Nonacoustic noise interference in measurements of infrasonic ambient noise

Three potential nonacoustic noise sources which can interfere with low-frequency measurements of underwater ambient noise are examined. All of them are flow induced and require relative motion between the hydrophone and the water around it. Two of them result from the response of the hydrophone to different types of nonacoustic pressure fluctuations developed on the hydrophone surface by the flow. The third noise source results from the incidental sensitivity of the hydrophone to temperature inhomogeneities normally existing in the sea. It is shown that both types of flow-induced pressure fluctuations can be significant under conditions encountered in the open sea, whereas interference due to temperature fluctuations will be negligible except under unusual circumstances.