(gentle instrumental music)
- [Narrator] All over the world,
a disturbing sonic phenomenon is plaguing residents
of rural areas, towns,
and even big cities.
This strange sound is a source
of constant menace to those who hear it.
- It's actually something severely impacting people's lives.
It's not just something they hear.
It's something that they feel,
that they detect throughout their body.
- [Narrator] These perpetual low frequency drones
are often simply called the hum.
(gentle instrumental music)
1991 in Taos, New Mexico,
some residents begin to complain to city officials
about an eerie tone haunting them at night.
It wasn't long before the media picked up on the story.
- So I just woke up in the middle of the night
and heard this strong humming sound,
kind of low, kind of like a (mumbling).
- A lot of people who hear the hum,
they refer to it as a bunch of trucks idling nearby.
It's this low level, low frequency, bass kind of sound.
- [Narrator] It's not something that affects everybody.
In a survey of Taos residents,
about 2% of the population claimed to hear it,
but to those few who can,
the hum is more than just an annoyance.
- People say that the hum causes physical symptoms,
sleeplessness, nausea,
and it makes them nervous, and anxious, and depressed,
and the U.S. government actually tried to verify it.
They went to Taos with low frequency sound
detecting equipment,
and they heard nothing.
- [Narrator] If this unnerving hum wasn't coming
from an external source,
maybe the sound originated in the hearers themselves.
- Maybe this is tinnitus.
Tinnitus is a condition where people
constantly hear a ringing in their ears,
and the reason is there might have been some sort of damage,
and so to compensate,
the brain sort of turns up its
quote, unquote, listening mechanism.
But this is probably not tinnitus,
and the reason is tinnitus tends to be a very high signal,
a very high constant whine.
This is more like bass than like treble.
- [Man] Some people can hear it.
Some people can't,
and I live off in the middle of nowhere,
and I listen for it, but I've never heard it.
- [Narrator] Mysteriously,
almost as quickly as the hum began,
it disappeared,
(birds chirping)
leaving residents and officials no closer to an answer,
but the phenomena of unexplained hums
has appeared all over the world,
this time just over the Canadian border
in the city of Windsor, Ontario.
In 2012, more than 22,000 Canadians dialed in
to a local teleconference to complain
about their very own mysterious hum.
- The hum quite frankly was hurting quality
of life here in the city of Windsor.
- So they got researchers
from the University of Windsor to come and take a look,
and they pointed to Zug Island.
(dramatic instrumental music)
It's just this little island
in the Detroit River where there's a lot
of industrial activity,
so they said that there are blast furnaces
by a U.S. steel plant on Zug Island
that are making a lot of sound,
and that's what everybody is hearing.
- [Narrator] But there was one problem.
Zug Island was on U.S. soil.
Without cooperation from the U.S. government,
university researchers were unable
to conduct any tests on the actual island,
and their study was left incomplete.
Reports of new and different hums
were popping up across the globe,
Scotland, Auckland,
Kokomo, Indiana, and elsewhere,
(metal creaking)
and each new case seemed to invite a new theory.
Some experts attributed the hum to electricity pylons.
Other people insisted it was UFOs,
and many believed it was just mass hysteria.
- There's some theories that the hum,
whatever it might be,
is still amplified psychologically.
It's possible that a lot of the people
reporting hearing the hum are reporting it
because they live somewhere
where other people are reporting it.
- [Narrator] Over the years, for every individual hum,
scientists have proposed all manner of explanations
for these distressing sound reverberations.
In Seattle, Washington,
scientists thought it could be armies of mating fish.
The Plainfin Midshipman fish
(fish humming)
use acoustic communication
to attract a mate.
On summer nights, the males contract the muscles
around their gas filled swim bladders.
This whirring oscillation produces a monotone droning sound
calling all nearby females to his nest.
The mating calls' low frequency,
long wavelength allows it to reverberate off the boats,
and also off the shallow parts of the sea floor,
amplifying the sound on land.
A popular conspiracy theory puts forward
that HAARP in Gakona, Alaska,
the High Frequency Active Auroral Research Program,
is responsible for the hum all over the world.
HAARP is made up of 180 antennas
which transmit high power radio frequencies
into an outer layer of the earth's atmosphere.
The theory is that these intense frequency blasts
are invading the minds of people
particularly sensitive to them.
Still there has been no unified theory
for this worldwide mystery,
but recently science has made a breakthrough.
- Some first reports of the hum were in Bristol, England,
in the '70s,
and researchers from Oxford came
and were able to point
toward a large industrial fan nearby
and said that that was the source of the hum,
and when the fan was later decommissioned,
the hum went away.
- [Narrator] But then in 2015,
the people of Bristol began hearing another hum,
baffling residents once again.
- [Man] Is it the hum again?
- [Narrator] This time a recent scientific breakthrough
provided a possible explanation.
Scientists discovered that colliding ocean waves,
and waves moving over the seafloor,
are responsible for microseismic activity.
In turn, this constant vibration gives off a hum.
- They confirmed this in 2017
by putting seismic equipment at the bottom
of the Indian Ocean.
What scientists found is a sound
that's basically emitted by the Earth itself.
- [Narrator] The earth's hum is faint.
It was measured at a level 10,000 times
lower than normal hearing capabilities.
(static crackling)
Despite its promise and the amazing revelations
about the earth's hum,
it seems improbable that this would be
the cause for all hums,
but it does launch a new era
in the investigation of the maddening hum.
(gentle instrumental music)
(dramatic instrumental music)