The idea of a sound capable of forcing involuntary bowel movements has persisted in popular culture for decades, often referred to as the “Brown Note.” This concept suggests a specific sonic frequency exists that can cause physical chaos within the human body. The myth has been perpetuated through anecdotal stories and media portrayals, capturing the public imagination. To determine the validity of this claim, it is necessary to examine the physical properties of ultra-low frequency sound and compare the alleged effects to verifiable biological responses.
Defining the “Brown Note” Myth
The “Brown Note” refers to a hypothetical, ultra-low frequency tone, typically cited in the range of 5 to 9 Hertz (Hz), that is believed to trigger immediate and uncontrollable defecation. Proponents claim this particular frequency causes the human digestive system to enter a state of acoustic resonance. The resulting vibrations supposedly amplify within the intestines, leading to a complete loss of bowel control. The concept gained widespread recognition after being featured in the animated series South Park and was later investigated by the television program MythBusters. This specific claim serves as the focus of the investigation.
Infrasound: The Physics of Ultra-Low Frequencies
The specific frequency range associated with the myth falls squarely into the physical domain of infrasound. Infrasound is defined as sound waves with frequencies below 20 Hz, which is the lower limit of standard human hearing. These waves are not perceived by the ear as audible tones but are instead experienced as physical vibrations or pressure changes.
A variety of sources, both natural and artificial, constantly generate infrasound. Natural occurrences include earthquakes, volcanoes, avalanches, and severe weather patterns. Man-made sources range from heavy machinery and industrial fans to large wind turbines and the wake created by high-speed vehicles. The physical properties of these waves, characterized by long wavelengths, allow them to travel great distances and penetrate many physical barriers with minimal loss of intensity.
Documented Physiological Effects of Infrasound
While the specific alleged effect of the “Brown Note” is unsupported, high-intensity infrasound does produce verifiable physiological responses in the human body. Exposure to very high sound pressure levels, typically exceeding 120 decibels (dB), can induce a range of sensations. These reactions often include feelings of anxiety, general discomfort, and a sense of unease or dread, which are reported even when the sound is technically inaudible.
Research into the effects of low-frequency mechanical vibration, such as tests conducted by the U.S. space program, used high levels of 160 dB at frequencies like 2–3 Hz. Subjects in these studies, where vibration was mechanically coupled to the body, reported symptoms such as nausea, visual disturbances, and difficulties with motor control. High-level infrasound can also cause the chest cavity to resonate, leading to shortness of breath. The intensity, or amplitude, of the sound wave is a far greater determinant of biological effect than the frequency alone.
The Scientific Consensus on the Alleged Effect
Scientific investigation has consistently failed to find credible evidence supporting the existence of an infrasound frequency that causes involuntary defecation. The primary issue lies in the inefficiency of air as a medium for transferring the necessary energy from a sound source to the internal organs. For a sound wave to cause the bowels to resonate strongly enough to overcome the body’s muscular control, it would require an immensely high sound pressure level.
The widely publicized MythBusters test used specialized equipment to generate sound waves as low as 5 Hz and up to 120 dB at 9 Hz, finding no evidence of the claimed effect. Test subjects reported only mild physical anxiety and nausea, which was more likely due to the physical movement of air near the lungs than any specific gastrointestinal resonance. Achieving the necessary internal organ vibration via airborne sound would require power levels so high that they would likely cause catastrophic damage to the eardrums and lungs long before affecting the bowels. Ultimately, the “Brown Note” remains a persistent urban legend, definitively debunked by repeatable experiments and the physics of sound transmission through air.