Infrasound Sensation Linked to Cochlear Potentials

A new study published in *Scientific Reports* provides direct evidence that the human cochlea generates electrical potentials in response to sounds far below the range of hearing. This discovery, from researchers Carlos Jurado and Torsten Marquardt, identifies a physiological mechanism for infrasound sensation.

Measuring the Inner Ear’s Response to Silent Sound

Researchers have long debated whether humans can sense infrasound—sound waves with frequencies below 20 Hz, the typical limit of human hearing. People report feelings of pressure, unease, or even dizziness in environments rich in low-frequency noise, such as near wind turbines or large industrial machinery. Until now, evidence for a direct physiological mechanism in the cochlea has been limited.

The team, with Jurado from the Norwegian University of Science and Technology and Marquardt from the UCL Ear Institute, designed an experiment to capture the inner ear’s electrical response to these very low frequencies. They used a method called electrocochleography, which records tiny voltage changes in the ear. Participants were exposed to pure tones at 8 Hz and 12 Hz, levels considered “inaudible,” while researchers measured the resulting cochlear microphonic potential from the ear canal.

Infrasound Generates a Clear Cochlear Signal

The study’s results were clear. The data showed a “significant increase” in the recorded electrical signal specifically during the infrasound stimulation periods compared to baseline silence. This cochlear microphonic potential is a direct electrical copy of the sound wave, generated by hair cell activity in the inner ear. The fact that it was detected for 8 Hz and 12 Hz tones proves that the cochlea’s sensory apparatus is activated by these frequencies, even if they do not lead to a conscious auditory perception.

This finding moves the discussion beyond subjective reports. It provides an objective, measurable biomarker that the inner ear is processing infrasound. As the authors state in their paper (DOI: 10.1038/s41598-026-50179-w), this demonstrates that “infrasound sensation is mediated by intracochlear electrical potentials.”

Implications for Tinnitus and Sound Sensitivity Disorders

This discovery has important implications for understanding hearing health. For individuals with conditions like tinnitus (phantom ringing) or hyperacusis (oversensitivity to sound), chronic exposure to environmental infrasound could be a previously overlooked factor. If the cochlea is constantly generating electrical activity in response to a low-frequency hum that the brain cannot properly identify, it might contribute to neural confusion or stress on the auditory system.

The research may also inform our understanding of differences in brain responses to sound seen in conditions like misophonia and hyperacusis. An abnormal or heightened cochlear response to low frequencies could be an initial trigger for downstream neural reactions. Furthermore, understanding the cochlea’s full response range could influence therapies aimed at calming the auditory system, such as generative music for sensory sensitivities.

A New Tool for Diagnosis and Research

Practically, this work provides audiologists and researchers with a new tool. Recording the infrasound cochlear microphonic could become part of a diagnostic battery to assess the complete functional state of the inner ear. It opens a new avenue to objectively study the effects of low-frequency noise exposure in occupational, environmental, and clinical settings.

The finding also connects to broader neural research. If the inner ear sends these low-frequency signals to the brain, how are they processed in areas like the cerebellum or other brain networks involved in hearing disorders? Future studies can now trace this pathway from a confirmed peripheral origin.

The work by Jurado and Marquardt changes a fundamental understanding of human hearing limits. It confirms that our hearing system monitors a wider sonic world than we consciously perceive, with potential consequences for long-term auditory health and disorder management.