The electronics digitizes the noise downhole and sends a frequency spectrum to the surface to be recorded. Both the frequency spectrum and six high-pass frequency cuts are displayed on a log, providing a quantitative measurement of the downhole noise. The NTO can be combined with other Sondex Wireline tool sand logs data in both memory or surface read out tool strings. Consequently, any cased hole logging intervention, such as production logging, cement evaluation or pipe inspection, becomes an opportunity to verify the integrity of downhole components at minimal additional cost.