Any measurement recorded over time is a signal, which may be analyzed using various methods. Such an analysis can aid in understanding the physics underlying what was measured. The analysis is generally made in the time and/or frequency domains. The time domain corresponds to a waveform representation, which is useful for determining the exact times at which events, such as string plucks, occur. A frequency domain analysis is more useful for determining how much energy is present in a sound at various frequencies. For perfectly periodic sounds, the Fourier Series may be used to perform a frequency domain analysis. A Fourier Series demonstration applet may help provide you with some intuition behind using the Fourier Series to construct perfectly periodic sounds. Since the components in a Fourier Series are harmonic, they form a harmonic series.
