Audio Engineering

452 Chapter 15

few milliseconds of a musical signal we are very likely to observe a waveform that can
be seen to have an underlying structure ( Figure 15.8 ). Striking a single string can produce
a waveform that appears to have a relatively simple structure. The waveform resulting
from striking a chord is visually more complex, although, at any one time, a snapshot of
it will show the evidence of structure. From a mathematical or analytical viewpoint the
complicated waveform of real sounds is impossibly complex to handle and, instead, the
analytical, and indeed the descriptive, process depends on us understanding the principles

(a)

Time

Figure 15.8 : (a) An apparently simple noise, such as a single string on a guitar, produces

a complicated waveform, sensed in terms of pitch. The important part of this waveform

is the basic period of the waveform, its fundamental frequency. The smaller detail is

due to components of higher frequency and lower level. (b) An alternative description is

analysis into the major frequency components. If processing accuracy is adequate, then

the description in terms of amplitudes of harmonics (frequency domain) is identical to the

description in terms of amplitude and time (time domain).

(b)

500 1 kHz 1.5 2 kHz 2.5

Frequency H 3

3 kHz

0

dB

Amplitude of frequency component

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