The acoustic signatures of many animals contain features we humans cannot appreciate, given the limited range of frequencies we can hear. In fluid dynamics and many other fields, scientists and engineers have to find ways to analyze and decompose time-series data–like acoustic pressure signals–into useful quantities. Mark Fischer uses one tool for such analysis, a wavelet transform, to turn the calls of whales, birds, and insects into the colorful snapshots seen here. Wavelet transforms are somewhat similar to Fourier transforms but represent a signal with a series of wavelets rather than sinusoids. They’re also widely used for data compression. (Image credits: M. Fischer/Aguasonic Acoustics; via DailyMail)