01. What is infrasound, and why does it matter?
Infrasound refers to acoustic pressure waves below roughly 20 Hz — the lower boundary of typical human hearing. These frequencies are produced by industrial machinery, large fans, compressors, rail traffic, and heavy vehicles. Although most people cannot consciously hear them, research has established that the inner ear continues to respond to infrasonic energy, particularly through structures that govern balance rather than sound perception.
The outer hair cells (OHC) of the cochlea appear to respond to infrasound at levels significantly below the threshold of conscious hearing. Salt and Hullar (2010), in a review published in Hearing Research, found that at frequencies around 5 Hz, the OHC could be stimulated at pressure levels up to 40 dB below those required to stimulate the inner hair cells — meaning the auditory pathway is not activated, but the ear still registers and responds to the signal.
Salt, A.N. & Hullar, T.E. (2010). "Responses of the ear to low frequency sounds, infrasound and wind turbines." Hearing Research, 268(1–2), 12–21. PMC2923251A 2007 study by Hensel et al. demonstrated that exposure to infrasound at 6 Hz altered cochlear processing as measured by distortion product otoacoustic emissions (DPOAEs) in normally hearing human subjects — direct evidence of inner-ear response to infrasound in humans.
Hensel, J., Scholz, G., Hurttig, U., & Janssen, T. (2007). "Impact of infrasound on the human cochlea." Hearing Research, 233(1–2), 67–76. PubMed 17761395Because the hair cells of the vestibular organs are most sensitive to frequencies below ~30 Hz, infrasonic exposure may register not as "sound" but as non-specific whole-body pressure, swaying sensations, or general discomfort — symptoms that can appear unrelated to any obvious acoustic source.
What symptoms have been documented?
A systematic review by Baliatsas et al. (2016) covering observational studies in the general population found associations between low-frequency noise and infrasound exposure and annoyance, sleep disturbance, headaches, dizziness, and difficulty concentrating, particularly from wind turbines and industrial plant. A 2026 study published in Frontiers in Behavioral Neuroscience found that infrasound exposure at near-threshold levels significantly increased salivary cortisol and negative affect scores in human subjects in a controlled setting, strengthening the case for a real physiological response.
Baliatsas, C., van Kamp, I., van Poll, R., et al. (2016). "Health effects from low-frequency noise and infrasound in the general population: is it time to listen?" Science of the Total Environment, 557–558, 163–169. Frontiers in Behavioral Neuroscience (2026). "Infrasound exposure is linked to aversive responding, negative appraisal, and elevated salivary cortisol in humans." doi:10.3389/fnbeh.2026.1729876A NIOSH Health Hazard Evaluation report (2019) also noted that infrasound at 95 dB at 5 Hz and 16 Hz affected body sway in a controlled study, consistent with vestibular disruption.
NIOSH HHE Report 2019-0119-3362. CDC/NIOSHImportant caveat: the research literature on infrasound and health is genuinely unsettled. Many studies report inconsistent vestibular effects, and evidence for physiological harm at typical ambient industrial levels (as opposed to very high experimental levels) remains actively debated. The hypothesis presented here is not established science — it is a testable framework.
02. The local context: Hammond, IN
Hammond is a heavily industrialized city on the southern shore of Lake Michigan, historically and currently home to multiple large manufacturing operations. Confirmed major industrial presences include Unilever's soap factory, Cargill's corn processing plant (at 1100 Indianapolis Blvd.), Atlas Tube, and Munster Steel, in addition to freight rail lines and expressways traversing the city.
Hammond, Indiana. Wikipedia. en.wikipedia.org/wiki/Hammond,_Indiana (confirmed industrial facilities; population from 2020 census)In January 2024, residents near the Cargill plant filed formal complaints about loud industrial noise that began around midnight. Hammond's head of Environmental Management, Ronald Novak, stated he had "never heard such a loud noise come out of a plant in the city of Hammond" in over 50 years of work. Mayor McDermott publicly put Cargill "on notice" at a community meeting. This confirms documented precedent for industrial noise affecting residential areas in Hammond.
NWI Times, February 2024. "Hammond Cargill plant put 'on notice' after residents complain of loud noise." nwitimes.comA geological note: soft lacustrine sediment
Hammond sits within the former bed of Lake Chicago, the precursor to Lake Michigan. Most of the city rests on sandy lacustrine sediment and former dune-and-swale terrain — confirmed by the city's own Wikipedia article — with a thin topsoil layer. Soft sediment transmits low-frequency ground-borne vibration more efficiently than bedrock, potentially allowing infrasound from heavy machinery and rail traffic to couple into building structures more readily than in geologically harder settings.
The Lake Michigan basin has also undergone glacial isostatic adjustment (GIA) since the retreat of the Laurentide Ice Sheet. Geodetic measurements indicate Lake Michigan is uplifting at approximately 0.9 mm/year. However, there is no established scientific basis for claiming that GIA stress amplifies industrial infrasound in a way that would be relevant at residential scales — that claim from the original document is not supported by the literature and is dropped here.
Sella, G.F., et al. (2002). "Glacial Isostatic Adjustment in the Great Lakes Region Inferred by Tide Gauges and Satellite Altimetry." American Geophysical Union abstract. Lake Michigan uplift rate: 0.9 mm/yr. ADS abstract Hammond geology: US Census Bureau / City of Hammond via Wikipedia, confirmed dune-and-swale lacustrine origin.03. The falsifiable hypothesis
- Acoustic measurement reveals no infrasound above background levels at affected residences.
- The infrasound signal is broadband and lacks identifiable tonal components, making phase-locked cancellation intractable.
- The ANC system achieves <6 dB reduction at the error microphone despite correct calibration.
- Symptom self-reports show no difference between active-ANC and sham-control conditions in a blinded trial.
- Symptoms correlate with timing of documented chemical emissions or other non-acoustic exposures rather than industrial noise schedules.
Why this approach is technically plausible
Active noise control (ANC) using phase-inverted anti-sound has been formally proposed and studied for infrasound from wind turbines. Baliatsas et al. (2018), published in Nonlinear Engineering, specifically proposed using arrays of loudspeakers driven with opposite-phase signals computed from reference microphone input to cancel infrasound in residential interiors, deriving transfer function equations for the system.
Baliatsas, C., et al. (2018). "Infra-sound cancellation and mitigation in wind turbines." Nonlinear Engineering, 7(1). De GruyterANC is particularly effective at low frequencies because the long wavelength of infrasound (a 5 Hz tone has a ~68m wavelength) allows a single cancellation speaker to create a meaningful "zone of quiet" within a room — unlike higher frequencies, where the small wavelength requires many precisely positioned speakers. This is why ANC is a standard technique for engine noise suppression and HVAC duct noise at low frequencies.
Principle of active noise cancellation via phase inversion
Known technical limitations to be honest about
ANC works well in constrained acoustic environments (ducts, headphones) and for tonal noise. Open residential spaces present harder challenges: the sound field is three-dimensional, reflections from walls create complex interference patterns, and if the source signal is not highly tonal or coherent, the adaptive filter cannot lock on. A 2020 study in Scientific Reports demonstrated up to 10 dB reduction in sound pressure level through an open window using an ANC array, but also found that attenuation in the low-frequency range was limited by loudspeaker physical size.
Lam, B., et al. (2020). "Active control of broadband sound through the open aperture of a full-sized domestic window." Scientific Reports. nature.comANC for infrasound in a residential interior is more feasible than most people assume, specifically because very long wavelengths mean you don't need a speaker array — a single well-placed subwoofer-class driver can influence the pressure field across a room. But success depends entirely on the noise being tonal (not broadband), which has to be verified by measurement first.
04. What needs to be measured
No amount of theoretical reasoning substitutes for actual measurement. The following steps would establish whether the hypothesis is worth pursuing, in order of cost and complexity.
Tier 1 — Baseline measurement
~$200–500
Raspberry Pi + MEMS barometric pressure sensor (e.g. Infineon DPS310, sensitive to infrasound) and a low-frequency microphone or geophone. Logs pressure fluctuations at 0–20 Hz. Correlate timestamps with industrial shift schedules. Determines whether measurable infrasound exists before any other investment.
Tier 2 — Characterization
~$1,000–5,000
Calibrated infrasound microphone (e.g. Earthworks M30 or a Brüel & Kjær Type 4193) with a proper data logger. Establishes accurate frequency and amplitude data. Required to tune any cancellation system and to demonstrate regulatory non-compliance if applicable.
Tier 3 — ANC pilot
~$500–3,000
Adaptive feedforward ANC system using a reference mic (outside), error mic (inside), a DSP board (e.g. miniDSP) running an LMS adaptive filter, and a high-excursion subwoofer. Measures reduction achieved. Requires Tier 2 data first to verify tonal frequencies exist.
05. Who can help
Purdue University Northwest — Hammond campus
Purdue Northwest has engineering and chemistry departments with instrumentation resources. Environmental monitoring or a senior capstone project on acoustic measurement is the kind of work faculty often welcome as a community-engaged research opportunity. The chemistry department can also help rule out chemical co-exposure as an alternative explanation for symptoms.
Lake County Health Department
filing a formal complaint with the Lake County Health Department is a documented first step under Indiana's regulatory structure. Multiple household complaints can trigger an official county-level environmental health assessment, with industrial hygienists who can conduct professional measurements. Indiana Code 36-1-3-8 governs noise ordinances, with industrial zones permitted up to 75–85 dB.
Indiana Department of Environmental Management (IDEM)
IDEM regulates air quality and environmental nuisance complaints. They have been documented applying for federal grants to address industrial environmental issues in Northwest Indiana. An infrasound complaint with documented data may qualify for EPA Environmental Justice grant funding.
Carolyn Boiarsky
Professor at Purdue Northwest with a background in environmental health communication and journalism. Potentially useful for translating technical findings to the public and to press if data warrants it.
06. Recommended next steps
- Document symptoms systematically: time of day, severity, weather, proximity to industrial shift changes and train schedules. A consistent temporal correlation with industrial activity is preliminary evidence worth having before any measurement.
- file a formal complaint with the Lake County Health Department. Multiple households filing independently increases the likelihood of triggering an official assessment.
- Deploy a Tier 1 sensor. A Raspberry Pi with a DPS310 or MPU-6050 (accelerometer) sensor costs under $50. Software to log infrasound is available open-source. This is the minimum viable experiment — it either finds something or eliminates the hypothesis cheaply.
- If Tier 1 data shows measurable infrasonic energy correlated with industrial activity, contact Purdue Northwest about a student research collaboration for Tier 2 calibrated measurement.
- If Tier 2 confirms tonal infrasound above ambient background, design a small ANC pilot as described above, with blinded symptom reporting as the primary outcome measure.
- If symptoms do not track industrial schedules, or if chemical odors are reported, prioritize air quality testing over acoustic investigation — IDEM is the appropriate agency.
Cited sources