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arxiv: 2604.12723 · v1 · submitted 2026-04-14 · 🌌 astro-ph.EP · astro-ph.IM

A Search for Hydroacoustic Signals from Bolides

P. Brown , L. McFadden , D. McCormack , M. Adams , D. Vida This is my paper

Pith reviewed 2026-05-10 14:29 UTC · model grok-4.3

classification 🌌 astro-ph.EP astro-ph.IM
keywords hydroacoustic signalsfireballsbolidesocean sound channelenergy coupling efficiencymeteoroid entryacoustic propagationatmospheric impacts
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The pith

No unambiguous hydroacoustic signals from fireballs appear in 53 station pairs, yielding a coupling efficiency upper limit of order 10 to the minus 10.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper surveys possible hydroacoustic signals generated when fireballs enter the atmosphere and checks for direct transmissions through the ocean sound channel to listening stations. It selects 30 fireballs with viable paths to stations, including high-energy cases and those over oceans, then examines 53 total associations using fixed signal speed and processing rules. No clear signals stand out above background noise levels. This lack of detections supports the conclusion that such signals are very rare and allows derivation of a tight upper bound on the fraction of fireball energy that couples into the sound channel. A sympathetic reader would care because the result shows ocean sound recordings are unlikely to serve as a practical tool for tracking most incoming meteors and quantifies how little atmospheric energy reaches deep underwater sound paths.

Core claim

We find no unambiguous detections in 53 station-fireball pairs. Based on SOFAR-equivalent yields derived assuming the minimum detectable amplitude signal family association is representative of the noise background in our survey we estimate a conditional upper limit for fireball coupling efficiency of order 10^{-10}. Hydroacoustic detection in the deep ocean sound channel of fireballs is very rare. One possible but statistically weak candidate exists from an event off Alaska in 2003. In contrast, an airplane impact provides an empirical coupling efficiency of 10^{-4} for high-velocity surface ocean strikes. Direct hydroacoustic shock transmission is identified as the most probable mechanism,

What carries the argument

Direct-path H-phase hydroacoustic signals identified via a fixed celerity window of 1.42-1.55 km/s and chosen signal processing parameters, used to test associations and derive the coupling-efficiency bound from the absence of detections above background.

If this is right

  • Hydroacoustic networks will rarely if ever register fireball events under standard direct-path assumptions.
  • Energy transfer from atmospheric fireballs to the ocean sound channel is at least four orders of magnitude weaker than from high-speed surface impacts.
  • Only extreme cases of large meteorites striking the ocean surface directly could produce detectable hydroacoustic signals.
  • Models of bolide entry must incorporate very low acoustic coupling efficiencies when predicting ocean interactions.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Most fireball energy dissipates in the upper atmosphere before any significant fraction can reach the ocean surface.
  • Cross-checking the same fireball events against seismic or infrasound records could test whether weak signals were missed by the hydroacoustic filters.
  • Widening the search to include reflected or longer-range propagation paths might uncover marginal detections not captured by the direct-path celerity window.

Load-bearing premise

The chosen celerity range together with the selected signal processing parameters will capture any real direct signals from fireballs while the background rate of signals is random and representative of the true noise floor.

What would settle it

A hydroacoustic arrival whose timing, back-azimuth, and amplitude precisely match a known fireball's location and predicted path, standing clearly above the surveyed noise level, would falsify both the no-detection result and the derived coupling limit.

Figures

Figures reproduced from arXiv: 2604.12723 by D. McCormack, D. Vida, L. McFadden, M. Adams, P. Brown.

Figure 1
Figure 1. Figure 1: The location of infrasound, hydrophone, and T-phase stations (seismometers on islands [PITH_FULL_IMAGE:figures/full_fig_p005_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Figure adapted from a similar plot in Urick (1975). This shows acoustic sound speed as [PITH_FULL_IMAGE:figures/full_fig_p009_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: The estimated peak pressure as a function of range for different TNT equivalent explosive [PITH_FULL_IMAGE:figures/full_fig_p011_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Terminal impact energy of different sized spherical iron and stony meteorites. [PITH_FULL_IMAGE:figures/full_fig_p017_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: The PMCC 1h window from the H03N station for the September 2, 2003 event. The top [PITH_FULL_IMAGE:figures/full_fig_p023_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Same as figure 5 but zoomed in around the time of the signal and filtered from 4 - 9 Hz. [PITH_FULL_IMAGE:figures/full_fig_p024_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Stacked best beam (lower plot) filtered from 4 - 9 Hz for the signal provisionally associated [PITH_FULL_IMAGE:figures/full_fig_p024_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Location of the September 2, 2003 fireball in relation to HS station H03. The blue line [PITH_FULL_IMAGE:figures/full_fig_p025_8.png] view at source ↗
read the original abstract

Here we present a survey aimed at detecting hydroacoustic signals from fireballs using the six hydrophone stations operated as part of the Comprehensive Test Ban Treaty Organisation (CTBTO) International Monitoring System. We identified 30 fireballs where propagation paths to stations exist. These included high energy fireballs (E $\geq$ 5 kT), those which occurred over favorable locations for coupling into the deep ocean as well as a selection of bolides close to CTBTO hydrophone stations. The largest of these impactors were $>$ 5 meters in diameter. From theoretical and empirical considerations we show that direct hydroacoustic shock transmission is the most likely source mechanism, though large meteorites impacting the ocean surface from a fireball might be detectable in extreme cases. We find one possible instance of a fireball occurring on Sep 2, 2003 off the coast of Alaska, where a linked hydroacoustic signal with the expected timing and backazimuth is detected. However, given the size of our survey and the random background rate of signals, this detection is statistically weak. We conclude that hydroacoustic detection in the SOFAR channel of fireballs is very rare. Using our chosen set of signal processing parameters, assuming direct path H-phase signals, adopting a signal celerity range of 1.42-1.55 km/s we find no unambigous detections in 53 station-fireball pairs. Based on SOFAR-equivalent yields derived assuming the minimum detectable amplitude signal family association is representative of the noise background in our survey we estimate a conditional upper limit for fireball coupling efficiency of order 10$^{-10}$. A single well recorded airplane impact provides an empirical estimate for the energy coupling of surface ocean impacts to the SOFAR channel of 10$^{-4}$ for high velocity surface impacts.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 3 minor

Summary. The paper reports a survey searching for hydroacoustic signals from 30 fireballs (including high-energy events >5 m diameter) using the six CTBTO IMS hydrophone stations. It identifies 53 station-fireball pairs with propagation paths, finds no unambiguous detections (one statistically weak candidate on 2 Sep 2003), and derives a conditional upper limit on fireball-to-SOFAR coupling efficiency of order 10^{-10} under the assumptions of direct-path H-phase signals, a celerity window of 1.42-1.55 km/s, and chosen signal-processing parameters. An empirical coupling efficiency of 10^{-4} is also reported from a single well-recorded airplane ocean impact.

Significance. If the non-detection result is robust, the work supplies a useful empirical constraint on the (very low) efficiency with which fireball energy couples into the SOFAR channel, relevant to both meteor physics and CTBTO hydroacoustic monitoring. The survey design (covering high-energy and geographically favorable events) and the airplane-impact calibration are concrete strengths that could be cited in future studies of impact-generated acoustic signals.

major comments (2)
  1. [Abstract] Abstract: the conditional upper limit of order 10^{-10} on coupling efficiency is derived from non-detections under a specific signal model (direct-path H-phase arrivals within 1.42-1.55 km/s celerity and fixed processing parameters). No injection study, completeness calculation, or quantitative assessment of alternative coupling mechanisms (surface shock, multipath, or out-of-band celerity) is provided; without this, the non-detection cannot be translated into a model-independent constraint and the limit remains conditional on untested assumptions about signal morphology.
  2. [Abstract] Abstract: the claim that the single candidate event is statistically weak rests on an adopted background rate of signals, yet the manuscript supplies no explicit calculation of that rate, no error bars, and no description of the data-exclusion rules used to define the noise floor. This information is required to evaluate the significance of the non-detection result and the resulting upper limit.
minor comments (3)
  1. [Abstract] Abstract contains the typo 'unambigous' (should be 'unambiguous').
  2. Terminology is inconsistent: the title uses 'Bolides' while the abstract and text predominantly use 'fireballs'. A single term should be adopted throughout.
  3. A summary table listing the 30 fireballs, their energies, locations, and station pairings would improve readability and allow readers to assess the survey coverage directly.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful and constructive review of our manuscript. We address each major comment below, indicating where we agree and where revisions will be incorporated.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the conditional upper limit of order 10^{-10} on coupling efficiency is derived from non-detections under a specific signal model (direct-path H-phase arrivals within 1.42-1.55 km/s celerity and fixed processing parameters). No injection study, completeness calculation, or quantitative assessment of alternative coupling mechanisms (surface shock, multipath, or out-of-band celerity) is provided; without this, the non-detection cannot be translated into a model-independent constraint and the limit remains conditional on untested assumptions about signal morphology.

    Authors: We agree that the upper limit is conditional on the direct-path H-phase model, the specified celerity window, and our fixed processing parameters, as already stated explicitly in the abstract and methods. These assumptions follow from standard hydroacoustic propagation theory for the SOFAR channel and the IMS network's typical detection approach, which we justify in the manuscript on the basis of theoretical and empirical considerations favoring direct shock transmission. The survey was designed around real events with known propagation paths rather than simulations, so no injection study was performed. We will revise the abstract and discussion sections to more clearly state that the limit is not model-independent and to note the lack of quantitative evaluation for alternatives such as surface shocks or multipath, while retaining the conditional bound as a useful empirical constraint for CTBTO-relevant monitoring. revision: partial

  2. Referee: [Abstract] Abstract: the claim that the single candidate event is statistically weak rests on an adopted background rate of signals, yet the manuscript supplies no explicit calculation of that rate, no error bars, and no description of the data-exclusion rules used to define the noise floor. This information is required to evaluate the significance of the non-detection result and the resulting upper limit.

    Authors: We acknowledge that the manuscript does not provide an explicit calculation of the background rate, error bars, or data-exclusion rules. In the revised manuscript we will add this information, including a quantitative estimate of the background signal rate derived from the full dataset, Poisson-based error bars on the expected number of false associations, and a description of the criteria used to exclude periods of elevated noise when defining the detection threshold. This will allow readers to independently assess the statistical weakness of the 2 September 2003 candidate. revision: yes

Circularity Check

0 steps flagged

No circularity: upper limit follows directly from non-detections under stated external assumptions

full rationale

The paper conducts an observational search across 53 station-fireball pairs using CTBTO hydrophone data, reports no unambiguous detections, and derives a conditional upper limit on coupling efficiency from the minimum detectable amplitude and an externally adopted celerity window (1.42-1.55 km/s). No equations or steps reduce the claimed result to a fitted parameter, self-defined quantity, or self-citation chain; the derivation remains self-contained against the survey data and independent signal-model assumptions without internal loop-back.

Axiom & Free-Parameter Ledger

2 free parameters · 1 axioms · 0 invented entities

The upper limit rests on adopted parameters for signal detection and propagation that are not derived within the paper.

free parameters (2)
  • signal celerity range = 1.42-1.55 km/s
    Adopted range of 1.42-1.55 km/s for H-phase signals.
  • signal processing parameters
    Chosen set of parameters used to identify candidate signals.
axioms (1)
  • domain assumption Direct hydroacoustic shock transmission is the most likely source mechanism for any detectable signal.
    Stated explicitly in the abstract as the basis for expected signals.

pith-pipeline@v0.9.0 · 5640 in / 1369 out tokens · 46016 ms · 2026-05-10T14:29:35.021742+00:00 · methodology

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Reference graph

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