Abstract
An experiment was conducted to investigate how variability in the acoustic channel impulse response at signal processing timescales of seconds to minutes is related to internal-wave-driven changes in the ocean sound speed field on timescales of tens of minutes. We find that vertical fine-scale structures (≤10 m) embedded in the sound speed profile have strong second derivatives which allow for the formation of acoustic caustics as well as acoustic propagation pathways that interfere with each other (micro-multipaths). Both effects are sensitive to vertical displacement by internal waves, which can therefore produce sub-minute acoustic fluctuations from internal waves that have timescales longer than a minute.
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