On the music player, a plurality of vertical bars jump up and down from left to right with the music rhythm, showing the spectrum of the music player like a bar graph; The spectrogram shows the DB distribution from 20Hz to 20 Hz, which can be understood as loudness distribution, also known as volume. The waveform calculated by fft is sometimes spectral line, sometimes reduced horn power supply voltage signal waveform, and of course it can also be regarded as sound waveform.

As shown in the figure below, the instantaneous loudness of each frequency is displayed. The lower the frequency, the lower the left frequency, the higher the right frequency, and the middle is the alto.