Characterization of acoustic attenuation in a coral reef environment

Abstract

Coral reefs are complicated and understudied acoustic propagation environments. In addition to geometric spreading, there are propagation losses due to bottom attenuation, volumetric scattering, and boundary scattering from bathymetric variability and sea surface roughness. On a Hawaiian coral reef, a field test was performed in shallow water during which low-level tones were projected from an underwater speaker and received by a single hydrophone at various ranges up to 500 m from the source. Acoustic data gathered during the field test were analyzed to characterize the sound propagation environment. Conventional geometric spreading assumptions were challenged for the sloping bathymetry characteristic of the Hawaiian coral reef environment. Geoacoustic parameters of the coral reef environment were extracted from transmission loss measurements using a nonlinear least-squares inversion. Losses were estimated for frequencies of 500 Hz, 2 kHz, 5 kHz, 10 kHz, and 15 kHz.Coral reefs are complicated and understudied acoustic propagation environments. In addition to geometric spreading, there are propagation losses due to bottom attenuation, volumetric scattering, and boundary scattering from bathymetric variability and sea surface roughness. On a Hawaiian coral reef, a field test was performed in shallow water during which low-level tones were projected from an underwater speaker and received by a single hydrophone at various ranges up to 500 m from the source. Acoustic data gathered during the field test were analyzed to characterize the sound propagation environment. Conventional geometric spreading assumptions were challenged for the sloping bathymetry characteristic of the Hawaiian coral reef environment. Geoacoustic parameters of the coral reef environment were extracted from transmission loss measurements using a nonlinear least-squares inversion. Losses were estimated for frequencies of 500 Hz, 2 kHz, 5 kHz, 10 kHz, and 15 kHz.