5.
The oscilloscope shows electronic translations of the compressions and rarefactions of sound
waves, and the various parts of these waves can be examined by using the sine wave (a representation of
a pure tone) as an example. The following information will explain the characteristics of a sound wave
which also constitutes the parts of a sine wave.
Learning Event 2:
MEASUREMENT CHARACTERISTICS OF SOUND WAVES
1.
Definitions of Sound Wave Characteristics:
a. Frequency denotes the first characteristic of sound and a part of a sine wave. The frequency
of a wave equals the complete number of cycles occuring in one second of time. One complete cycle
starts at one point on a wave and traces to the next same point further on down, or from 0 degrees to 360
degrees (fig 1-8).
Figure 1-8. Sine waves
(1) For example, from 1 to 1a equals one complete cycle or from 2 to 2a equals one complete
cycle. The frequency of a wave equals the number of complete cycles per second (CPS) or Hertz (Hz).
Scientists derived the term "Hertz" in honor of a German scientist who worked in electromagnetic
theory in the 18th century. When talking about the frequency of a wave, we use the terms Hertz (Hz)
and cycles per second (cps) interchangeably.
(2) The audio spectrum (or the range of frequencies humans can hear) consists of frequencies
from 15 Hz to 20,000 Hz.
b. Wavelength denotes the second characteristic of sound and another part of a sine wave. All
sound waves, regardless of their length, go from 0 degrees to 360 degrees in one complete cycle. The
amount of distance from 0 degrees to 360 degrees when plotted as a sine wave determines the length of
the wave or wavelength. Wavelength depends on the frequency. The higher the frequency, the greater
the number of cycles per second. The greater number of cycles per second requires a shorter distance
from 0 degrees to 360 degrees for one complete cycle. This in turn produces a shorter wavelength (fig
1-9).
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