For the millions of people living near wind farms, highways, or industrial facilities who report mysterious low-frequency discomfort — often dismissed by clinicians — this research offers a credible physiological explanation. Understanding how frequencies below 16 Hz are actually perceived reframes infrasound sensitivity from a psychosomatic puzzle into a measurable cochlear phenomenon.
Using non-invasive human measurements, the investigators demonstrated that at infrasound frequencies, the mechanical velocity of incoming sound waves drops so dramatically that the conventional inner hair cell (IHC) pathway — which relies on velocity-coupled stimulation — becomes largely inactive. Instead, displacement-coupled outer hair cells (OHCs) take over. Rather than triggering the auditory nerve mechanically, OHCs generate electrical potentials that act directly on the IHC membrane, inducing synaptic release and ultimately producing auditory sensation through an unconventional route. This dual-pathway model accounts for two perceptually distinctive infrasound features: an unusually shallow threshold slope below 16 Hz and a steep, rapid loudness growth with only modest increases in sound pressure level.
The cochlea has long been modeled as a frequency-selective mechanical transducer, so discovering that its cellular components engage in a functionally different electrical coupling at the very low end of the spectrum is genuinely novel. Prior hypotheses placed infrasound perception largely in the vestibular system or dismissed it outright. This electrical OHC-to-IHC mechanism is more specific and testable. That said, the study is human-cohort but relies on non-invasive proxy measures rather than direct intracochlear electrophysiology, meaning the proposed model is biophysically plausible rather than directly proven. Replication with electrocochleography or animal preparations with controlled OHC lesions would strengthen causal claims. Still, for a field where perception without mechanical IHC activation was largely theoretical, this is a meaningful step — potentially paradigm-shifting for low-frequency noise research and clinical audiology.