A comprehensive computational model of animal biosonar signal processing
Fig 6
Enhanced registration of nulls by amplitude-latency trading.
Dechirped SCAT spectrograms for FM pulse and two-glint echoes with (A) 30 μs glint delay separation and (B) 100μs glint delay separation. Threshold crossings (threshold #3) are marked by circles (orange for no amplitude-latency trading (i.e., just threshold crossing delay); blue for amplitude-latency trading (i.e., threshold crossing delay augmented to 25 μs longer latency per dB attenuation). Inset in B shows magnified view of one null in the 100-μs echo. The 6ms range delay is marked by the leading (left) vertical edge of the row of dots for each echo. Without amplitude-latency trading, the nulls appear as interruptions, or voids, in the orange spectrograms, with a slight rightward trend as frequency approaches the center of the null and the lower amplitude moves the threshold crossings to slightly longer times. The deviations from the range delay can be used to estimate each null’s frequency entirely using threshold-crossing timing information.