Why Deep Hums Feel So Uncanny

Introduction

Many reports of mysterious “UFO noises” do not describe a sharp sound at all. Instead, witnesses often mention a deep hum, a distant rumble, a vibrating drone or something that feels more like pressure than a recognisable engine. One reason these reports can seem so strange is that low-frequency sound behaves differently from higher-pitched noise. Deep sounds lose energy more slowly, bend around obstacles more easily and can be guided by atmospheric conditions over surprisingly long distances. A factory, motorway, freight train or aircraft may therefore sound much larger, closer or more overhead than it really is. In some conditions, listeners can hear the low-frequency component of a sound source while the higher-frequency clues that would normally identify it have faded away. [Acoustics Today]acousticstoday.orgAcoustics Todaysound Propagation in the Atmospheric boundary layerSound propagation in the atmosphere impacts noise emissions from factories and highways, detection and location of sound sources…Read… [odeon]odeon.dkODEON Room Acoustics SoftwareAir Attenuation in Octave Bands and How to Normalize…by JH Rindel · 2024 · Cited by 5 — The attenuation i… Within discussions of unusual sky sounds, this mechanism is important because it explains why many reports focus on an unsettling vibration or hum rather than a clear mechanical signature. What remains audible is often the part of the sound most difficult for the human brain to locate. Ascent [HowStuffWorks]science.howstuffworks.comHow Stuff Works How the Hum WorksHowStuffWorksHow the Hum Works - Science | HowStuffWorksHum sufferers describe a low-frequency buzz accompanied by a rumbling vibration…

Why Low Frequencies Travel So Well

Sound does not attenuate equally across all frequencies. High-frequency sounds are absorbed by the atmosphere more readily than low-frequency sounds. As distance increases, the sharper elements of a noise source tend to fade first, while the deeper components survive longer. That is why distant traffic often sounds like a broad roar rather than individual engines, and why a faraway industrial plant may be heard as a low drone rather than a collection of mechanical noises. ODEON Room Acoustics Software [Physics Stack Exchange]physics.stackexchange.comdo low frequency sounds really carry longer distancesPhysics Stack ExchangeDo low frequency sounds really carry longer distances?Nov 24, 2013 — Do low frequencies carry farther than high fre…

Low-frequency waves also have very long wavelengths. Because of this, they diffract, or bend, around hills, buildings and other obstacles more effectively than higher frequencies. A listener may therefore hear a deep rumble even when the source is hidden behind terrain or structures that would block more directional sounds. [Commercial Acoustics®]commercial-acoustics.comHigh frequencies are more directional and less prone to bending.Read moreCommercial Acoustics®How Sound Travels: The Science of Sound Waves!Dec 11, 2020 — Low-frequency waves diffract more easily, making them m…

Atmospheric conditions can strengthen the effect further. During temperature inversions and certain wind conditions, sound waves refract back toward the ground rather than dispersing upward. Environmental acoustics researchers have documented how these conditions can increase the distance over which transportation and industrial noise remains audible. What reaches the listener is often dominated by the lowest frequencies because those frequencies have already travelled most efficiently through the atmosphere. [Acoustics Today]acousticstoday.orgAcoustics Todaysound Propagation in the Atmospheric boundary layerSound propagation in the atmosphere impacts noise emissions from factories and highways, detection and location of sound sources…Read… [Soft dB]softdb.comSoft d BThe Effect of Wind and Temperature Gradients on SoundThe Effect of Wind and Temperature Gradients on Sound…May 14, 2019 — The wind can slow down or accelerate the speed of sound, dependin…Published: May 14, 2019

This combination creates a familiar pattern in unusual-noise reports: the sound feels powerful, but its origin seems impossible to identify.

Why Deep Sounds Are Hard to Identify

Humans are relatively poor at locating low-frequency sound sources. The auditory system relies heavily on timing differences and intensity differences between the ears, but very long wavelengths make these directional cues less precise. The result is that a deep hum may seem to come from everywhere at once or from no obvious direction at all. [Ascent]ascent.aeroProject 1 | Low Frequency Noise StudyIt encompassed many factors, including the source level and its…Read more…

Another problem is spectral filtering. As sound travels, higher frequencies are stripped away more quickly than lower ones. Imagine hearing only the bass component of a machine while losing the rattles, clicks and tonal details that normally reveal its identity. The remaining sound can feel detached from its source. A distant quarry, industrial compressor or aircraft may no longer sound like machinery in the ordinary sense; it becomes a vague atmospheric presence. ODEON Room Acoustics Software [Physics Stack Exchange]physics.stackexchange.comdo low frequency sounds really carry longer distancesPhysics Stack ExchangeDo low frequency sounds really carry longer distances?Nov 24, 2013 — Do low frequencies carry farther than high fre…

People also perceive low-frequency sound differently from mid-range sound. Some describe it as a vibration in walls, floors or the chest rather than as a conventional noise. Studies of low-frequency aircraft noise and environmental hums note that annoyance is often linked not only to audibility but also to vibration, rattling and a sensation of pressure. [Ascent]ascent.aeroAscent22 Oct 2019 — Use subtraction method to minimize source uncertainties. 3. Use sound exposure level (top 10 dB exposure level) to an… [ScienceDirect]sciencedirect.comAir–ground interaction in long range propagation of low…by C Madshus · 2005 · Cited by 47 — This paper focuses on the interaction betw…

This helps explain why witnesses sometimes insist they heard something extraordinary even when no dramatic sound level was measured. The experience can feel physically intrusive despite being acoustically subtle.

When a Sound Seems to Come From the Sky

A common feature of “sky hum” reports is the impression that the sound is overhead. This can happen even when the source is on the ground.

Under favourable atmospheric conditions, refracted sound can return toward the surface after travelling through layers of air with different temperatures and wind speeds. Instead of seeming to radiate from a distant industrial site or transport corridor, the sound field can become diffuse and difficult to trace. Listeners may perceive the noise as descending from above or hovering in the environment. [Acoustics Today]acousticstoday.orgAcoustics Todaysound Propagation in the Atmospheric boundary layerSound propagation in the atmosphere impacts noise emissions from factories and highways, detection and location of sound sources…Read… [Soft dB]softdb.comSoft d BThe Effect of Wind and Temperature Gradients on SoundThe Effect of Wind and Temperature Gradients on Sound…May 14, 2019 — The wind can slow down or accelerate the speed of sound, dependin…Published: May 14, 2019

Researchers studying outdoor acoustics have long observed that weather conditions can dramatically alter perceived source location and loudness. Aircraft-noise modelling, for example, must account for atmospheric propagation because identical aircraft can sound very different depending on temperature gradients and wind structure. MDPI [HMMH]hmmh.comHMMHWeather Effects on the Propagation of Aircraft Noise | HMMHincrease in aircraft noise in the 360 Community and, if feasible, make noise…

For someone hearing a low-frequency rumble at night, the effect can be particularly misleading. The visual environment is quiet, the source may be kilometres away and the sound lacks the higher-frequency details that would normally identify it. What remains is an apparently source-less vibration occupying a large area.

Machinery, Traffic and Aircraft as Hidden Sources

Several ordinary sources produce strong low-frequency energy capable of travelling long distances under favourable conditions.

Heavy industry and infrastructure

Large fans, compressors, power-generation equipment, pumping stations and industrial facilities often emit persistent low-frequency noise. Because these frequencies attenuate slowly, the sound may be heard well beyond the facility itself, especially during nighttime inversions. [Historic Ipswich]historicipswich.netHistoric Ipswich The “Hum”Historic IpswichThe “Hum” - Historic IpswichLow-frequency noise has low attenuation, so it can reach distant locations. The temperature i…

Road traffic

Motorways generate a continuous low-frequency background from engines, tyres and aerodynamic turbulence. At long range, individual vehicles disappear acoustically and merge into a broad rumbling band that can resemble distant machinery or an approaching storm. [Acoustics Today]acousticstoday.orgAcoustics Todaysound Propagation in the Atmospheric boundary layerSound propagation in the atmosphere impacts noise emissions from factories and highways, detection and location of sound sources…Read…

Freight trains

Long trains produce powerful low-frequency components through engine operation, wheel-rail interaction and vibration of large structures. Depending on terrain and weather, the sound can travel far beyond what listeners expect from a rail line. [AIP Publishing]pubs.aip.org31 1 onlineAIP PublishingTutorial on sound propagation outdoorsby TFW Embleton · 1996 · Cited by 509 — Techniques for measuring the acoustic impedan…

[Aircraft]sciencedirect.comAircraft noise impact prediction with incorporation of…by C Wu · 2023 · Cited by 19 — As part of a research effort towards greener avi…

Aircraft generate substantial low-frequency noise, particularly during certain phases of flight. Researchers studying community noise around airports have repeatedly found that atmospheric conditions influence how aircraft sound propagates and how strongly it is perceived on the ground. A listener may hear a distant aircraft as a lingering hum or vibration without immediately recognising it as aviation noise. Ascent [Federal Aviation Administration]faa.govaircraft noiseFederal Aviation AdministrationAircraft Noise31 Jan 2025 — Aircraft and airport noise are complex issues that have been studied for decad…

These sources are not always loud in an absolute sense. Their significance lies in the way low-frequency energy survives long-distance propagation while more identifiable frequencies fade.

The Link to Persistent Hum Reports

The so-called “Hum” phenomenon reported in various countries illustrates how difficult low-frequency sound can be to interpret. People who report hearing persistent hums commonly compare them to distant diesel engines, generators or industrial machinery. The sound is often described as being most noticeable at night, when background noise decreases and atmospheric conditions can favour long-range propagation. [HowStuffWorks]science.howstuffworks.comHow Stuff Works How the Hum WorksHowStuffWorksHow the Hum Works - Science | HowStuffWorksHum sufferers describe a low-frequency buzz accompanied by a rumbling vibration… [Historic Ipswich]historicipswich.netHistoric Ipswich The “Hum”Historic IpswichThe “Hum” - Historic IpswichLow-frequency noise has low attenuation, so it can reach distant locations. The temperature i…

Not every reported hum has been conclusively explained, and some cases remain disputed. However, environmental acoustics investigations frequently focus on low-frequency industrial, transportation or infrastructure sources because those sounds possess exactly the characteristics that make identification difficult: long travel distances, weak directionality and a tendency to be felt as much as heard. [Historic Ipswich]historicipswich.netHistoric Ipswich The “Hum”Historic IpswichThe “Hum” - Historic IpswichLow-frequency noise has low attenuation, so it can reach distant locations. The temperature i… [Exxos Forum]exxosforum.co.ukTurbulence within these pipelines can create pressureExxos ForumThe Global Low-Frequency Hum: Causes and Theories - Exxos ForumOne plausible explanation for the hum is the low-frequency soun…

In the context of UFO-noise reports, this does not mean every unusual sound has a single mundane explanation. It does show why deep, vibrating noises occupy such a prominent place in witness accounts. Low-frequency sound is unusually good at surviving the journey from a distant source to a listener while shedding the clues that would reveal where it came from. The result can be a powerful impression of a mysterious object overhead when the actual source is far away, hidden or acoustically transformed by the atmosphere. [Acoustics Today]acousticstoday.orgAcoustics Todaysound Propagation in the Atmospheric boundary layerSound propagation in the atmosphere impacts noise emissions from factories and highways, detection and location of sound sources…Read… [2Commercial Acoustics®]commercial-acoustics.comHigh frequencies are more directional and less prone to bending.Read moreCommercial Acoustics®How Sound Travels: The Science of Sound Waves!Dec 11, 2020 — Low-frequency waves diffract more easily, making them m…

Amazon book picks

Further Reading

Books and field guides related to Why Deep Hums Feel So Uncanny. Use these as the next step if you want deeper reading beyond the article.

Book

The Soundscape

By R. Murray Schafer

Explains environmental and low-frequency sound perception.

See on Amazon

Book

Weather For Dummies

By John D. Cox

Explains conditions that allow deep sounds to travel unusually far.

See on Amazon

Book

The Great Animal Orchestra

By Bernie Krause

Helps readers understand how low sounds dominate distant listening environments.

See on Amazon

Book

The UFO Experience

By J. Allen Hynek

Places mysterious hum reports within broader UFO investigation history.

See on Amazon

Browse more on Amazon: The Soundscape Weather For Dummies The Great Animal Orchestra

As an Amazon Associate I earn from qualifying purchases.

Endnotes

1. Source: odeon.dk
   Link: https://odeon.dk/pdf/A32-applsci-14-10139_Rindel.pdf
   Source snippet

   ODEON Room Acoustics SoftwareAir Attenuation in Octave Bands and How to Normalize...by JH Rindel · 2024 · Cited by 5 — The attenuation i...

2. Source: commercial-acoustics.com
   Title: High frequencies are more directional and less prone to bending.Read more
   Link: https://commercial-acoustics.com/sound-advice/how-sound-travels/
   Source snippet

   Commercial Acoustics®How Sound Travels: The Science of Sound Waves!Dec 11, 2020 — Low-frequency waves diffract more easily, making them m...

3. Source: ascent.aero
   Title: Project 1 | Low Frequency Noise Study
   Link: https://ascent.aero/partner-1/
   Source snippet

   It encompassed many factors, including the source level and its...Read more...

4. Source: science.howstuffworks.com
   Title: How Stuff Works How the Hum Works
   Link: https://science.howstuffworks.com/science-vs-myth/unexplained-phenomena/the-hum.htm
   Source snippet

   HowStuffWorksHow the Hum Works - Science | HowStuffWorksHum sufferers describe a low-frequency buzz accompanied by a rumbling vibration...

5. Source: pubs.aip.org
   Title: 31 1 online
   Link: https://pubs.aip.org/asa/jasa/article-pdf/100/1/31/11401662/31_1_online.pdf
   Source snippet

   AIP PublishingTutorial on sound propagation outdoorsby TFW Embleton · 1996 · Cited by 509 — Techniques for measuring the acoustic impedan...

6. Source: sciencedirect.com
   Link: https://www.sciencedirect.com/science/article/abs/pii/S0003682X04001598
   Source snippet

   Air–ground interaction in long range propagation of low...by C Madshus · 2005 · Cited by 47 — This paper focuses on the interaction betw...

7. Source: mdpi.com
   Link: https://www.mdpi.com/2073-4433/12/11/1424
   Source snippet

   MDPISound Propagation Modelling for Manned and Unmanned...by R Kapoor · 2021 · Cited by 50 — A more reliable and accurate modelling of n...

8. Source: hmmh.com
   Link: https://hmmh.com/wp-content/uploads/2019/08/NOISECON2019_Czech_WxEffects.pdf
   Source snippet

   HMMHWeather Effects on the Propagation of Aircraft Noise | HMMHincrease in aircraft noise in the 360 Community and, if feasible, make noise...

9. Source: facebook.com
   Link: https://www.facebook.com/groups/anythingaycliffe/posts/1641179699350667/
   Source snippet

   So apparently, this hum that everyone can hear is a natural global...September 28, 2019 — It is almost universally described as the soun...

   Published: September 28, 2019

10. Source: sciencedirect.com
    Link: https://www.sciencedirect.com/science/article/pii/S2949736125000491
    Source snippet

    Transmission, attenuation, resonance and health implicationsby Y Takefuji · 2025 — This paper examines noise attenuation in relation to s...

11. Source: sciencedirect.com
    Link: https://www.sciencedirect.com/science/article/abs/pii/S1874490726000066
    Source snippet

    A two-stage acoustic source localization algorithm...by TT Tai · 2026 — This paper presents a novel two-stage acoustic source localizati...

12. Source: sciencedirect.com
    Link: https://www.sciencedirect.com/science/article/abs/pii/S1361920921003096
    Source snippet

    The aviation noise complaint effect on home pricesby FL Friedt · 2021 · Cited by 24 — This noise pollution effect, persists for roughly 1...

13. Source: sciencedirect.com
    Link: https://www.sciencedirect.com/science/article/abs/pii/S0003682X12001272
    Source snippet

    Low-frequency sound propagation in porous media: Glass...by MJ White · 2012 · Cited by 9 — In this paper, we make laboratory measurement...

14. Source: sciencedirect.com
    Link: https://www.sciencedirect.com/science/article/abs/pii/S1361920923003425
    Source snippet

    Aircraft noise impact prediction with incorporation of...by C Wu · 2023 · Cited by 19 — As part of a research effort towards greener avi...

15. Source: sciencedirect.com
    Link: https://www.sciencedirect.com/science/article/pii/S0301479723019898
    Source snippet

    Using aircraft tracking data to estimate the geographic...by DH Betchkal · 2023 · Cited by 9 — This article addresses the ongoing need t...

16. Source: mdpi.com
    Link: https://www.mdpi.com/2226-4310/12/10/930
    Source snippet

    Aircraft Noise Assessment Using Noise Points: Conception...by J Blinstrub · 2025 — The noise point concept is verified at various airpor...

17. Source: ascent.aero
    Link: https://ascent.aero/documents/2019/10/october-2019-ascent-040.pdf
    Source snippet

    Ascent22 Oct 2019 — Use subtraction method to minimize source uncertainties. 3. Use sound exposure level (top 10 dB exposure level) to an...

18. Source: pubs.aip.org
    Title: Low frequency non reciprocal sound propagation
    Link: https://pubs.aip.org/asa/jasa/article/156/1/314/3303097/Low-frequency-non-reciprocal-sound-propagation
    Source snippet

    aip.orgLow-frequency non-reciprocal sound propagation features...11 Jul 2024 — This work demonstrates that by adjusting the pore geometr...

19. Source: youtube.com
    Title: Sound waves
    Link: https://www.youtube.com/watch?v=lwOkEXbwu90
    Source snippet

    4 What REALLY Happens to Sound Waves in a Vacuum?...

20. Source: acousticstoday.org
    Title: Acoustics Todaysound Propagation in the Atmospheric boundary layer
    Link: https://acousticstoday.org/wp-content/uploads/2015/06/Sound-Propagation-in-the-Atmospheric-Boundary-Layer-D.-Keith-Wilson-Chris-L.-Pettit-and-Vladimir-E.-Ostashev.pdf
    Source snippet

    Sound propagation in the atmosphere impacts noise emissions from factories and highways, detection and location of sound sources...Read...

21. Source: historicipswich.net
    Title: Historic Ipswich The “Hum”
    Link: https://historicipswich.net/2024/12/02/the-hum/
    Source snippet

    Historic IpswichThe “Hum” - Historic IpswichLow-frequency noise has low attenuation, so it can reach distant locations. The temperature i...

22. Source: physics.stackexchange.com
    Title: do low frequency sounds really carry longer distances
    Link: https://physics.stackexchange.com/questions/87751/do-low-frequency-sounds-really-carry-longer-distances
    Source snippet

    Physics Stack ExchangeDo low frequency sounds really carry longer distances?Nov 24, 2013 — Do low frequencies carry farther than high fre...

23. Source: softdb.com
    Title: Soft d BThe Effect of Wind and Temperature Gradients on Sound
    Link: https://www.softdb.com/blog/effect-of-wind-and-temperature-gradients-on-sound-waves/
    Source snippet

    The Effect of Wind and Temperature Gradients on Sound...May 14, 2019 — The wind can slow down or accelerate the speed of sound, dependin...

    Published: May 14, 2019

24. Source: faa.gov
    Title: aircraft noise
    Link: https://www.faa.gov/noise/aircraft_noise
    Source snippet

    Federal Aviation AdministrationAircraft Noise31 Jan 2025 — Aircraft and airport noise are complex issues that have been studied for decad...

25. Source: exxosforum.co.uk
    Title: Turbulence within these [pipelines]({{ ‘pipelines/’ | relative_url }}) can create pressure
    Link: https://www.exxosforum.co.uk/articles/hum.html
    Source snippet

    Exxos ForumThe Global Low-Frequency Hum: Causes and Theories - Exxos ForumOne plausible explanation for the hum is the low-frequency soun...

26. Source: faa.gov
    Link: https://www.faa.gov/noise/levels
    Source snippet

    Aircraft Noise Levels & Stages22 Jul 2022 — The FAA regulates the maximum noise level that an individual civil aircraft can emit through...

27. Source: acousticstoday.org
    Link: https://acousticstoday.org/predicting-sound-propagation-in-the-atmosphere/

28. Source: youtube.com
    Title: Aircraft Noise 101
    Link: https://www.youtube.com/watch?v=BA207LUT-wE
    Source snippet

    Introduction to Noise Science and ModelingThe Department of the Navy uses noise modeling to analyze community noise exposure around its a...

29. Source: britannica.com
    Link: https://www.britannica.com/science/sound-physics/Sound-absorption
    Source snippet

    Frequency, Wavelength, AbsorptionThis means that the lower frequencies of a voice bend around a corner more readily than the higher frequ...

30. Source: nonoise.org
    Link: https://www.nonoise.org/epa%20index/roll17/roll17doc7.pdf
    Source snippet

    AIRCRAFT OVERFLIGHT STUDY Effect of Aircraft Altitude...Due to "atmospheric absorption," sound levels decrease with slant distance an ad...

Additional References

1. Source: r2sonic.com
   Link: https://www.r2sonic.com/wp-content/uploads/2020/03/Basic-Acoustic-Theory.pdf
   Source snippet

   Basic Acoustic TheoryAbsorption is frequency dependent and refers to the conversion of acoustic energy to heat when it strikes chemically...

2. Source: dael.euracoustics.org
   Link: https://dael.euracoustics.org/landing_pages/aaua/65295.html
   Source snippet

   Acustica ELectronicaSo the sound propagation models of common aircraft noise calculation tools, like the German AzBor the Integrated Nois...

3. Source: people.ee.ethz.ch
   Link: https://people.ee.ethz.ch/~isistaff/courses/ak1/acoustics-sound-propagation-outdoors.pdf
   Source snippet

   ETH Zurich PeopleSound propagation outdoors▷ today meteorological effects on sound propagation can be predicted with sophisticated calcul...

4. Source: researchgate.net
   Link: https://www.researchgate.net/publication/230549694_Outdoor_Sound_Propagation
   Source snippet

   Outdoor Sound PropagationThe propagation of the acoustic wave is dependent on meteorological conditions such as relative humidity, wind s...

5. Source: sfu.ca
   Link: https://www.sfu.ca/sonic-studio-webdav/cmns/Handbook5/handbook/Sound_Propagation.html
   Source snippet

   Simon Fraser UniversitySound PropagationThere are several important factors which affect the propagation of sound: geometric spreading, a...

6. Source: sfu.ca
   Link: https://www.sfu.ca/sonic-studio-webdav/handbook/Sound_Propagation.html
   Source snippet

   Sound_PropagationThere are several important factors which affect the propagation of sound: geometric spreading, atmospheric effects, and...

7. Source: reddit.com
   Link: https://www.reddit.com/r/mystery/comments/qshi7b/the_worldwide_hum_the_mysterious_sound_that_up_to/
   Source snippet

   The Worldwide Hum, The Mysterious Sound that up to 2% of People...November 12, 2021 — These hums are very low-frequency noises which hum...

   Published: November 12, 2021

8. Source: resource.npl.co.uk
   Link: https://resource.npl.co.uk/acoustics/techguides/envnoiseassessment/appendix_a.pdf
   Source snippet

   a sound propagation theory & methodologiesThis dependency largely arises from the increasing velocity gradients experienced by the oscill...

9. Source: zhihu.com
   Link: https://www.zhihu.com/en/answer/99131739
   Source snippet

   So, as you move farther from the sound source, the high frequencies become more muted. This is also why low frequencies can travel long d...

10. Source: reddit.com
    Title: These noises are referred to as flutter and hum. What is
    Link: https://www.reddit.com/r/TheHum/comments/1ascin1/the_hum_explained_by_an_industry_service_provider/
    Source snippet

    The Hum explained by an industry service provider: r/TheHumFebruary 17, 2024 — They occur due to the transmission of high pressure natur...

    Published: February 17, 2024