A sound frequency of 19 Hertz (Hz) is a very low-pitched sound wave, at the extreme lower end of the sound spectrum. Most humans cannot distinctly hear this frequency. However, 19 Hz has garnered attention due to its potential for non-auditory effects. This article explores the nature of such low frequencies and what scientific understanding suggests about their impact on human well-being.
Understanding Infrasound
The 19 Hz frequency falls within infrasound, which includes sound waves below 20 Hz. These sounds have long wavelengths, allowing them to travel considerable distances with minimal energy loss. They can also penetrate various materials and structures, making them pervasive. Their low atmospheric absorption allows them to propagate globally, even diffracting around obstacles.
Infrasound originates from both natural and human-made sources. Natural occurrences include earthquakes, volcanic eruptions, ocean waves, avalanches, and large weather systems like storms or tornadoes. Human-made sources include heavy machinery, large vehicles, industrial processes, sonic booms, large explosions, and certain wind turbines. These low-frequency waves are a constant, though often unnoticed, part of many environments.
Human Perception and Responses
While 19 Hz is generally too low for the human ear to perceive as a distinct tone, it can be experienced through other bodily sensations. People might describe feeling it as pressure, vibration, or a subtle sense of unease. As frequency decreases, human hearing becomes less sensitive, requiring a sufficiently high sound pressure level for perception. At higher intensities, infrasound vibrations can be felt in various parts of the body.
Anecdotal reports have linked infrasound, particularly around 19 Hz, to the “brown note,” a fictional frequency purported to cause involuntary bodily functions. Scientific research has not substantiated such claims; the concept remains a myth. Reported physiological and psychological effects are typically much milder and highly subjective, varying greatly among individuals. These can include ear pressure, mild disorientation, fatigue with prolonged exposure, or a sense of anxiety or discomfort.
Scientific Consensus on Danger
Addressing whether 19 Hz is dangerous requires distinguishing between discomfort and verifiable physical harm. Scientific studies and expert consensus indicate that typical environmental or industrial exposures to 19 Hz do not pose a significant danger to human health. High-intensity infrasound, at very high decibel levels, could potentially have adverse effects, but these scenarios are rare and usually associated with controlled laboratory settings or extreme natural events.
Research has explored the impact of infrasound from sources like wind turbines. These studies often find that while some individuals report annoyance or sleep disturbance, there is no widespread scientific consensus pointing to serious, long-term health detriments at typical exposure levels. Perceived effects, such as pressure or vibration, are generally considered discomfort rather than direct physiological damage. While some research on low-frequency noise suggests links to stress, sleep disorders, or annoyance, these findings are often for general low-frequency noise and not specifically 19 Hz. Current scientific understanding does not support the idea that 19 Hz at commonly encountered levels poses a significant health danger.