Abstract:

It is hypothesized that proportional changes in echo amplitude and carrier frequency might aid obstacle avoidance in cf bats by means of acoustic flow perception. This approach appears to be feasible in principle for single targets, however, obstacle avoidance, unlike prey capture in midair, is invariably prone to constitute a multiple target problem, which has to be addressed in assessing the hypothesis' validity. In order to map a compound excitation pattern formed by superposition of responses to multiple echoes back into target space by means of an acoustic flow approach, instantaneous (carrier) frequency and amplitude together with their first-order derivatives must be recovered individually for each echo to be perceived as a separate entity. The primal sketch serving as a substrate for this operation is impoverished in that it is only preserving response envelopes. At the same time, the system design might capitalize on knowledge about the transfer functions of the filter bank's channels as well as at least a rough guess about the echo spectrum. Consequently, it is attempted to explain compound excitation patterns as a sum of superimposed responses to individual echoes, which are known for any given frequency location to a scaling constant.