Abstract: Disclosed herein are various embodiments of devices, methods and systems for securing or coupling a string of downhole geophysical sensors to the sidewall of a borehole, using an expandable member configured to be deployed into an expanded position when at least one geophysical sensor is located at a desired depth in a borehole, the expandable member being configured to engage at least portions of the sidewalls and prevent the passage of a securing or coupling material around or through the geophysical sensor when the securing or coupling material is poured around the geophysical sensor when the expandable member is in the open or expanded position. This allows the securing and acoustic coupling of downhole geophysical sensors to the sidewall of a borehole while avoiding problems caused by transmission of surface noise into the subsurface resulting from pouring securing or coupling material to fill the entire well bore.