. 2018 Apr 30;115(20):5193–5198. doi: 10.1073/pnas.1719291115

Table 1.

Acoustic indices used to compare pre- and postdegradation reef recordings

Acoustic index	Mechanism	Calculation method	Citations
Acoustic complexity index	Measures the variation in the intensity of changing frequencies over time.	The package Seewave (50) on R v3.3.0 (www.r-project.org).	Development: ref. 33
Acoustic complexity index		The package Seewave (50) on R v3.3.0 (www.r-project.org).	Previous use: refs. 24 and 51–54
Acoustic richness	Combines a previous Shannon–Weiner-based acoustic entropy index (55) with a rank-based incorporation of the median of the amplitude envelope.	The package Seewave (50) on R v3.3.0.	Development: ref. 34
Acoustic richness		The package Seewave (50) on R v3.3.0.	Previous use: ref. 54; similar Shannon–Weiner-based acoustic entropy indices used by refs. 51 and 55.
Snap rate	Counts the number of independent snap sounds occurring in 30 s, doubling this to achieve a per-minute value.	A custom-designed MATLAB (MathWorks, Inc.) algorithm detecting snap events (see Materials and Methods for details).	Development: Custom-designed.
Snap rate			Previous use: Similar algorithms used by refs. 51, 53, and 56–59.
Sound-pressure level	Measures the root-mean-squared amplitude level (dB re 1 µPa) across the full-frequency bandwidth (0.01–24 kHz) using a Hann window function (FFT size = 512).	The PAMGuide analysis package (38) on MATLAB.	Development: A simple measurement of sound intensity.
Sound-pressure level		The PAMGuide analysis package (38) on MATLAB.	Previous use: refs. 19, 24, 57, 59, and 60.