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Strange sky sounds, witness reports, acoustic clues, and grounded explanations.

Within UFO Noises

When Ordinary Sounds Come From the Sky

Wind, humidity, and temperature layers can bend ordinary sounds until they seem to come from the sky.

On this page

  • How sound bends outdoors
  • Night conditions and distant noise
  • Why direction can be misleading
Preview for When Ordinary Sounds Come From the Sky

Introduction

Reports of mysterious “UFO noises” often focus on what people hear rather than what they see. A common pattern is a sound that seems to come from the sky even though no visible source is present: distant metallic groans, low-frequency humming, booming noises or engine-like drones. In many cases, the atmosphere itself can help explain why ordinary sounds appear strange. Changes in temperature, wind and humidity alter the way sound travels outdoors, sometimes carrying familiar noises over unexpectedly long distances and bending them into directions that mislead listeners. Rather than creating new sounds, the atmosphere can reshape existing ones until they seem detached from their real source. [Acoustics Today]acousticstoday.orgAcoustics Todaysound Propagation in the Atmospheric boundary layerJune 1, 2015 — by DK Wilson · Cited by 44 — A positive vertical gradient may be caused either by a ground- based temperature inversion, m…Published: June 1, 2015 [acoustics]acoustics.org.nzRefraction of sound is the bending of sound waves caused by propagation through continually varying media or medium conditions54.Read more… This matters because many reports of“sky sounds” occur under conditions known to enhance long-range sound propagation, especially during calm nights, early mornings and periods of temperature inversion. Understanding these acoustic effects does not explain every unusual report, but it helps clarify why factories, traffic, trains, aircraft and other ordinary sources can sometimes seem as though they are hovering overhead. [Acentech]acentech.comAcentechCold Snaps and Sound Waves: Atmospheric AcousticsFeb 15, 2022 — This condition is called a temperature inversion, where the sound… [Wikipedia]WikipediaInversion (meteorologyInversion (meteorology)In meteorology, an inversion (or temperature inversion) is a phenomenon in which a layer of warmer air overlies…

Overview image for Atmosphere

How Sound Bends Outdoors

Most people imagine sound travelling in a straight line. In reality, sound waves are constantly influenced by the atmosphere through a process called refraction. As air conditions change with altitude, the speed of sound changes as well. When one part of a sound wave moves faster than another, the wave bends. [Simon Fraser University]sfu.caSimon Fraser UniversitySound PropagationHigher temperatures produce higher speeds of sound. Since the temperature of the atmosphere is no… [Acoustical Society of New Zealand]acoustics.org.nzRefraction of sound is the bending of sound waves caused by propagation through continually varying media or medium conditions54.Read more…

Under normal daytime conditions, the ground is warmed by the Sun, making the air near the surface warmer than the air above. Because sound travels slightly faster in warmer air, sound waves tend to bend upward. This can make distant noises seem quieter because some of their energy is directed away from listeners at ground level. [Simon Fraser University]sfu.caSimon Fraser UniversitySound PropagationHigher temperatures produce higher speeds of sound. Since the temperature of the atmosphere is no…

The situation reverses during a temperature inversion. In an inversion, cooler air sits near the ground while warmer air remains above it. Instead of bending upward, sound waves curve back toward the surface. The atmosphere effectively acts like a giant acoustic lens, guiding sound over much greater distances than usual. [Acoustics Today]acousticstoday.orgAcoustics Todaysound Propagation in the Atmospheric boundary layerJune 1, 2015 — by DK Wilson · Cited by 44 — A positive vertical gradient may be caused either by a ground- based temperature inversion, m…Published: June 1, 2015 [acentech]acentech.comAcentechCold Snaps and Sound Waves: Atmospheric AcousticsFeb 15, 2022 — This condition is called a temperature inversion, where the sound… Researchers in environmental acoustics and aircraft-noise studies have long documented this effect because it significantly alters how far industrial and transportation noise can travel. Temperature gradients and wind gradients together can refract sound rays, changing where sound energy concentrates and where it fades. [nasa]ntrs.nasa.govTechnical Reports Server Atmospheric Turbulence Effects on ' Aircraft Noise_radients can also be determined if profiles of the mean temperature and wind are known or measured. (…Read more… Technical Reports Server [acoustics]acoustics.org.nzRefraction of sound is the bending of sound waves caused by propagation through continually varying media or medium conditions54.Read more… A listener may therefore hear:

  • Road traffic from several kilometres away.
  • Aircraft noise that seems unusually loud.
  • Industrial machinery carrying across valleys.
  • Train sounds appearing detached from railway lines.
  • Deep droning tones with no obvious nearby source. [The Natural Navigator]naturalnavigator.comsounds during a temperature inversionThe Natural NavigatorSounds during a temperature inversion7 Jan 2019 — Road noise travels much further during a temperature inversion. An… [acentech]acentech.comAcentechCold Snaps and Sound Waves: Atmospheric AcousticsFeb 15, 2022 — This condition is called a temperature inversion, where the sound… Because the listener cannot see the actual source, the sound may be interpreted as originating from the sky itself.

Atmosphere illustration 1

Night Conditions and Distant Noise

Many reports of unexplained outdoor sounds occur after sunset or before sunrise. This timing is significant because nighttime conditions frequently favour long-distance sound transmission.

As the ground cools after dark, the air closest to the surface often becomes colder than the air above, producing a surface-based temperature inversion. During these periods, distant sounds that would normally dissipate can remain trapped within atmospheric layers and travel efficiently across large areas. [Acentech]acentech.comAcentechCold Snaps and Sound Waves: Atmospheric AcousticsFeb 15, 2022 — This condition is called a temperature inversion, where the sound… [The Natural Navigator]naturalnavigator.comsounds during a temperature inversionThe Natural NavigatorSounds during a temperature inversion7 Jan 2019 — Road noise travels much further during a temperature inversion. An…

People often notice this effect in everyday life without realising it. A motorway that is barely audible during the afternoon may become clearly audible late at night. Dogs barking, train horns and industrial equipment can suddenly seem much closer than they really are. Outdoor observers sometimes describe hearing an indistinct mechanical drone that appears to come from nowhere. [The Natural Navigator]naturalnavigator.comsounds during a temperature inversionThe Natural NavigatorSounds during a temperature inversion7 Jan 2019 — Road noise travels much further during a temperature inversion. An…

Humidity and atmospheric stability can further enhance the impression. Calm, stable air reduces turbulence that would otherwise scatter sound energy. The result can be a cleaner, more focused transmission path for low-frequency noise, which is especially effective at travelling long distances. ScienceDirect [De Gruyter Brill]degruyterbrill.comTo study its variations over time and location due to solar…Read more…

This helps explain why some “sky trumpet” recordings and mysterious humming reports emerge during quiet nighttime conditions. The sound may be genuine, but its apparent location and intensity can be heavily influenced by atmospheric structure rather than by an unusual object overhead. [Acoustics Today]acousticstoday.orgAcoustics Todaysound Propagation in the Atmospheric boundary layerJune 1, 2015 — by DK Wilson · Cited by 44 — A positive vertical gradient may be caused either by a ground- based temperature inversion, m…Published: June 1, 2015 [Acentech]acentech.comAcentechCold Snaps and Sound Waves: Atmospheric AcousticsFeb 15, 2022 — This condition is called a temperature inversion, where the sound…

Conceptual Physics: Refraction of Sound

Channel: Marshall Ellenstein · Views: 74.5K · Uploaded: May 2011 · Length: 3 minutes 43 seconds

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Why Direction Can Be Misleading

One of the most confusing aspects of atmospheric acoustics is that listeners are often poor at locating the true origin of unusual sounds.

Humans determine direction partly by comparing the tiny timing and loudness differences between what each ear receives. When sound arrives through a complicated path involving reflections, refraction and scattering, these cues become unreliable. The perceived source may appear displaced from its actual location. [Acoustical Society of New Zealand]acoustics.org.nzRefraction of sound is the bending of sound waves caused by propagation through continually varying media or medium conditions54.Read more…

A distant industrial facility can therefore sound as though it is above the listener rather than on the horizon. Traffic may seem to emerge from open sky. A train horn may appear to move in unexpected directions as atmospheric conditions shift. In some situations, sound waves can even skip over certain areas and concentrate in others, creating “acoustic shadow” zones where people nearby hear little while people farther away hear a great deal. [Thermaxx Jackets]thermaxxjackets.comThermaxx Jackets Refraction of Sound Waves & Acoustic Shadows ExplainedThermaxx JacketsRefraction of Sound Waves & Acoustic Shadows ExplainedMarch 17, 2017 — 17 Mar 2017 — In this article we are going to expl…Published: March 17, 2017 [Acoustics]acoustics.org.nzRefraction of sound is the bending of sound waves caused by propagation through continually varying media or medium conditions54.Read more… at Penn State

Wind adds another layer of complexity. Sound travelling with the wind is refracted differently from sound travelling against it. Variations in wind speed at different heights can bend sound paths and distort perceived direction. Atmospheric infrasound research has shown that winds can alter the apparent arrival direction of distant acoustic signals enough to affect source-location estimates.

For witnesses already confronted with an unusual visual event, or with no visible source at all, these directional errors can reinforce the feeling that a sound is coming from an object in the sky.

Atmosphere illustration 2

Why Low-Frequency Sounds Feel Especially Mysterious

Many reports linked to UFO noises involve deep humming, rumbling or vibrations rather than sharp, easily identifiable sounds. Low-frequency sound behaves differently from higher-pitched noise.

Longer wavelengths are less easily blocked by buildings, vegetation and terrain. They can travel farther and remain audible even after higher frequencies have faded. This means that a distant industrial compressor, aircraft engine, ventilation system or transport corridor may be heard primarily as a low drone stripped of its more recognisable acoustic details. [Wikibooks]en.wikibooks.orgWikibooksEngineering Acoustics/Outdoor Sound PropagationOutdoor sound propagation is affected by spreading, absorption, ground configurat…

When listeners cannot identify the source, the brain often attempts to fill in the missing information. A vague mechanical vibration heard during a quiet night can feel far more mysterious than the same sound heard in daylight with visible context. This is one reason persistent hum phenomena and reports of strange atmospheric noises frequently attract speculation about secret technology, underground activity or UFOs. [The Natural Navigator]naturalnavigator.comsounds during a temperature inversionThe Natural NavigatorSounds during a temperature inversion7 Jan 2019 — Road noise travels much further during a temperature inversion. An…

Importantly, atmospheric acoustics does not require a sound to be imaginary. The sound can be completely real while its distance, direction and cause are misperceived.

ACOUSTICS: Refraction and Temperature Inversion

Channel: The Point Studios · Views: 9.2K · Uploaded: October 2012 · Length: 2 minutes 21 seconds

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What Are the Mystery Booms, Hums and "Trumpets" in the Sky? | Make This Make Sense

Channel: New York Post · Views: 20.1K · Uploaded: April 2026 · Length: 19 minutes

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Where Atmospheric Acoustics Fits in UFO Noise Reports

Atmospheric sound propagation is one of the strongest conventional explanations for reports of unidentified sky noises because it directly addresses a recurring feature of witness accounts: the sensation that a sound originates from empty air.

Temperature inversions, wind shear, stable nighttime conditions and long-range propagation are all well-established physical phenomena. They are routinely studied in environmental acoustics, aviation noise management and meteorology because they can dramatically alter what people hear on the ground. [Acoustics Today]acousticstoday.orgAcoustics Todaysound Propagation in the Atmospheric boundary layerJune 1, 2015 — by DK Wilson · Cited by 44 — A positive vertical gradient may be caused either by a ground- based temperature inversion, m…Published: June 1, 2015 [Dael Acoustics]dael.euracoustics.orgdT/dz = +10K/km, which is called thermal inversion, the sound rays are refracted downward, as shown in Fig…Read more…

That does not mean every unusual sound report has been solved. Some recordings remain difficult to trace, and in many cases there is insufficient information to identify a specific source. What atmospheric acoustics demonstrates is that the atmosphere itself can be an active participant in the experience. A witness may correctly hear a real sound while being misled about where it came from and how far away it truly was. [Acoustics Today]acousticstoday.orgAcoustics Todaysound Propagation in the Atmospheric boundary layerJune 1, 2015 — by DK Wilson · Cited by 44 — A positive vertical gradient may be caused either by a ground- based temperature inversion, m…Published: June 1, 2015 Wikipedia Within the broader subject of UFO noises [Wikipedia]WikipediaInversion (meteorologyInversion (meteorology)In meteorology, an inversion (or temperature inversion) is a phenomenon in which a layer of warmer air overlies…, this mechanism provides a practical reminder: an apparently skyborne sound does not necessarily require a skyborne source. The atmosphere can transform ordinary noise into something that feels detached, distant and unexplained. [Acentech]acentech.comAcentechCold Snaps and Sound Waves: Atmospheric AcousticsFeb 15, 2022 — This condition is called a temperature inversion, where the sound… [The Natural Navigator]naturalnavigator.comsounds during a temperature inversionThe Natural NavigatorSounds during a temperature inversion7 Jan 2019 — Road noise travels much further during a temperature inversion. An…

Atmosphere illustration 3

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Endnotes

  1. Source: en.wikibooks.org
    Link: https://en.wikibooks.org/wiki/Engineering_Acoustics/Outdoor_Sound_Propagation
    Source snippet

    WikibooksEngineering Acoustics/Outdoor Sound PropagationOutdoor sound propagation is affected by spreading, absorption, ground configurat...

  2. Source: acentech.com
    Link: https://www.acentech.com/resources/cold-snaps-and-sound-waves-atmospheric-acoustics/
    Source snippet

    AcentechCold Snaps and Sound Waves: Atmospheric AcousticsFeb 15, 2022 — This condition is called a temperature inversion, where the sound...

  3. Source: Wikipedia
    Title: Inversion (meteorology)
    Link: https://en.wikipedia.org/wiki/Inversion_%28meteorology%29
    Source snippet

    Inversion (meteorology)In meteorology, an inversion (or temperature inversion) is a phenomenon in which a layer of warmer air overlies...

  4. Source: ntrs.nasa.gov
    Title: Technical Reports Server Atmospheric Turbulence Effects on ‘ Aircraft Noise
    Link: https://ntrs.nasa.gov/api/citations/19800020594/downloads/19800020594.pdf
    Source snippet

    _radients can also be determined if profiles of the mean temperature and wind are known or measured. (...Read more...

  5. Source: sciencedirect.com
    Link: https://www.sciencedirect.com/science/article/abs/pii/S0003682X02001044
    Source snippet

    ScienceDirectSimulation of a morning air temperature inversion break-up...by LR Hole · 2003 · Cited by 18 — Sound propagation in the atm...

  6. Source: sciencedirect.com
    Link: https://www.sciencedirect.com/science/article/pii/S0022460X78800339
    Source snippet

    P.J. Dickinson. Temperature inversion effects on aircraft noise propagation. Journal of Sound and Vibration, 47 (1976)...

  7. Source: sky.com
    Link: https://www.sky.com/
    Source snippet

    Discover TV, Broadband & Mobile Phone Packages with SkyDiscover Sky packages for TV, broadband & mobile including Glass - the new streami...

  8. Source: Wikipedia
    Title: Sky UK
    Link: https://en.wikipedia.org/wiki/Sky_UK
    Source snippet

    Sky UKSky is a British broadcaster and telecommunications company that provides television, broadband internet, fixed line and mobile...

  9. Source: ntrs.nasa.gov
    Link: https://ntrs.nasa.gov/api/citations/20060049123/downloads/20060049123.pdf
    Source snippet

    5000 feet, changes in either temperature or humidity can easily cause changes of 5 dB in sound...Read more...

  10. Source: youtube.com
    Title: ACOUSTICS: Refraction and Temperature Inversion
    Link: https://www.youtube.com/watch?v=LkFQg1zhi2o
    Source snippet

    What Are the [Mystery Booms]({{ 'booms/' | relative_url }}), Hums and "Trumpets" in the Sky? | Make This Make Sense...

  11. Source: youtube.com
    Title: Conceptual Physics: Refraction of Sound
    Link: https://www.youtube.com/watch?v=z7RbHBK58h8
    Source snippet

    ACOUSTICS: Refraction and Temperature Inversion - YouTube ACOUSTICS: Refraction and Temperature Inversion - YouTube The Point Studios...

  12. 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

    June 1, 2015 — by DK Wilson · Cited by 44 — A positive vertical gradient may be caused either by a ground- based temperature inversion, m...

    Published: June 1, 2015

  13. Source: acousticstoday.org
    Link: https://acousticstoday.org/10-the-world-through-sound-reflection-refraction-and-the-principle-of-least-time/
    Source snippet

    Acoustics TodayReflection, Refraction, and the Principle of Least TimeFor sound, the most interesting effects occur when cold air gets tr...

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

    Simon Fraser UniversitySound PropagationHigher temperatures produce higher speeds of sound. Since the temperature of the atmosphere is no...

  15. Source: acoustics.org.nz
    Link: https://acoustics.org.nz/wp-content/uploads/Hannah_L_NZA2007_b.pdf
    Source snippet

    Refraction of sound is the bending of sound waves caused by propagation through continually varying media or medium conditions54.Read more...

  16. Source: dael.euracoustics.org
    Link: https://dael.euracoustics.org/confs/fa2023/data/articles/000175.pdf
    Source snippet

    dT/dz = +10K/km, which is called thermal inversion, the sound rays are refracted downward, as shown in Fig...Read more...

  17. Source: naturalnavigator.com
    Title: sounds during a temperature inversion
    Link: https://www.naturalnavigator.com/news/2019/01/sounds-during-a-temperature-inversion/
    Source snippet

    The Natural NavigatorSounds during a temperature inversion7 Jan 2019 — Road noise travels much further during a temperature inversion. An...

  18. Source: degruyterbrill.com
    Link: https://www.degruyterbrill.com/document/doi/10.1515/noise-2024-0006/html?srsltid=AfmBOoromiF7BlsOKRPGIZlobMAKsQeBDBzgp-6tHpV06II-s1804xVV
    Source snippet

    To study its variations over time and location due to solar...Read more...

  19. Source: thermaxxjackets.com
    Title: Thermaxx Jackets Refraction of Sound Waves & [Acoustic Shadows]({{ ‘sound-shadows/’ | relative_url }}) Explained
    Link: https://www.thermaxxjackets.com/news/sound-wave-refraction-acoustic-shadows/
    Source snippet

    Thermaxx JacketsRefraction of Sound Waves & Acoustic Shadows ExplainedMarch 17, 2017 — 17 Mar 2017 — In this article we are going to expl...

    Published: March 17, 2017

  20. Source: acs.psu.edu
    Link: https://www.acs.psu.edu/drussell/demos/refract/refract.html
    Source snippet

    of Sound Waves25 Jul 2025 — Acoustician Charles D. Ross has found that refraction of sound caused by temperature and wind gradients may h...

  21. Source: uswitch.com
    Link: https://www.uswitch.com/broadband/providers/sky/
    Source snippet

    Broadband Deals: Compare in May 2026Compare our range the latest Sky deals for fibre broadband, TV and home phone. Also browse Sky full f...

  22. Source: online.berklee.edu
    Title: acoustics in music
    Link: https://online.berklee.edu/takenote/acoustics-in-music/
    Source snippet

    in Music: Outdoor, Indoor, and Isolated Spaces18 Mar 2021 — From outdoor amphitheaters, to indoor concert halls, to sound-tight recording...

Additional References

  1. Source: weather.gov
    Link: https://www.weather.gov/source/zhu/ZHU_Training_Page/Miscellaneous/gravity_wave/gravity_wave.html
    Source snippet

    Gravity Wave/Undular Bore DefinedThe inversion itself plays two roles in the propagation of the wave. First, it enables the wave to conti...

  2. Source: weather.gov
    Link: https://www.weather.gov/
    Source snippet

    National Weather ServiceUnsettled Weather in the Eastern U.S. through Memorial Day · Frost Advisory · Rip Current Statement · Beach Hazar...

  3. Source: skygroup.sky
    Link: https://www.skygroup.sky/

  4. Source: skymedia.co.uk
    Link: https://www.skymedia.co.uk/
    Source snippet

    Welcome to Sky Media the advertising sales arm of SkyAs the ultimate aggregator of premium video content, we connect advertisers to an ex...

  5. Source: core.ac.uk
    Link: https://core.ac.uk/download/pdf/42864027.pdf
    Source snippet

    _radients can also be determined if profiles of the mean temperature and wind are known.Read more...

  6. Source: essd.copernicus.org
    Link: https://essd.copernicus.org/articles/13/3281/2021/essd-13-3281-2021.pdf
    Source snippet

    from the NOAA P-3 aircraft during ATOMICby R Pincus · 2021 · Cited by 35 — In particular, the directional wave spectra calcu- lated from...

  7. Source: scribd.com
    Link: https://www.scribd.com/document/655598115/Sound-Outdoors-from-Yamaha-book
    Source snippet

    een air layers with different wind speeds can also refract...Read more...

  8. Source: reddit.com
    Link: https://www.reddit.com/r/meteorology/comments/190cxpy/sound_travels_more_sometimes_and_i_dont_understand/
    Source snippet

    in a direct channel as well. Also, oftentimes the wind...Read more...

  9. Source: students.aip.org
    Title: physics puzzler sound reasons the answers
    Link: https://students.aip.org/observer/physics-puzzler-sound-reasons-the-answers
    Source snippet

    Puzzler: Sound Reasons: The Answers1 Feb 2016 — Sound travels faster in warmer air, so the sound waves are refracted upward, away from th...

  10. Source: comsol.com
    Title: why sounds travel farther at night
    Link: https://www.comsol.com/blogs/why-sounds-travel-farther-at-night
    Source snippet

    COMSOLWhy Sounds Travel Farther at Night28 Jan 2025 — The cause of this sound phenomenon is the change in temperature distribution in the...

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