Systems and methods for distance independent differential signature detection

A differential signature detection system, the system comprising:

• at least one target sensor, wherein the at least one target sensor is configured to measure acoustical signals within a first narrow band around a target frequency;
• at least one offset sensor, wherein the at least one offset sensor is configured to measure acoustical signals within a second narrow band around an offset frequency;
• and
• a controller coupled to the at least one target sensor and the at least one offset sensor, wherein the controller is configured to:
• compare a signal output of the at least one target sensor with an output of the signal output of the at least one offset sensor to calculate a differential measurement that comprises a difference in signal peak intensity;
• compare the differential measurement to a reference signal, wherein the reference signal comprises a threshold indicative of a presence of a characteristic signature peak associated with a target object;
• and
• produce an output based on the comparison between the differential measurement and the reference signal.