The human brain extracts several kinds of information from the components of sounds: pitch, loudness, timbre, location and direction of movement.  Animal communication begins with sounds that declare specific meanings such as the alarm cries of squirrels and monkeys, bird songs that regulate mating and social activity and human grunts, shouts and cries that attract attention, signal danger and express emotion. 

Everyone who has spent time in natural environments will know that little sounds are ubiquitous in nature. Loud sounds are unusual and signal danger. Detecting and localizing the source of sounds is important to survival. Natural sounds are well defined and specific so that the identity of the source is quickly recognized.

A nature person will be able identify birds, insects, and other animals by their characteristic sounds. Wind sounds inform about weather changes. Some trees can be identified by the sounds of their leaves vibrating in the wind. A sailor can determine wind direction and velocity by moving his head slightly to hear changes in pitch and timbre as the wind blows around his head.

Our brains have evolved to detect and evaluate discrete low volume sounds.  When different birds are singing we tend to focus on one song. We habituate to regularly recurring sounds, tuning them out in favor of detecting novel sounds. The study of natural sounds and the innate tendencies of our mind provides a foundation for understanding music on the one hand and noise on the other.

The centre pitch frequency for human speech and singing is 440 Hertz, the A above middle C on the piano. Higher frequency components of sounds are harmonics that determine the timbral characteristics of the sound. The syntax of animal sounds is contained in rhythmic sequences of pitch and timbral changes. The sound production and reception systems in the temporal lobes of animal brains are hundreds of millions of years old and the latest developments are evolved modifications and elaborations of  old circuits.