Question

How does an animal interpret the location of a sound?  

part of the brain is responsible for integrating this?

Answer 1

Sound localization is a listener's ability to identify the location or origin of a detected sound in direction and distance.A variety of sounds , with different qualities, hit the ear drum at the same time. Yet, humans as well as animals are able to isolate, identify and prioritize overlapping sounds. This is apparently universal to all animals and serves as a critical survival mechanism. Several researchers have worked on this and tried to understand how the mechanism works.

It has been found that birds are able to pick out separate sound sources faster than humans when they partially overlap and the ability to segregate the sounds becomes easier the more they are offset, highlighting the importance of timing in sound segregation.

It is now believed that sound localisation in mammals as well as other animals , by the auditory system, is done with the help of several cues like intensity difference between both ears, spectral information, timing analysis, correlation analysis and pattern matching. Animals have an extra localisation cue for sound localistion and that is ear movements.

Sound waves are mechanical vibrations travelling through a medium. When they stimulate the auditory nerves, the sensation is taken to the brain. In vertebrates, inter aural time difference is calculated in the superior olivary nucleus of the brain stem. Neurons in the superior olive accept innervation from each ear with different connecting axon lengths. Some cells are more directly connected to one ear than the other, thus they are specific for a particular inter aural time difference.

Neurons sensitive to inr aural level ifference are excited by stimulation of one ear and inhibited by stimulation of the other ear, such that the response magnitude depends on the relative strengths of the two inputs, which in turn depends on the sound intensities at the ears.

Since most animals have two ears, interaural time differences and interaural level differences play a key role for hearing in most animals. But , besides these the influences on localisation of these effects are also dependent on head size , ear distances , position of ears on the head and the orientation of ears. Since animals can move teir ears, it can be used as a lateral localisation cue by the animals. Head tilting by animals helps them to obtain rough elevation information of sound waves.

All the stimulation received by the auditory nerves are transmitted to the auditory cortex , located in the temporal lobes of the brain which are situated above the ears.