Within Acoustics
The Delayed Boom After a Meteor
Very low-frequency sound can arrive after a bright meteor and help separate a distant shock event from a nearby aircraft or drone.
On this page
- Why bolides can produce infrasound
- How delayed low frequency signals help classification
- Why audible silence can still fit a meteor
Page outline Jump by section
Introduction
A bright meteor or bolide can look like a nearby explosion even when it occurs tens of kilometres above the Earth. One of the most useful ways to distinguish such events from aircraft, drones or local explosions is to examine their infrasound: extremely low-frequency acoustic waves below the normal range of human hearing. Unlike light, these waves travel at the speed of sound, so they often arrive minutes after the visual event. That delayed arrival is not a flaw in the evidence but an expected consequence of atmospheric physics, and it has become an important classification tool in modern automated sky-monitoring systems. [CTBTO]ctbto.orgInfrasound monitoringAcoustic waves with very low frequencies are called infrasound…. infrasound monitoring is a useful technique…
For automated instrumented UFO detectors, infrasound is valuable because it provides an independent measurement that can either support or weaken a meteor explanation. When a brilliant fireball is followed by a delayed low-frequency signal arriving from the correct direction and with the expected timing, the combined evidence strongly favours a distant atmospheric bolide over a nearby aircraft, drone or ground-level blast.
Why bolides can produce infrasound
A bolide enters the atmosphere at many kilometres per second, far exceeding the speed of sound. Instead of producing a single point explosion, it commonly generates a moving shock wave along much of its flight path. If the object fragments violently, additional blast waves may be created at one or more breakup points.
Much of the resulting acoustic energy lies below about 20 Hz, making it inaudible to humans but detectable by sensitive microbarometers. These infrasonic waves lose comparatively little energy over long distances and can propagate through atmospheric layers for hundreds or even thousands of kilometres. That is why dedicated infrasound networks routinely detect large fireballs that occurred far beyond the range where anyone could hear an ordinary sonic boom. [CTBTO+2MDPI]ctbto.orgInfrasound monitoringAcoustic waves with very low frequencies are called infrasound…. infrasound monitoring is a useful technique…
Modern studies also show that meteor-generated infrasound is more complicated than a simple explosion. Analysts may observe signals produced by:
- the continuous shock along the flight path;
- one or more major fragmentation events;
- reflections and refractions through different atmospheric layers;
- multiple arrivals from different propagation paths.
Recognising these patterns helps estimate where the strongest breakup occurred and how much energy the bolide released. [MDPI+2arXiv]mdpi.comPerspectives and Challenges in Bolide Infrasound…by EA Silber · 2024 · Cited by 16 — Infrasound sensing plays a critical role in t…
How delayed low-frequency signals help classification
The delay between the flash and the acoustic arrival is one of the strongest clues available to an automated observing system.
Light reaches cameras almost instantly, whereas sound travels through the atmosphere at roughly 340 metres per second near the ground. A meteor exploding 50–100 km away can therefore produce a visible flash followed by an acoustic arrival several minutes later. The larger the separation, the longer the expected delay.
This timing changes how an event should be interpreted.
- Nearby aircraft or drones generally produce continuous audible sound closely associated with their apparent position.
- Ground explosions produce acoustic arrivals consistent with a fixed surface location.
- Bolides often generate no immediate audible sound but later produce infrasonic or low-frequency arrivals consistent with a distant, elevated moving source.
Rather than treating the absence of immediate sound as suspicious, automated systems can predict when an infrasonic signal should arrive based on the estimated trajectory. Agreement between predicted and measured arrival times substantially increases confidence that the event was a meteor rather than an unidentified nearby object. [MDPI+2arXiv]mdpi.comPerspectives and Challenges in Bolide Infrasound…by EA Silber · 2024 · Cited by 16 — Infrasound sensing plays a critical role in t…
This approach is especially valuable when optical imagery alone leaves room for multiple interpretations because of uncertain distance or perspective.
Why audible silence can still fit a meteor
Witnesses often report that a spectacular fireball was “completely silent”. Without understanding atmospheric acoustics, this can seem inconsistent with such an energetic event.
In reality, silence at the moment of observation is exactly what physics predicts for most meteors.
Because the luminous phase occurs high in the atmosphere, the flash reaches observers long before any acoustic wave. Many events are also simply too distant for ordinary audible frequencies to survive propagation, even though the lower-frequency infrasonic components continue travelling efficiently. Automated detectors therefore treat immediate silence as neutral evidence rather than evidence against a meteor explanation. [CTBTO+2MDPI]ctbto.orgInfrasound monitoringAcoustic waves with very low frequencies are called infrasound…. infrasound monitoring is a useful technique…
An important exception sometimes appears in eyewitness reports: so-called electrophonic sounds. These are simultaneous hissing, crackling or sizzling sounds reported during exceptionally bright meteors. They are thought not to be ordinary acoustic waves travelling from the meteor itself but local sounds generated when very low frequency electromagnetic fields induce vibrations in nearby objects. Such reports remain rare and scientifically challenging, and they should not be confused with delayed infrasonic shock waves. [ETHW+2vinkovic.org]ethw.orgElectrophonic MeteorsElectrophonic MeteorsSeptember 17, 2015 — 17 Sept 2015 — The perceived improbability of electrophonic meteors has prevented substanti…
Real examples that changed interpretation
The 2013 Chelyabinsk bolide demonstrated the power of infrasound for understanding major atmospheric impacts. The event produced one of the strongest infrasonic signals ever recorded by the global monitoring network operated for the Comprehensive Nuclear-Test-Ban Treaty. Multiple stations across continents detected the signal, with some observations made roughly 15,000 km from the source. Analysts used the changing direction and timing of the arriving waves to distinguish the moving meteor from a stationary explosion and to estimate its energy release. [CTBTO]ctbto.orgrussian fireball largest ever detected ctbtos infrasoundRussian Fireball Largest Ever Detected by CTBTO's…Feb 18, 2013 — Infrasonic waves from the meteor that broke up over Russia's Ura…
Researchers have since analysed many dozens of bolides detected by worldwide infrasound arrays. Combining optical observations with infrasonic measurements allows estimates of fragmentation altitude, energy yield and trajectory that would be difficult from cameras alone. Recent reviews emphasise that interpreting these signals requires accounting for atmospheric winds, propagation paths and the fact that extended meteor trajectories generate more complex acoustic signatures than simple point explosions. [MDPI+2arXiv]mdpi.comPerspectives and Challenges in Bolide Infrasound…by EA Silber · 2024 · Cited by 16 — Infrasound sensing plays a critical role in t…
What this means for automated UFO detectors
Within an automated instrumented UFO detection system, infrasound is most valuable when fused with optical and timing information rather than treated as a standalone identifier.
A practical classification workflow can compare:
- the time of the optical flash;
- the expected acoustic travel time;
- the arrival direction of the infrasonic signal;
- whether the signal resembles a moving atmospheric source rather than a local explosion;
- consistency with meteor trajectory estimates from cameras.
When these measurements agree, the system gains objective evidence that a visually dramatic but initially silent event was a distant bolide. Conversely, if a supposed meteor lacks any compatible delayed infrasonic signature despite favourable observing geometry, investigators have reason to examine alternative explanations or consider whether the optical observation was incomplete.
In this way, infrasound does not merely detect meteors. It changes how ambiguous sky events are interpreted by adding an independent physical measurement that can separate distant atmospheric impacts from nearby human-made sources, reducing false classifications in automated sky-monitoring networks. [MDPI+2arXiv]mdpi.comPerspectives and Challenges in Bolide Infrasound…by EA Silber · 2024 · Cited by 16 — Infrasound sensing plays a critical role in t…
Amazon book picks
Further Reading
Books and field guides related to The Delayed Boom After a Meteor. Use these as the next step if you want deeper reading beyond the article.
Meteor Science and Engineering
Explains meteor physics behind delayed acoustic signals.
Fundamentals of acoustics
First published 2000. Subjects: Sound, Equipment and supplies, Architectural acoustics, Sound-waves, Sound, equipment and supplies.
eBay marketplace picks
Marketplace Samples
Live-tested eBay searches with available results related to this page.
Endnotes
-
Source: ctbto.org
Link: https://www.ctbto.org/our-work/monitoring-technologies/infrasound-monitoringSource snippet
Infrasound monitoringAcoustic waves with very low frequencies are called infrasound.... infrasound monitoring is a useful technique...
-
Source: mdpi.com
Link: https://www.mdpi.com/2072-4292/16/19/3628Source snippet
Perspectives and Challenges in Bolide Infrasound...by EA Silber · 2024 · Cited by 16 — Infrasound sensing plays a critical role in t...
-
Source: arxiv.org
Title: arXiv Refinement of Bolide Characteristics from Infrasound measurements
Link: https://arxiv.org/abs/1704.07794 -
Source: arxiv.org
Link: https://arxiv.org/abs/2405.04127Source snippet
The utility of infrasound in global monitoring of extraterrestrial impacts: A case study of the 23 July 2008 Tajikistan bolide...
Published: July 2008
-
Source: arxiv.org
Link: https://arxiv.org/abs/2503.13972 -
Source: ethw.org
Title: Electrophonic Meteors
Link: https://ethw.org/Electrophonic_MeteorsSource snippet
Electrophonic MeteorsSeptember 17, 2015 — 17 Sept 2015 — The perceived improbability of electrophonic meteors has prevented substanti...
Published: September 17, 2015
-
Source: vinkovic.org
Link: https://vinkovic.org/Projects/Electrophones/Vinkovic_2002_WGN_30_244.pdfSource snippet
Global Electrophonic Fireball Survey: a [review]({{ 'review/' | relative_url }}) of witness...Audible sounds from meteors can be divided into two groups: normal and anoma...
-
Source: ctbto.org
Title: russian fireball largest ever detected ctbtos infrasound
Link: https://www.ctbto.org/resources/for-the-media/press-releases/russian-fireball-largest-ever-detected-ctbtos-infrasoundSource snippet
Russian Fireball Largest Ever Detected by CTBTO's...Feb 18, 2013 — Infrasonic waves from the meteor that broke up over Russia's Ura...
-
Source: ctbto.org
Link: https://www.ctbto.org/Source snippet
HomepageJoin CTBTO on our mission to create a world free of nuclear testing. Learn more about employment and business opportunitie...
-
Source: ctbto.org
Link: https://www.ctbto.org/news-and-events/news/ctbto-infrasound-stations-detect-russian-meteorite-blastSource snippet
CTBTO Infrasound Stations Detect Russian Meteorite BlastThe low frequency sound waves from the blast were detected at 03:22 GMT by the ne...
-
Source: conferences.ctbto.org
Link: https://conferences.ctbto.org/event/30/contributions/5515/attachments/3289/6616/E-poster_P1.1-227.pdfSource snippet
bolide shock source and propagation variability...23 Jul 2008 — Infrasound captures explosive bolide events from thousands of kilometers...
-
Source: ctbto.org
Link: https://www.ctbto.org/our-work/international-monitoring-system -
Source: conferences.ctbto.org
Title: SnT2025 E Poster Albuquerque DF P5.1 830
Link: https://conferences.ctbto.org/event/30/contributions/6124/attachments/3218/6394/SnT2025_E-Poster_Albuquerque_DF_P5.1-830.pdfSource snippet
of infrasound generated by the meteoroid...Nov 29, 2020 — The bolide had a yield of less than 1 kt TNT estimated by CNEOS, showing that...
-
Source: youtube.com
Title: Nothing Escapes The Global Ear: Nuclear Tests, Volcanoes, Earthquakes or Meteors
Link: http://www.youtube.com/watch?v=lWCzSAEtbbUSource snippet
CTBTO Russian meteor infrasound Russian Fireball Largest Ever Detected by CTBTO's Infrasound Sensors...
Additional References
-
Source: aquarid.physics.uwo.ca
Link: https://aquarid.physics.uwo.ca/research/infrasound/is_advantages.htmlSource snippet
Meteor InfrasoundInfrasound detection is a robust, cost effective technology for detection of blast waves from bolides. It is possible to...
-
Source: reddit.com
Link: https://www.reddit.com/r/space/comments/1c6e5nh/meteor_making_noise/Source snippet
Meteor making noise??: r/spaceI live in Santa Clarita, CA, a northern suburb of Los Angeles. Last night around 8pm, many residents of th...
-
Source: scitechdaily.com
Title: sonic booms in the sky how scientists use bolides to improve planetary defense
Link: https://scitechdaily.com/sonic-booms-in-the-sky-how-scientists-use-bolides-to-improve-planetary-defense/Source snippet
Sonic Booms in the Sky: How Scientists Use “Bolides” To...2 Jul 2025 — Scientists are now exploring how mysterious sky-booms known as bo...
-
Source: physics.stackexchange.com
Title: was carl sagan correct to say that meteor entry is completely silent
Link: https://physics.stackexchange.com/questions/873405/was-carl-sagan-correct-to-say-that-meteor-entry-is-completely-silentSource snippet
Carl Sagan correct to say that meteor entry is "...16 Jun 2026 — In Broca's Brain (1979), Carl Sagan criticized a statement by Immanuel...
-
Source: unoosa.org
Title: Putting an end to nuclear explosions through science
Link: https://www.unoosa.org/documents/pdf/WSF/Presentations/Session/UN-Space/6._Martin_CTBTO_UNOOSApanel_NEO_20Nov2019.pdfSource snippet
detected by CTBTO infrasound sensors. Geophysical Research Letters, DOI... The most energetic event since the Tungunska meteor. (1908)...
-
Source: researchgate.net
Link: https://www.researchgate.net/publication/351278914_Electrophonic_sounds_from_meteors_and_auroral_audibilitySource snippet
without delay). They are known for hundreds years. At least several hypotheses...
-
Source: phys.org
Title: 2013 02 russian fireball largest ctbto infrasound
Link: https://phys.org/news/2013-02-russian-fireball-largest-ctbto-infrasound.htmlSource snippet
Russian fireball largest ever detected by CTBTO's...19 Feb 2013 — Infrasound has been used as part of the CTBTO's tools to detect atomic...
-
Source: space.com
Title: 19860 russia meteor explosion largest detected
Link: https://www.space.com/19860-russia-meteor-explosion-largest-detected.htmlSource snippet
Russia Meteor Blast Largest Seen by Nuclear Detection GridFeb 19, 2013 — When the space rock detonated, the blast was detected by 17 infr...
-
Source: csmonitor.com
Title: Russia meteor triggered nuclear warning system
Link: https://www.csmonitor.com/Science/2013/0222/Russia-meteor-triggered-nuclear-warning-systemSource snippet
Feb 22, 2013 — When the space rock detonated, the blast was detected by 17 infrasound stations in the CTBTO's network that track atomic b...
-
Source: researchgate.net
Title: 316520644 Infrasound detection of meteors
Link: https://www.researchgate.net/publication/316520644_Infrasound_detection_of_meteorsSource snippet
(PDF) Infrasound detection of meteors28 Apr 2017 — Meteorites that penetrate the atmosphere generate infrasound waves of very low frequen...
Topic Tree