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Title: Photoacoustic sounds from meteors

Abstract

Concurrent sound associated with very bright meteors manifests as popping, hissing, and faint rustling sounds occurring simultaneously with the arrival of light from meteors. Numerous instances have been documented with –11 to –13 brightness. These sounds cannot be attributed to direct acoustic propagation from the upper atmosphere for which travel time would be several minutes. Concurrent sounds must be associated with some form of electromagnetic energy generated by the meteor, propagated to the vicinity of the observer, and transduced into acoustic waves. Previously, energy propagated from meteors was assumed to be RF emissions. This has not been well validated experimentally. Herein we describe experimental results and numerical models in support of photoacoustic coupling as the mechanism. Recent photometric measurements of fireballs reveal strong millisecond flares and significant brightness oscillations at frequencies ≥40 Hz. Strongly modulated light at these frequencies with sufficient intensity can create concurrent sounds through radiative heating of common dielectric materials like hair, clothing, and leaves. This heating produces small pressure oscillations in the air contacting the absorbers. Calculations show that –12 brightness meteors can generate audible sound at ~25 dB SPL. As a result, the photoacoustic hypothesis provides an alternative explanation for this longstanding mystery about generationmore » of concurrent sounds by fireballs.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [2]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  2. Czech Academy of Sciences, Ondrejov (Czech Republic)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1345579
Report Number(s):
SAND-2015-3780J
Journal ID: ISSN 2045-2322; srep41251
Grant/Contract Number:
AC04-94AL85000
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION

Citation Formats

Spalding, Richard, Tencer, John, Sweatt, William, Conley, Benjamin, Hogan, Roy, Boslough, Mark, Gonzales, GiGi, and Spurny, Pavel. Photoacoustic sounds from meteors. United States: N. p., 2017. Web. doi:10.1038/srep41251.
Spalding, Richard, Tencer, John, Sweatt, William, Conley, Benjamin, Hogan, Roy, Boslough, Mark, Gonzales, GiGi, & Spurny, Pavel. Photoacoustic sounds from meteors. United States. doi:10.1038/srep41251.
Spalding, Richard, Tencer, John, Sweatt, William, Conley, Benjamin, Hogan, Roy, Boslough, Mark, Gonzales, GiGi, and Spurny, Pavel. Wed . "Photoacoustic sounds from meteors". United States. doi:10.1038/srep41251. https://www.osti.gov/servlets/purl/1345579.
@article{osti_1345579,
title = {Photoacoustic sounds from meteors},
author = {Spalding, Richard and Tencer, John and Sweatt, William and Conley, Benjamin and Hogan, Roy and Boslough, Mark and Gonzales, GiGi and Spurny, Pavel},
abstractNote = {Concurrent sound associated with very bright meteors manifests as popping, hissing, and faint rustling sounds occurring simultaneously with the arrival of light from meteors. Numerous instances have been documented with –11 to –13 brightness. These sounds cannot be attributed to direct acoustic propagation from the upper atmosphere for which travel time would be several minutes. Concurrent sounds must be associated with some form of electromagnetic energy generated by the meteor, propagated to the vicinity of the observer, and transduced into acoustic waves. Previously, energy propagated from meteors was assumed to be RF emissions. This has not been well validated experimentally. Herein we describe experimental results and numerical models in support of photoacoustic coupling as the mechanism. Recent photometric measurements of fireballs reveal strong millisecond flares and significant brightness oscillations at frequencies ≥40 Hz. Strongly modulated light at these frequencies with sufficient intensity can create concurrent sounds through radiative heating of common dielectric materials like hair, clothing, and leaves. This heating produces small pressure oscillations in the air contacting the absorbers. Calculations show that –12 brightness meteors can generate audible sound at ~25 dB SPL. As a result, the photoacoustic hypothesis provides an alternative explanation for this longstanding mystery about generation of concurrent sounds by fireballs.},
doi = {10.1038/srep41251},
journal = {Scientific Reports},
number = ,
volume = 7,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2017},
month = {Wed Feb 01 00:00:00 EST 2017}
}

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  • High-speed photometric observations of meteor fireballs have shown that they often produce high-amplitude light oscillations with frequency components in the kHz range, and in some cases exhibit strong millisecond flares. We built a light source with similar characteristics and illuminated various materials in the laboratory, generating audible sounds. Models suggest that light oscillations and pulses can radiatively heat dielectric materials, which in turn conductively heats the surrounding air on millisecond timescales. The sound waves can be heard if the illuminated material is sufficiently close to the observer’s ears. The mechanism described herein may explain many reports of meteors that appearmore » to be audible while they are concurrently visible in the sky and too far away for sound to have propagated to the observer. This photoacoustic (PA) explanation provides an alternative to electrophonic (EP) sounds hypothesized to arise from electromagnetic coupling of plasma oscillation in the meteor wake to natural antennas in the vicinity of an observer.« less
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