Definitions for "Power spectrum"
The presentation of the square of the amplitudes of the harmonics of a time series as a function of the frequency of the harmonics.
a representation of a signal in the frequency domain
A power spectrum plot shows the relative levels of power at different frequencies. The example power spectrum plot discussed in the section on music and the ear shows that the power around 4 kHz is about 20 dB below (1% of) the power at the lowest frequencies, and power drops another 20 dB for frequencies above 12 kHz.