Handbook for Sound Engineers

30 Chapter 2

incident and reflected wave (many thousands of
meters). At radio frequencies, reflected waves pose a
huge problem, and cables are normally terminated
(operated into a matched impedance) to absorb the inci-
dent wave at the receiving device and reduce the level
of the reflection. The same is true for digital signals due
to their very high frequency content.

2.7 Superposition

Sine waves and cosine waves are periodic and singular

in frequency. These simple waveforms are the building

blocks of the complex waveforms that we listen to

every day. The amplitude of a sine wave can be

displayed as a function of time or as a function of phase

rotation, Fig. 2-14. The sine wave will serve as an

example for the following discussion about superposi-

tion. Once the size (wavelength) of a wave is known, it

is useful to subdivide it into smaller increments for the

purpose of tracking its progression through a cycle or

comparing its progression with that of another wave.

Since the sine wave describes a cyclic (circular) event,

one full cycle is represented by 360°, at which point the

wave repeats.

When multiple sound pressure waves pass by a point

of observation, their responses sum to form a composite

wave. The composite wave is the complex combination

of two or more individual waves. The amplitude of the

Figure 2-10. Acoustic wavelengths are relatively short and
interact dramatically with their environment. Audio wave-
lengths are extremely long, and phase interaction on audio
cables is not usually of concern. Courtesy Syn-Aud-Con.

Figure 2-11. Sound diffracts around objects that are small
relative to the length of the sound wave. Courtesy
Syn-Aud-Con.

Figure 2-12. Sound waves will interact with a large bound-

ary in a complex way. Courtesy Syn-Aud-Con.

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