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Chapter 5. Sound > Understanding Sound

Understanding Sound

Although sound is invisible, tools exist to help us understand its physical representation. They show us that sound is made up of waves, which vary in length (to denote time) and size (to denote volume). When these sound waves reach our eardrums, they cause them to vibrate—thus hearing is born. We're able to distinguish among sounds because each one causes our eardrums to vibrate in a different fashion.

Analog sounds, or those we hear naturally, are produced by sound waves that our ears are designed to detect and process. Digital sampling—which transforms analog sound waves into mathematical equations—was invented to record, edit, and play back such sounds in a digital environment. Close examination of a digitally sampled sound reveals a bunch of vertical lines of varying length stacked closely together. Each of these lines represents a sample. The quality of a digital sound is determined by the number of samples that exist within each second of sound (the sampling rate) as well as the number of values each sample can contain (sample size) (Figure 5.1). For example, a 16-bit, 44.1-kHz sound contains 44,100 (44.1 kHz) lines, or samples, per second, each of which can have a value between 0 and 65,536 (16 bits). The result? A highly accurate digital sound, but also a large file. On the other hand, an 8-bit, 11.025-kHz sound contains only 11,025 samples per second, each of which can have a value between 0 and 255. The result here is a duller, less clear representation of the original sound—but also a much smaller file.


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