Sound Fields in Two Small Experimental Test Arenas: A Comparison

Lab-based bioacoustics experiments on fish enable control of confounding factors, yet these experiments often use small tanks that are spatially complex in terms of particle motion and sound pressure levels (SPL). One solution is to submerge an arena in water so the influence of the walls on the acoustic environment is greatly reduced. The experiment answered the following: (1) Can the sound pressure homogeneity in small tanks be improved? (2) Can the particle acceleration (PA) levels in small tanks be reduced? (3) Does submerging small tanks allow the sound field to be reliably described by progressive plane waves? The first setup consisted of a rectangular tank surrounded by air (in-air tank) and the second setup was a cylindrical arena submerged in water (submerged arena). Measurements of a 1 s, 125 dB tone at 400–2000 Hz were taken and mapped. The submerged arena possessed less heterogeneity in SPL and lower levels of PA than the in-air tank. The predicted PA (calculated to fulfill research question three) was a better approximation to the submerged arena than the in-air tank. This study demonstrates that the submerged arena gave greater control over the stimulus that a fish experiences in lab-based experiments.