Vertical scale: frequency (0-4000 hertz); horizontal scale: time (1 frame aprox. equal to 2 seconds); color: signal strength (from lowest to highest, violet, blue, green, yellow, orange, red).
The above example of pup howling comes from a three-month-old pup
that has just heard an adult howling near the den site. Notice how its howls
are shorter in duration and higher in pitch, a consequence of its small overall
size and lung capacity. The howls do have the same modulated structure as the
adult lonesome howl, and serve the same role as contact calls.