Accurate estimates of acoustic absorption in seawater are crucial to the acoustic estimation of aquatic biomass. Estimates of acoustic absorption were obtained via a “pulse-echo” method, implemented using commonly available scientific echosounders and spherical calibration targets over a range of discrete frequencies. Below about 200 kHz, the absorption estimates were not significantly different from those of existing formulas, but at around 333 kHz, the measured absorption was 15 dB km⁻¹ higher than estimated from existing formulas. Measurement variability was about ±2 dB km⁻¹ for all frequencies. This is consistent with an observed anomaly between modelled and measured frequency-dependent biological backscatter. Allowing for this deviation will avoid incorrect spectral-based classification of acoustic targets and improve uncertainty in aquatic biomass estimation.

中文翻译：

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在38至360 kHz的海水中进行声吸收的现场测量。

海水中吸声的准确估算对于水生生物量的声学估算至关重要。声学吸收的估计值是通过“脉冲回波”方法获得的，该方法使用常见的科学回声测深仪和球形校准目标在一系列离散频率上实施。在大约200 kHz以下，吸收估计值与现有公式的估计值并无显着差异，但是在大约333 kHz处，测得的吸收值比现有公式估计的值高15 dB km ^-1。测量变化约为±2 dB km ^-1对于所有频率。这与在建模和测量的频率相关的生物反向散射之间观察到的异常一致。允许这种偏差将避免基于频谱的声学目标分类错误，并改善水生生物量估算的不确定性。