An LTSA (long term spectral average) is essentially a spectrogram which shows particularly long time periods, e.g. hours, days or even months. They’re great for summarising passive acoustic studies, were acoustic data may have been collected over extended periods of time. This post is going to describe how to use PAMGuard (www.pamguard.org) , an open source tool kit for analysis to generate an LTSA. We’ll then import it into MATLAB and create a publishable figure.