title: Multi-component separation and analysis of bat echolocation calls.
abstract: The vast majority of animal vocalizations contain multiple frequency modulated (FM) components with varying amounts of non-linear modulation and harmonic instability. This is especially true of biosonar sounds where precise time-frequency templates are essential for neural information processing of echoes. Understanding the dynamic waveform design by bats and other echolocating animals may help to improve the efficacy of man-made sonar through biomimetic design. Bats are known to adapt their call structure based on the echolocation task, proximity to nearby objects, and density of acoustic clutter. To interpret the significance of these changes, a method was developed for component separation and analysis of biosonar waveforms. Techniques for imaging in the time-frequency plane are typically limited due to the uncertainty principle and interference cross terms. This problem is addressed by extending the use of the fractional Fourier transform to isolate each non-linear component for separate analysis. Once separated, empirical mode decomposition can be used to further examine each component. The Hilbert transform may then successfully extract detailed time-frequency information from each isolated component. This multi-component analysis method is applied to the sonar signals of four species of bats recorded in-flight by radiotelemetry along with a comparison of other common time-frequency representations.
authors.affiliation: Naval Undersea Warfare Center, 1176 Howell Street, Newport, Rhode Island 02841, USA.
authors.forename: John
authors.initials: J
authors.lastname: DiCecco
authors.forename: Jason E
authors.initials: JE
authors.lastname: Gaudette
authors.forename: James A
authors.initials: JA
authors.lastname: Simmons
mesh_terms: D000465:Algorithms; D000818:Animals; D002685:Chiroptera / Q000502:physiology*; D004455:Echolocation; D005426:Flight, Animal; D005583:Fourier Analysis; D017711:Nonlinear Dynamics; D013018:Sound Spectrography; D013045:Species Specificity; D013686:Telemetry; D013997:Time Factors