at home, and the person next to you hears nothing. In the early 1990s, enough residents of the Taos area in northern New Mexico described this experience that, in 1993, they got the attention of their congressional delegation. A team of scientists was sent to find the source.

CASE FILE · RW-ARC-UNX-002
Subject: Persistent low-frequency hum heard by a minority of residents
When: Complaints in the early 1990s; investigation in 1993
Where: Taos and surrounding area, New Mexico
Investigators: About a dozen researchers from UNM, Los Alamos, Sandia and Phillips Laboratory
Evidence: Hearer tone-matching, a resident survey, and geophone and magnetometer readings
Status: Unresolved
Most significant seismic event detected: A gopher

The investigation

The team’s findings were written up by the University of New Mexico’s Joe Mullins and James Kelly, and the team included researchers from Los Alamos National Laboratory, Sandia National Laboratories and the Phillips Air Force Laboratory. Their account appeared in the Acoustical Society of America’s newsletter Echoes (Autumn 1995).

They asked hearers to match what they heard against generated tones. Ten hearers did so, placing the hum at 32 to 80 Hz, modulated at 0.5 to 2 Hz. That’s a low rumble with a slow pulse, and each hearer placed it somewhat differently.

They then looked for a physical source with geophones and magnetometers. They found nothing unusual. The team reported that one apparent seismic “event” turned out to be a gopher. They also checked the frequencies of the U.S. Navy’s extremely low frequency (ELF) transmitters, a popular suspect, and found nothing above background noise.

The survey

The team surveyed residents. About 8,000 questionnaires went out and 1,440 came back. Of those, 161 respondents were classified as hearers. Wikipedia’s summary says the study suggested at least 2% of the population could hear it.

The authors’ conclusion was candid: “we are left with a mystery.”

Who hears it

Wikipedia’s summary of the Taos study and earlier British work describes a fairly consistent pattern:

• Men and women hear it in roughly equal numbers.
• Middle-aged people seem more likely to hear it.
• Some hearers said they could get away from it by traveling. One Taos hearer said it carried for about 30 miles (48 km).
• An earlier 1973 report described a university study of fifty people who complained of a “low throbbing background noise” that others couldn’t hear. In that study the sound peaked between 30 and 40 Hz, was heard only in cool weather with a light breeze and often early in the morning, and was usually confined to an area about 10 km (6 mi) wide.

Taos isn’t the only place with a hum. Reports come from the UK, Canada, Australia, New Zealand, Germany and across the U.S. Most of them are local and named after the town, like the Taos Hum, the Windsor Hum and the Auckland Hum.

Hums that were solved

Taos stays a mystery, but several other hums have been traced to ordinary machinery. Wikipedia lists these:

• West Seattle: traced to a vacuum pump that CalPortland used to unload cargo from ships. Reports stopped after the company replaced the machine’s silencers.
• Windsor, Ontario (from 2011): a roughly 35 Hz hum blamed on a U.S. Steel plant on Zug Island near Detroit. Reports stopped after the plant shut down in April 2020.
• Wellington, NZ: thought to be a visiting ship’s diesel generator.
• Darmstadt, Germany (2021–22): investigators found several sources, including two faulty air conditioners, a faulty heat pump and noise-protection structures at energy plants.
• Kokomo, Indiana: two industrial tones were found, a 36 Hz cooling tower and a 10 Hz air-compressor intake. Some reports continued after both were fixed, so a solved source doesn’t always end the complaints.

Other proposed causes (labeled as proposals)

• Gas pipelines: Engineer Steve Kohlhase, who investigated hums independently, said every location he studied was on or near a high-pressure gas pipeline. This is his hypothesis, not a demonstrated cause.
• Military radio (TACAMO): David Deming has speculated that the very-low-frequency radio used by Navy aircraft to communicate with submarines might be involved. He notes there have been no hum reports around the Navy’s fixed transmitters in Cutler, Maine, and Jim Creek, Washington. This is unproven.
• Over-attention to background noise: In 2009, David Baguley, head of audiology at Addenbrooke’s Hospital in Cambridge, estimated that about one-third of hum complaints have a physical source and the other two-thirds come from people fixating on ordinary background sound. He also said most cases remain unexplained.

Hearers disagree about whether the sound is worse indoors or outdoors. Some say double glazing makes it worse, because it blocks other noise and leaves the hum more noticeable.

Grades