Analyzing Long-Term Changes in Soundscapes Using Power Spectral Band Sums

Various species of fish make sounds (individually and in choruses) while mating and for aggressive encounters. Recording the sounds of fishes in mixed-species choruses has been done for 26 years in Pamlico Sound, North Carolina, USA. But the changing contributions of the various fishes to the soundscape that varies diurnally, seasonally, and over 20 years have not been characterized. Multiple passive acoustic recording systems have been used to make these recordings at a variety of locations. After calibrating these recording systems, an analysis of the soundscape was performed using power spectral band (PSB) sums, which sum the acoustic energy in frequency bands associated with known soniferous fish species. The analysis reveals some interesting patterns related to fish ecology: (1) sound production occurs after sunset with a nightly peak in sound pressure levels; (2) there is a seasonal increase in the power spectral band sums, correlated with increasing water temperatures; and (3) species in the Sciaenidae family have distinct periods of sonic activity. The temporal progression of these species in their spawning areas was plotted using PSB sums. Examples are presented of these soundscapes and descriptions of the changes observed in the soundscapes from samples taken over 20 years (1997–2018).