Sanitary sewer overflows (SSOs) are most often caused by the long-term buildup of roots, fats, oils or grease within a pipe. An acoustic inspection is a cost-effective way to detect blockages before an overflow or maintenance issue occurs. A transmitter is installed in a manhole that transmits a series of tones through the air gap within the pipe. A receiver is installed in an adjacent manhole and it listens for degradation in tones compared to a clean pipe. The data are analyzed in less than three minutes and rate the severity of the blockage on a scale from 0 to 10.