The package seewave (Sueur et al. 2008) version 1.7.0 introduced the function ACI() to calculate the Acoustic Complexity Index (ACI). By then I was working on the last tests of my version of a function that would also calculate the ACI. So, I decided to keep my version in soundecology and let the community choose which version worked best for them.
The results of the functions do not match between the packages. I have received this question a few times, so I thought best to write a brief document about it since more people may wonder the same. After some tests, it seems that the differences are due to different assumptions or default values. The only way I can get the functions of both packages to agree was to set nbwindows in ACI() to a comparable value (duration of the file in seconds/seconds in each clump):
library(seewave) library(soundecology) data(tropicalsound) duration <- length([email protected])/[email protected] # 20 seconds duration
##  20
##  659.6697
acoustic_complexity(tropicalsound) # j is set to 5 by default
## ## max_freq not set, using value of: 11025 ## ## ## min_freq not set, using value of: 0 ## ## ## This is a mono file. ## ## Calculating index. Please wait... ## ## Acoustic Complexity Index (total): 660.088
I also tried with a 50 second-long file (not included in this vignette):
sound1<-readWave("LINE_2003-10-30_20_00_34.wav") duration <- length([email protected])/[email protected] # 50 seconds ACI(sound1, nbwindows=(duration/5)) > 1566.69 acoustic_complexity(sound1) # j is set to 5 by default > 1567.414
Changing the cluster size j to 10 sec:
ACI(sound1, nbwindows=(duration/10)) >783.8312 acoustic_complexity(sound1, j=10) > 784.0986
The difference between the results from each package seems to come from how each function uses the clumping argument, j, which is set to 5 seconds as a default in both the SoundscapeMeter software and soundecology.
Sueur J., Aubin T., Simonis C. (2008). Seewave: a free modular tool for sound analysis and synthesis. Bioacoustics, 18: 213-226.
Vignette “Differences of ACI values between seewave and soundecology” by LJ Villanueva-Rivera
Version 1.0 (21 December 2015)