"Waveform" figure showing a male bullfrog mating call

A figure known as a "waveform" showing a male bullfrog's mating call. On the x-axis is time in seconds; the y-axis shows sound pressure, or "loudness." This waveform was recorded in the field by an Automated Recording Unit that was deployed to monitor bullfrog invasions in the Pacific Northwest. The unique characteristics of bullfrog mating call waveforms were used as input for a computer program that can predict the likelihood that an audio recording contains a bullfrog call.