Imagine hearing a diesel engine somewhere outside your house. You check the street, but there is no vehicle. You listen again. The low rumble continues.
Then someone standing beside you says they cannot hear anything.
That unsettling experience resembles accounts of The Hum, a name given to persistent low sounds reported in Australia and elsewhere. For those who notice it, the puzzle can become intensely frustrating: how do you find a sound that other people cannot hear?
Australian reports of The Hum
In January 2024, ABC News examined reports from Sydney residents who described an elusive humming or pulsating noise.
One woman compared her experience with the rumble of machinery. She initially associated it with nearby construction, then became puzzled when the work ended and the sound continued.
The ABC also reported earlier complaints in Sydney’s eastern suburbs, where Waverley Council had sought assistance investigating a mysterious noise.
These accounts establish that people have reported a troubling experience. They do not establish one shared source.
Is everyone hearing the same thing?
The name suggests a single worldwide phenomenon, but similar descriptions can arise from different causes.
A low rumble might originate in the environment, or it might involve the way an individual’s auditory system produces or processes a sound.
That distinction is central to the investigation. Two people describing an “idling engine” may be giving similar words to experiences with different origins.
A useful explanation therefore needs to account for individual cases, rather than assuming every report belongs to one global mystery.
What recent research found
A study published in PLOS One in March 2026 investigated 28 people who reported persistent low-frequency sounds.
Researchers tested whether unusually sensitive hearing or measurable sounds generated by the inner ear could explain their experiences. Neither explanation accounted for most participants.
The authors suggested low-frequency tinnitus as a plausible explanation for many cases, while acknowledging that it was not directly tested in the study. They also did not rule out external sound sources.
Their conclusion pointed towards several possible mechanisms rather than one universal answer.
Why an explanation matters
For a listener, uncertainty can be as frustrating as the sound itself.
If the apparent noise resembles a machine, searching for a machine makes sense. If no machine is found, the experience becomes harder to discuss with someone who hears nothing.
Scientific investigation can help separate those questions. It can take a person’s experience seriously while examining whether its source is environmental, auditory or still unidentified.
A mystery becoming more understandable
The Hum is an example of how a mystery can change as evidence develops.
Some reports may eventually receive practical explanations. Others may remain unresolved because the necessary measurements were never made.
The interesting question is no longer simply, “What is making that noise?”
It is also, “Why can one person hear it when someone beside them cannot?”
