The Sonar of Dolphins

1 Introduction.- 1.1 Historical Perspective.- 1.2 Some Underwater Acoustics.- 1.3 The Time and Frequency Domains.- 1.4 Experimental Psychological Methodology.- 1.5 Signal Detection Theory.- 2 The Receiving System.- 2.1 The Outer Ears.- 2.2 The Middle Ear.- 2.3 The Inner Ear.- 2.4 Summary.- 3 Characteristics of the Receiving System for Simple Signals.- 3.1 Hearing Sensitivity.- 3.2 Spectral Analysis Sensitivity.- 3.3 Directional Hearing.- 3.4 Response Bias and Sensitivity in Hearing.- 3.5 Summary.- Appendix: Derivation of the Receiving Directivity Index.- 4 Characteristics of the Receiving System for Complex Signals.- 4.1 Perception of Click Signals.- 4.2 Perception of Time Separation Pitch.- 4.3 Summary.- 5 The Sonar Signal Transmission System.- 5.1 Preliminary Examination of Biosonar Signals.- 5.2 Sound Production Mechanism.- 5.3 Acoustic Propagation in the Dolphin’s Head.- 5.4 Summary.- 6 Characteristics of the Transmission System.- 6.1 The Concept of Near and Far Acoustic Fields.- 6.2 The Dolphin Near- to Far-Field Transition Region.- 6.3 The Acoustic Field on a Dolphin’s Head.- 6.4 Directional Pattern of Biosonar Signals.- 6.5 Equivalent Planar Circular Aperture.- 6.6 Summary.- 7 Characteristics of Dolphin Sonar Signals.- 7.1 Click Intervals.- 7.2 Frequency Characteristics.- 7.3 Click Source Levels.- 7.4 Number of Clicks and Response Latencies.- 7.5 Signals from Other Species.- 7.6 Summary.- 8 Target Detection Capability of the Active Sonar System.- 8.1 The Physics of Acoustic Reflection by Targets.- 8.2 Noise-Limited Form of the Sonar Equation.- 8.3 Biosonar Detection Capabilities.- 8.4 Detection of Complex Echoes.- 8.5 Comparison Between a Dolphin and an Ideal Receiver.- 8.6 Target Detection in Reverberation.- 8.7 Summary.- 9 Biosonar Discrimination, Recognition, and Classification.- 9.1 Mathematical Tools for the Analysis of Target Echoes.- 9.2 Target Size Discrimination.- 9.3 Target Structure Discrimination.- 9.4 Target Shape Discrimination.- 9.5 Delayed Matching to Sample.- 9.6 Target Range Difference Discrimination.- 9.7 Insights from Human Listening Experiments.- 9.8 Summary.- 10 Signal Processing and Signal Processing Models.- 10.1 Analysis of Dolphin Sonar Signals.- 10.2 The Dolphin Modeled as an Energy Detector.- 10.3 Signal Processing Models for Target Recognition.- 10.4 Artificial Neural Networks and Target Recognition.- 10.5 Summary.- 11 Comparison Between the Sonar of Bats and Dolphins.- 11.1 Comparison of Sonar Signals.- 11.2 Comparison of Signal Detection Capabilities.- 11.3 Comparison of Target Discrimination Capabilities.- 11.4 Doppler Compensation and Flutter Detection.- 11.5 Summary.- 12 Road Map for Future Research.- 12.1 Mechanisms of Sound Reception and Hearing.- 12.2 Mechanisms of Sound Production and Transmission.- 12.3 Biosonar Capabilities and Mechanisms.- 12.4 Signal Processing Models.- 12.5 Natural and Dynamic Biosonar Behavior.- 12.6 Concluding Remarks.