The carefully tailored acoustic pulses emitted by the VIPER provide an abrupt wavefront that reduces ambiguity in spatial perception even if simply providing a higher signal-to-noise ratio of the returning wavefront. However, those pulses are also interesting in that there is a phenomenon known as the precedence effect, which describes a psychoacoustic masking of subsequent wavefronts after a first wavefront is perceived. The duration over which the masking persists is dependent upon the nature of the sound being heard, with a shorter duration of masking for acoustic pulses and longer duration for more complex sounds. Accordingly, the carefully tailored acoustic pulses of the VIPER provide advantage not only in perceiving the range of the closest acoustically reflective object, but also in resolving additional objects at greater distances.

Recent research suggests that a person's engagement in an echolocation task, as opposed to mere listening, can reduce psychoacoustic echo suppression. As the experiment distinguished between listening to exogenous sounds and engaging in echolocation using self-vocalized sounds, it appears some question may remain as to how echo suppression may be affected when engaging in echolocation using exogenous sounds. While control experiments were performed to attempt to distinguish effects of self-vocalized sounds vs. exogenous sounds, it is questionable whether the duration of such experiments were commensurate with the on-going duration of interaction of a user with the VIPER.

One question I have is whether a user's extended interaction with the VIPER can inhibit echo-suppression during the echolocation task even with exogenous sounds. One phenomenon that could conceivably support such improved performance over time is neuroplasticity.

Even if the precedence effect were not appreciably reduced, that is not problematic for the VIPER, as precedence effect still allows perception of the echo from the closest acoustically reflective object, which being nearest to the person using the VIPER, is likely a more important object of which to be aware than objects farther from the person.

http://www.psychologicalscience.org/index.php/publications/observer/2015/december-15/using-sound-to-get-around.html

http://rspb.royalsocietypublishing.org/content/280/1769/20131428