Among the many questions that humanity has posed to the universe — the nature of consciousness, the origin of dark matter, the thermodynamic arrow of time — one has proven uniquely resistant to serious academic inquiry: can sound make you soil yourself?
The hypothesis, known colloquially as the “brown note,” posits that infrasound at some critical frequency might induce involuntary gastrointestinal distress. Despite decades of anecdote, no rigorous analytical treatment existed. We found this oversight unacceptable.
This repository models the human abdomen as a fluid-filled viscoelastic oblate spheroidal shell, derives its modal characteristics from first principles, and determines — with what we believe is an unprecedented level of analytical formality — that the answer is almost certainly no. The flexural resonance sits comfortably in the infrasonic band, but the airborne acoustic energy required to drive it meaningfully exceeds anything achievable outside of a Saturn V launch.
Whole-body vibration is another matter entirely, which is why we wrote five papers instead of one.
Modal analysis of a fluid-filled viscoelastic oblate spheroidal shell
Status: Submission-ready (~44 pages, 52 references)
Target venue: Journal of Sound and Vibration
Latest draft: PDF
Key result: coupling ratio R ≈ 6.6 × 10⁴
Can a sufficiently powerful subwoofer ruin your afternoon? We model the human abdomen as a fluid-filled viscoelastic oblate spheroidal shell, derive its modal spectrum from first principles, and compare airborne acoustic coupling with whole-body mechanical vibration. The resonance is real; the acoustic pathway to it is not.
Gas pocket resonance as an alternative acoustic coupling mechanism
Status: ACCEPT after internal review; submission-ready (~16 pages)
Target venue: JASA Express Letters
Latest draft: PDF
Key result: 35-100× more efficient than whole-cavity coupling
If the whole abdomen will not cooperate, perhaps the gas trapped inside it will. We model intestinal gas pockets as tissue-constrained bubbles and show they couple to airborne sound 35–100× more efficiently than the cavity itself — enough, at extreme SPL, to activate mechanosensitive ion channels in nearby tissue.
Dimensional analysis predictions across mammalian scales
Status: Under revision (8 pages)
Target venue: JSV Short Communication
Latest draft: PDF
Key result: Π₀ ≈ 0.07; the breathing mode wants an organism about 20 m long
Do rats, cats, pigs, and humans all resonate the same way, or is the brown note a uniquely human indignity? Buckingham Pi analysis reduces the ten-parameter shell problem to five governing groups, revealing a quasi-universal dimensionless frequency Π₀ ≈ 0.07 across species and a scattering coupling ratio that is approximately size-independent.
Resonance of the human urinary bladder
Status: Under development (20+ pages)
Target venue: Journal of Sound and Vibration
Latest draft: PDF
Key result: f₂ = 13.5 Hz at 222 mL
Anyone who has endured a long motorway journey on a full bladder has conducted an informal experiment in pelvic vibroacoustics. We apply the fluid-filled shell framework to the urinary bladder, finding a non-monotonic U-shaped frequency curve whose minimum coincides suspiciously with typical driving-posture fill volumes.
Multi-mode acoustic model of bowel sounds
Status: First draft complete (17 pages)
Target venue: JASA
Latest draft: PDF
Key result: 135-440 Hz constrained bubble model
Your stomach growls. What pitch is it, exactly, and why? We develop a five-mechanism acoustic model — from free Minnaert bubbles through tissue-constrained oscillations to Helmholtz orifice resonance — that predicts the clinically observed 200–550 Hz bowel sound band without tuning.
Mid-Tenure Research Statement — Research vision, accomplishments, and trajectory for the Browntone programme.
The abdomen does have a low-order flexural resonance near 4 Hz, so the folk intuition is not completely mad. What fails is the coupling: even at 120 dB SPL, the energy-consistent airborne displacement is only about 0.014 μm, around four orders of magnitude below mechanotransduction thresholds. Whole-body vibration, by contrast, produces millimetre-scale effective excitation of the relevant mode. In short: the “brown note” is a mechanical story misremembered as an acoustic one.
| Quantity | Value |
|---|---|
| n=2 flexural frequency (f₂) | 3.95 Hz |
| Breathing mode (n=0) | 2,490 Hz |
| Airborne displacement (ξ_air, 120 dB) | 0.014 μm |
| Mechanical displacement (ξ_mech, 0.5 m/s²) | 4,586 μm |
| Coupling ratio R | ≈ 66,000× (6.6×10⁴) |
| Sobol total-order index S_T(E) | 0.86 |
This repository was built with GitHub Copilot CLI and a small bureaucracy of autonomous AI agents handling analysis, drafting, review, figure generation, and repo maintenance. The current tally is roughly 300 commits, 117 pull requests merged, 203 tests passing, 17 custom agents, 16 reusable skills, 57+ research logs, and about 24 hours of wall-clock interaction time.
The active agent roster lives in .github/agents/ and currently includes the review panel (reviewer-a, reviewer-b, reviewer-c), infrastructure roles (chief-of-staff, lab-manager, lab-meeting), editorial triage via journal-editor, production roles (paper-writer, simulation-engineer, data-analyst, communications, bibliographer), and specialist characters such as pop-culture-verifier, provocateur, research-scout, coffee-machine-guru, and loving-spouse.
See docs/ai-assisted-research.md for the workflow notes.
pip install -e .[dev]
python -m pytest tests/ -vimport sys
sys.path.insert(0, r"C:\path\to\browntone")
from src.analytical.natural_frequency_v2 import (
AbdominalModelV2,
flexural_mode_frequencies_v2,
)
from src.analytical.energy_budget import self_consistent_displacement
from src.analytical.mechanical_coupling import mechanical_coupling_analysis
model = AbdominalModelV2(
E=0.1e6,
a=0.18,
c=0.12,
h=0.01,
nu=0.45,
rho_wall=1100,
rho_fluid=1020,
K_fluid=2.2e9,
P_iap=1000,
loss_tangent=0.25,
)
freqs = flexural_mode_frequencies_v2(model, n_max=5)
disp = self_consistent_displacement(model, mode_n=2, spl_db=120)
mech = mechanical_coupling_analysis(model)If you only want one number, ask the model for the n=2 flexural mode. If you want the whole joke explained properly, read Paper 1.
browntone/
├── paper/ # Paper 1: brown note manuscript + drafts
├── paper2-gas-pockets/ # Paper 2: gas-pocket resonance
├── paper3-scaling-laws/ # Paper 3: dimensional analysis note
├── projects/
│ ├── bladder-resonance/ # Paper 4
│ └── borborygmi/ # Paper 5
├── src/analytical/ # Core analytical models
├── tests/ # Pytest regression suite
├── docs/research-logs/ # Quantitative research logs
└── .github/ # Agents, skills, workflows, instructions
The analytical suite currently has 203 passing tests. From the repository root:
python -m pytest tests/ -v| Who | Affiliation | Role |
|---|---|---|
| Jonathan Mace | MSR | Lead author, concept, writing, supervision |
| Brian R. Mace | University of Auckland | Vibroacoustics expertise, theory, supervision |
| GitHub Copilot CLI (Opus) | GitHub, Inc. | Analysis, drafting, review orchestration, code |
| Springbank 10 Year Old | Campbeltown, Scotland | Moral support, tonal calibration, occasional strategic clarity |