Topic 6: Hearing — sound waves and pitch

Amplitude

The physical height or magnitude of a wave from its resting baseline to its peak, reflecting acoustic energy and determining the perceived intensity of sound.

Loudness

The subjective psychological perception of sound intensity, primarily determined by the physical energy and wave height of an acoustic signal.

Volume method (hearing)

A psychophysical measurement technique that systematically alters sound intensity levels to identify the absolute threshold at which an individual can detect acoustic stimuli.

Frequency

The rate of complete wave oscillations passing a fixed point per unit of time, quantified in hertz ($\text{Hz}$), which dictates how high or low a tone sounds.

Pitch

The subjective tonal experience of highness or lowness produced by an acoustic signal, directly governed by the physical cycle speed of vibrations.

Pitch perception

The sensory and cognitive processing through which the auditory system decodes vibrational cycle rates into an internal psychological experience of tonal height.

Wavelength (sound)

The spatial distance between two consecutive identical points, such as from crest to crest or compression to compression, in a traveling acoustic pressure wave.

Auditory canal

The external tubular passage through which acoustic pressure waves travel inward from the pinna to reach the tympanic membrane.

Eardrum (Tympanic membrane)

The thin, taut membrane separating the outer and middle ear that vibrates in mechanical response to arriving sound waves.

Ossicles

The trio of tiny middle-ear bones (malleus, incus, and stapes) that mechanically amplify and transfer vibrations from the tympanic membrane to the oval window.

Cochlea

The fluid-filled, coiled inner-ear structure containing sensory receptor hair cells that transduces acoustic fluid vibrations into electrochemical nerve signals.

Basilar membrane

The flexible, elongated tissue within the inner ear that vibrates differentially to fluid waves and physically supports the sensory hair cells.

Auditory nerve

The sensory neural pathway (cranial nerve VIII) carrying electrochemically transduced hearing signals from inner-ear hair cells to the brainstem and cortex.

Place theory

The pitch perception model asserting that perceived tone is determined by the specific anatomical location of peak vibration along the basilar membrane, primarily explaining high-frequency sound processing.

Frequency theory

The pitch perception model suggesting that sensory nerve fibers fire at a rate matching the exact oscillation speed of the acoustic wave, primarily explaining the sensation of low tones up to roughly $1000\,\text{Hz}$.

Volley theory

The auditory principle proposing that groups of neurons alternate firing in coordinated bursts to represent wave oscillations too rapid for any individual nerve cell to follow alone.

Sound localization

The perceptual process of identifying the spatial direction and position of an acoustic source by comparing interaural differences in arrival timing and sound level between both ears.

conduction deafness

Hearing loss caused by problems transmitting sound vibrations through the outer or middle ear.

sensorineural deafness

Hearing loss caused by damage to the cochlea's hair cells, the auditory nerve, or other parts of the inner-ear neural pathway.