Oscillogram of a male bullfrog’s call recorded at site 1 in 1994. This particular call is made up of six individual notes or croaks. Arrows point to modulations or gaps seen in individual notes. The first note contains no modulations; notes two through six contain 1, 2, 3, 2, and 2 modulations, respectively. Time-domain waveform was exported from cooledit 2000.