Abstract
The second part of the current project was already planned and conducted before the findings of part one had become clear. The design of this second part was, therefore, not adjusted based on the uncertainties resulting from the first part of the study and followed exactly the same protocol and procedures. The target of the second part was to explore kurtosis as an acoustic parameter that could objectively describe sound conditions in a single unit that would capture those features that determine acoustic responsiveness in aquatic animals. Kurtosis is a statistical measure that is used to describe a sample or data distribution and is a measure of how long and far the tails are relative to the rest of the distribution. In order to collect data on the potential validity of kurtosis as an acoustic responsiveness measure, we tested variability 4 Leiden University in response level to variation in sound energy distribution in terms of 1) pulse rate and 2) signal-to-noise level (expressed as crest factor) by exposing fish to pulses of brown noise spectra of three different levels against two levels of elevated ambient noise.