Can soundscape indices be used to reflect biodiversity?
Check out this report by Ailsa Lamond, former student of the University of Sussex:
http://sro.sussex.ac.uk/id/eprint/65370/
She analysed recordings of Santa Lucía's bird monitoring program and came to quite a few interesting results, some of which (as she mentions herself) seem somewhat counterintuitive. It's a highly entertaining read.