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1.2 Who Makes Music? 1.2.1 Sound From Nature: Why Animal Communication Stands Out Against Random Natural Noise
When you listen to sounds from nature such as the wind in the trees or water rushing in a stream, what do you hear? Random and diffuse background sound. Like traffic in the city. A wide range of frequencies all mixed together. (Frequency just means number of vibrations per second. A given frequency number corresponds to a particular tone or note, such as A-440, the A above Middle C. More on this in Chapter 3.)
Animal communication evolved as ways for animals to signal each other using calls that focus on narrow bands of frequencies. Energy concentrated in this way results in sounds that carry long distances. You can hear the hootin’ and howlin’ easily against the random background sound.
Species also evolve sounds specific to their own kind, so that they can identify each other. In a tropical rainforest, for example, a small area of, say, one square kilometer may contain scores of different bird species. Each species has evolved a signature sound, a distinctive song or repertoire of songs. (More on developing a signature sound in Chapter 11.)