Page 39 - Master Handbook of Acoustics
P. 39
energy is too high for the eye to perceive. Nor can we see far-infrared light because its frequency is
too low. There are likewise sounds that are too low (infrasound) and sounds that are too high
(ultrasound) in frequency for the ear to hear.
Figure 1-13 shows several waveforms that typify the infinite number of different waveforms
commonly encountered in audio. These waveforms have been captured from an oscilloscope. To the
right of each capture is the spectrum of that particular signal. The spectrum shows how the energy of
the signal is distributed in frequency. In all but the signal of Fig. 1-13D, the audible range of the
spectrum was processed with a waveform analyzer having a very sharp filter with a passband 5 Hz
wide. In this way, concentrations of energy were located and measured.
