We characterize the sources of background noise recorded by an ocean‐bottom seismometer array deployed on the oldest oceanic lithosphere of the western Pacific plate. This igneous oceanic crust is blanketed up to 1000 m cover of sediments, making it a unique place to investigate correlations between sediment thickness and background noise levels in the marine environment. Although the data are limited, we found that the thicker sediments attenuated short‐period noise levels and amplified long‐period noise levels, in agreement with observations made for seismic arrivals in onshore sedimentary basins. Comparison of the noise levels from our Oldest‐1 deployment with those (1) in the western Pacific basin, (2) near the Mariana trench, and (3) offshore New Zealand indicates that the Oldest‐1 has the highest noise levels in the double‐frequency (secondary) microseism band by up to 7 dB. This result was unexpected given the greater water depths (averaging 5800 m) for the Oldest‐1 array. However, even at these great depths, we find a strong correlation between significant wave heights and background noise levels in the short‐period microseism band (2–5 s). In addition, the Oldest‐1 array was subjected to a great number of intense close typhoons than the other arrays and was proximal to a great number of taller seamounts than the other arrays. Finally, tracking noise source azimuths using station pairs led to the identification of a possible new source for the single‐frequency microseism band in the coastal areas of Papua New Guinea and Australia.

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