Psychoacoustics

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Outer Ear

Only part visible from the outside, composed of the pinna with the temporal bone as foundation. Sound pressure waves are directed through the auditory canal towards the tympanic membrane.

Main function: reduces the abruptness of the pressure waves and protects the core ear functions.

Middle Ear

The tympanic membrane's vibration is detected and transmitted by the malleus through the incus to the stapes to be further transmitted to the inner ear. This is a purely mechanical process to concentrate the pressure wave where each of the three components are miniscule bone structures. The foot of the stapes is known as the oval window, of which the area is much smaller than the tympanic membrane.

The connecting eustachian tube opens to equalises the pressure behind the tympanic membrane with the pressure outside.

Main function: concentrates and transmits the pressure waves.

Inner Ear

The concentrated pressure waves are transmitted to the semi-circular canals and the snail-shaped cochlea, both connected to the brain by nerves. The cochlea is filled with liquid and cilia which vibrate.

Main function: interprets and converts the pressure wave into nerve signals to be sent to the brain.


Binaural Localisation

Sound source localisation by the difference in time in each ear.

Signals in Noise

Interpretation of selected signal despite ongoing background noise or disruption.

Decomposition into Pure Tones and Harmonics

Ability to distinguish between different frequencies.

Masking

When one signal's pressure is much higher than another, the lower is masked and may be absent in either the ear mechanics or the brain interpretation.

Critical Bands

The resolution of the frequency decomposition is the critical band, which is different for each frequency. At low frequencies of 40Hz, any signal within 5Hz may not be distinguished. But at a frequency of 500Hz, any signal with a difference of above 2Hz might be able to be distinguishable as separate signals.

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