Binaural Loudness

Abstract

The human auditory system is binaural, that is, it consists of two ears that are positioned on the two sides of the head. In a normally functioning system, acoustical pressure waves are picked up by the eardrums at the end of each ear canal. The pressure variations cause the eardrums to vibrate, and the bones of the middle ear transmit the vibrations to the liquid-filled cochlea in the inner ear. The cochlea converts the vibrations into electrical signals that are sent via the auditory nerve fibers to the cochlear nuclei. The nerve signals from the two ears are combined in the superior olivary complex and higher up in the auditory pathways. The brain then utilizes information at the auditory cortices on both sides in forming auditory percepts, such as loudness. Any malfunctioning or individual differences on either side may affect the transduction of pressure waves in the surrounding medium to auditory percepts in the brain, be it peculiarities in the shape of the torso, head, and pinnae, or differences in the peripheral or central auditory pathways (for a review of the physiology of hearing, see Pickles 2008).