Infrasound: The Noise You Feel But Can't Hear
Published on: January 12, 2026
Key Takeaways
A low-frequency hum is vibrating your house, but you can't hear it? We explain infrasound, Low Frequency Noise (LFN), and how to identify the source.
You feel a pressure in your ears. The windows rattle slightly. You can sense a vibration, but when you listen closely, you hear... nothing. You might be experiencing Infrasound or Low Frequency Noise (LFN). It's one of the most difficult noise complaints to prove, but also one of the most distressing.
What is Infrasound?
Human hearing typically ranges from 20 Hz to 20,000 Hz. Infrasound refers to sound waves below 20 Hz. While you can't "hear" these waves as a tone, you can feel them as vibration or pressure.
Low Frequency Noise (LFN) is slightly higher (20-100 Hz), like the deep rumble of a distant diesel engine. LFN travels incredible distances and passes easily through walls and windows that block higher-pitched sounds.
Common Sources of The Hum
If you are experiencing this, the culprit is likely large mechanical equipment, even if it's far away:
- Industrial HVAC: Large cooling towers on commercial buildings.
- Generators/Turbines: Power plants or wind turbines.
- Idling Trains/Trucks: Diesel engines idling miles away can create a resonance frequency that amplifies inside your home.
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Why It's Hard to Enforce
Most city noise ordinances use the dB(A) weighting scale, which is designed to mimic human hearing. It deliberately filters out low frequencies. An infrasound source might register as "quiet" on a standard A-weighted meter even if it is shaking your house.
The Solution: You need a measurement in dB(C) or dB(Z) (unweighted). These scales capture the low-end energy. If you are filing a complaint about vibration/humming, specifically request a "C-weighted" measurement.
The Takeaway
You aren't imagining it. Infrasound is real physics. To solve it, you must identify the mechanical source and advocate for noise measurements that capture low frequencies (C-weighting) rather than the standard A-weighted limits.
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