Brown Note Test — Myth Explained

The brown note is an urban legend about a 5 to 9 Hz infrasonic tone that supposedly causes involuntary defecation. This page plays sub-20 Hz sine tones with a cone-excursion readout, showing why small speakers cannot reproduce the fundamental and what extreme low frequency really does. Nothing is uploaded.

How to use it

1. Pick a frequency. Buttons select 5, 7, 9, 12, 16, 20 or 30 Hz; the 7 Hz button is marked as the mythical brown note and selected by default.
2. Set the output level. The slider runs from 5 to 50 percent and defaults to 25 percent; the engine caps gain at 0.5 to limit cone excursion.
3. Press Play Sub-Bass Sine. One sine oscillator runs at the chosen frequency; Stop fades it out over 30 ms.
4. Read the excursion multiplier. The readout compares cone displacement with a 40 Hz reference using (40 / f)^2: 32.7 times the excursion at 7 Hz, 64 times at 5 Hz.
5. Read the preset description: 16 Hz is the 32-foot organ C, 20 Hz the nominal lower hearing limit, and 30 Hz usable sub-bass.
6. Check the science cards on the MythBusters trial, equal-loudness thresholds, organ resonance and extreme infrasound.
7. Stop when the speaker starts rattling. Buzz and rattle are the driver’s own distortion, not the tone you asked for.

Why 7 Hz cannot come out of a laptop

A 7 Hz tone has a wavelength of 49 metres in air at 20 °C, because wavelength equals 343 divided by frequency.

Reproducing low frequencies costs displacement. For a constant SPL well below a driver’s resonance, cone excursion scales as 1/f^2: a speaker that moves 1 mm at 40 Hz needs about 33 mm at 7 Hz. Laptop drivers and earbuds have 1 to 3 mm of usable travel, so the coil runs out of excursion long before the tone is audible. What you hear instead is harmonic distortion from the nonlinear suspension at 14, 21, 28 Hz and beyond, plus cabinet rattles.

Hearing thresholds make it worse. Sensitivity falls steeply below 20 Hz, and published infrasound thresholds at single-digit frequencies sit above 100 dB SPL, so a 0 dBFS sine at 7 Hz produces almost no audible fundamental through small speakers. Keep the scales separate: dBFS is the digital signal, dB SPL is air pressure, and the slider controls the first, not the second.

Brown note versus brown noise

The presets here are sine tones, not brown noise, and the two are often confused.

Brown noise is a broadband spectrum whose power spectral density falls as 1/f^2, about -6 dB per octave, concentrating energy in the lowest octaves. It is named after Brownian motion, not a colour. The brown note is a single-frequency legend whose name is a pun on the expected outcome.

Preset	Category	Wavelength at 20 °C	Excursion vs 40 Hz	Notes
5 Hz	Infrasound	68.6 m	64.0x	Deepest option, far below hearing
7 Hz	Infrasound, mythical	49.0 m	32.7x	The legendary brown note
9 Hz	Infrasound	38.1 m	19.8x	Felt only at extreme levels
12 Hz	Infrasound	28.6 m	11.1x	Felt as flutter rather than pitch
16 Hz	Infrasound	21.4 m	6.3x	32-foot organ C, very high threshold
20 Hz	Hearing boundary	17.2 m	4.0x	Nominal lower limit of hearing
30 Hz	Sub-bass	11.4 m	1.8x	Reproducible on capable systems

What the evidence says about the myth

The story probably began with Cold War-era vibration testing, where subjects were mechanically coupled to shaking seats rather than exposed to airborne sound; levels around 2 to 3 Hz at 160 dB produced nausea, visual disturbance and loss of coordination. Those conditions are not reproducible with a loudspeaker in air, an inefficient way to transfer low-frequency vibration into a body.

The best-known public test is the 2005 MythBusters trial, which used twelve modified Meyer Sound 700-HP subwoofers. The rig reached about 120 dB SPL at 9 Hz and roughly 153 dB above 20 Hz; participants reported anxiety and shortness of breath but no loss of bowel control, and the show declared the myth busted. Very high airborne infrasound can cause vestibular discomfort, nausea and chest pressure in occupational settings, but no frequency has been shown to trigger involuntary defecation. This page makes no claims about digestion or any other bodily effect.

Accuracy, limits and troubleshooting

• The excursion figure is arithmetic against a 40 Hz reference, not a measurement of your hardware; real drivers add suspension nonlinearity, port behaviour and thermal limits.
• The level slider controls digital gain, so a 5 Hz fundamental may be inaudible even at 50 percent. Phone and laptop speakers roll off below a few hundred hertz, most headphones below 30 to 40 Hz, and even good subwoofers struggle below 20 Hz.
• Clicks, pops and rattles are distortion products and mechanical noise; if a driver sounds stressed, stop. Sustained low-frequency content at high level is hard on small drivers and on hearing: voice coils heat up, suspensions can over-travel, and bass adds to overall exposure.
• Do not use this page to find your system’s maximum level at 5 to 10 Hz: excursion is worst there, and protection circuits are not designed for slow sub-10 Hz signals.
• Windows enhancements, macOS loudness EQ and Bluetooth codecs change the bass you hear; disable them when comparing devices.
• This is an educational demo, not a hearing test or medical device. If you are concerned about your hearing, see an audiologist; for a controlled low-frequency sweep, use the low-frequency hearing test at a modest level.

Related tools

• Subwoofer Test — check what your system can genuinely reproduce from 20 to 200 Hz.
• Low-Frequency Hearing Test — map your own thresholds from 10 to 100 Hz at a safe level.
• Noise Generator — hear brown noise as a broadband spectrum rather than a single sine.