Sound

Perception

Sound

pressure wave, vibration of molecules of the medium

Loudness

decibles (dB), sound amplitude and pressure level

Pitch

frequency (Hz), sound occilation rate, metameric

Chroma

sounds separated by an octave perceived as similar

Timbre

differences between sounds, multidimensional

Outer ear

pinna, cocha,

gather sound energy and focus it via the auditory meatus,

selectively filter sound frequencies

Middle ear

3 ossicles: Malleus, incus and stapes

impedance matching (match low impedance sounds to higher impedance fluid),

amplifies sound for inner ear

Inner ear

cochlea,

pressure waves —> neural signals

Cochlea

fluid filled, coiled, three chambers,

auditory transduction

Organ of Corti

in the cochlea,

runs along the basilar membrane,

inner and outer haircells, tectorial membrane,

start of auditory nerve

Inner hair cells

send info to higher cerebral levels,

transduction

Outer hair cells

receive projections from upper cerebral levels,

active filtering,

amplify and sharpen sounds

Mechano-electrical transduction

mechanical tension opens up potassium channels —> action potentials

Auditory nerve

The nerve that conveys signals from the hair cells in the organ of Corti to the brain;

made up of Type I and Type II auditory nerve fibers bundled together.

Basilar Membrane

tapered membrane suspended between the walls of the cochlea; thicker, narrower, and stiffer at the base than at the apex.

Frequency decompisition

high frequencies at base,

low frequencies at apex

Place model

zone of max excitation on the basilar membrane,

different hairs respond to different frequencies

Rate model

precise timing of individual spikes