The horizontal scale at the bottom indicates the different frequencies. The low frequencies (e.g. the hum of an engine) are located on the far left, the high sounds (e.g. the twitter of a bird) on the far right.

The vertical scale indicates the loudness level of the respective frequency, from soft (top) to loud (bottom). Values are given in decibels, abbreviated as dB. The healthy human ear begins to perceive sounds starting at 0 dB and reaches the threshold of pain at 110 dB.