Acoustic Barcodes are structured patterns of physical notches that, when swiped with a fingernail, produce a complex sound that can be resolved to a unique ID number. A single, inexpensive contact microphone attached to a surface or object is used to capture the waveform. Acoustic Barcodes could be used for information retrieval or to triggering interactive functions. They are passive, durable and inexpensive to produce. Further, they can be applied to a wide range of materials and objects, including plastic, wood, glass and stone.