1. An apparatus for detecting an anomaly in a monitored volume, comprising: a plurality of transducers coupled to a respective plurality of localized portions of said monitored volume, each of said transducers outputting a respective analog electrical signal having a low-frequency component which is a function of the vibrational displacement of said localized portions of said monitored volume; means for converting said respective analog electrical signals into respective digital electrical signals; means for multiplexing said respective digital electrical signals from said respective transducers; and neural network processing means for recognizing a predetermined pattern in the digital electrical signals of any transducer having said predetermined pattern masked by background noise, said predetermined pattern reflecting a possible anomaly in said monitored volume.