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sound-hearing-2 · content 3 · setup format 1
What supports the explanation?
The Greenwood relationship approximates human organ-of-Corti frequency and position; it is distinct from a neural spiral-ganglion map.
Stakhovskaya et al. (2007), Frequency Map for the Human Cochlear Spiral Ganglion, restates Greenwood’s human coefficients and explicitly distinguishes the two anatomical maps. Greenwood (1990) is the original reference. Used for a reference marker only, not neural response prediction.
Hair-cell electrical responses lead to chemical transmission at the afferent synapse.
Ottersen et al., Molecular organization of a type of peripheral glutamate synapse (1998). The inner-hair-cell synapse and postsynaptic receptors support the distinction between transduction, transmitter release and nerve activity. No microscopic image is copied.
Voice production involves vibrating vocal folds and resonating air passages.
NIDCD, Taking Care of Your Voice, What is voice? and Use your voice wisely. Supports the source-to-air connection in the optional gentle observation; this adapted procedure has not been trialed with learners.
One-dimensional plane wave, no attenuation, reflections or three-dimensional spreading. Air markers are sample parcels, not a molecular-dynamics calculation.
The unfolded ear and magnified close-ups are functional schematics, not an anatomical section. The basilar-membrane place marker uses the approximate human Greenwood map; it is not a personal pitch map, an implant map or a cochlear fluid solver.
The animation shows an established continuous tone, not an onset/transit-time experiment. Ear-part motion and neural pulses are qualitative; the air wave alone uses the stated equation. The simulation is silent, with no loudness or medical assessment.
A reference map for the cochlea: Greenwood’s organ-of-Corti approximation uses f = 165.4 × (10^(2.1x) − 0.88), where x is fractional distance from the apex. The unfolded view reverses that coordinate so base is at the left. It is a reference relationship: anatomy varies, sound level affects responses, and the drawn motion envelope is illustrative.
Frequency and wavelength: For the chosen uniform medium, c = fλ. We fix c = 343 m/s as an illustrative air value near room temperature. Doubling frequency halves wavelength. Actual sound speed depends on the medium and conditions.
Displacement is not pressure: The visual uses ξ(x,t) = A cos(kx − ωt). Compression follows −∂ξ/∂x, giving a sine-shaped pressure variation a quarter cycle from displacement. Here k = 2π/λ and ω = 2πf. Particle displacement is magnified and playback is slowed 400×.
Amplitude is not a hearing test: The amplitude setting is a relative displacement scale, not decibels at your ear. Larger amplitude generally means greater sound intensity in the same linear medium. Perceived loudness and pitch involve the listener as well as the physical wave; no hearing threshold is estimated.
What has been checked
Analytical reference cases, conservation or transition invariants, finite drawing commands, bounded setup parsing, discovery and route integrity are checked automatically. These checks do not establish anatomical fidelity, learner outcomes or browser/device compatibility. Independent subject review, learner trials, comprehensive accessibility review and browser video encoding checks remain pending.
Each source supports the associated claim. Sources do not certify this implementation or its visuals.
About the cover illustration
The topic card uses an AI-generated editorial illustration. It introduces the subject; it is not a validated anatomical reference or a measured landscape. The experiment’s diagrams, readouts and assumptions explain the model separately.