> Does sound have usable distinguishing features other than just loudness? Than raw, peak amplitude? yes. Frequency and amplitude variation over time will be

> Does sound have usable distinguishing features other than just loudness? Than raw, peak amplitude? yes. Frequency and amplitude variation over time will be roughly consistent in a linear system (i.e. the sound will get louder and quieter over time). If you have a stable, well-qualified listening system (such as, for example, a set of fixed recording locations in an environment that is acoustically static), you can build a map of how sound sources map to each recorder, and use principles of directed arrays to get very accurate location projections. To use your example, yes it would be difficult for you and a single friend to confirm that you heard the same sound, but you could come up with a probability that if you heard a sound with the same characteristics with a certain time difference and loudness difference, it is likely to have been from a certain location. If, however, you have 4 friends, it gets much less likely that all 4 heard a different sounds calibrated exactly to seem like they came from a specific source when the data is combined.