BIOACOUSTICSTable of Contents: Volume 12
BIOACOUSTICS
Special issue on Fish Bioacoustics
Edited by Arthur N. Popper, Jacqueline F. Webb and Richard R. Fay
SECTION I - Introduction and Historical Perspectives
SECTION II - Structure and Function of the Fish Auditory System
SECTION III - Bioacoustics and the Lateral Line System
SECTION IV - Hearing
SECTION V - Sound Source Localisation
SECTION VI - Sound Production
SECTION VII - Bioacoustic Behaviour
SECTION VIII - Bioacoustic Oceanography
SECTION IX - Applied Bioacoustics
SECTION X - New Methods in Fish Bioacoustics
Holland, J., Dabelsteen, T., Pedersen, S.B. & López Paris, A. (2001). Potential ranging cues contained within the energetic pauses of transmitted wren song. Bioacoustics 12(1): 3-20
Abstract
Many species of songbirds appear to use received song to estimate the relative distance to singing conspecifics (ranging). Habitat-induced degradation offers relevant cues. Reverberations extend transmitted elements with a 'tail' of energy, which effectively fills inter-element pauses and can overlie successive elements. We use a transmission experiment to investigate this tail energy in wren Troglodytes troglodytes song. Our quantification uses a technique which results in a tail-to-signal ratio (TSR) and a measure of the rate of tail energy decline (RTD). Both measures vary with transmission distance; TSR increases whilst RTD decreases. We conclude that these kind of features of the tail energy could potentially operate as ranging cues. In addition, we quantify the decay of the undegraded elements. The element decay is markedly faster than the decline of the tail energy once the elements have been transmitted. We suggest that this could provide wrens with the opportunity to differentiate between non-transmitted sound (their own) and transmitted song. A strategy whereby energies are compared absolutely could be operative independently of familiarity with the specific song type received.
Keywords: ranging, degradation, reverberations, wren, Troglodytes troglodytes.
Hammer, O. & Barrett, N. (2001). Techniques for studying the spatio-temporal distribution of animal vocalizations in tropical wet forest. Bioacoustics 12(1): 21-35
Abstract
An array of four microphones was set up in two rain forest locations in Costa Rica, and 12-14 hours of sound were recorded over a 24-hour period at each location. Using this acoustical location system, the distribution of animal signaling in time, space and frequency could be assessed. This study demonstrates the feasibility of localizing some animals acoustically even under difficult field conditions in a highly reverberant and noisy environment. Primates seem to be particularly easy to track using this method, while birds seem more problematical. We also advocate the use of long-term indiscriminate acoustical sampling of all vocalizers, in order to give information about the synecology of animal communication. Long-term spectral analysis and data reduction by Principal Components Analysis provide tools for comparing acoustical samples over time and space.
Keywords: Microphone array, acoustical localization, Costa Rica, Alouatta, Ateles, Dendrobates, principal components analysis.
Clayton, D. (2001). Acoustic calling in four species of ghost crabs (Ocypode jousseaumei, O. platytarsus, O. rotundata and O. saratan) (Brachyura: Ocypodidae). Bioacoustics 12(1): 37-55
Abstract
Acoustic calling and the mechanisms of its production are described or the ghost crabs Ocypode jousseaumei, O . platytarsus, O. rotundata, and O. saratan from Oman. Sounds generated by the major cheliped suggest the existence of species specific differences, predominantly in the temporal properties of rapping and in the physical structure of stridulation. The spectral energy of all sounds is concentrated at frequencies below 4 kHz. O. rotundata and O. saratan build sand pyramids adjacent to their courtship burrows and are considerably less acoustically active than O. jousseaumei and O. platytarsus that do not build pyramids, suggesting that the visual signal is substituted by an auditory one.
Keywords: acoustic calling, Ocypode, rapping, stridulation.
Houser, D.S., Helweg, D.A., Moore, P.W.B. & Chellapilla, K. (2001). Optimizing models of dolphin auditory sensitivity using evolutionary computation. Bioacoustics 12(1): 57-78
Abstract
Object classifiers that attempt to mimic dolphin echolocation require an auditory weighting function representative of dolphin peripheral auditory processing. An evolutionary program (EvPg) was used to fit the frequency-dependent output of a bank of bandpass filters to the auditory sensitivity of the bottlenose dolphin, Tursiops truncatus. Pseudo-Gaussian (PG) and rounded exponential (ROEX) functions were used to describe individual filter shapes. Variables determining the number of filters per model overall filter shape and amplitude scaling were submitted to the EvPg for optimization. Maximum deviation (Pe) between model output and the sensitivity of the dolphin was used as a measure of similarity between the two, i.e., lower Pe indicated a greater similarity. The number of filters converged upon 37 for all ROEX models and ≤ 45 of all PG models. The Pe of the best-performing PG model was 0.08, and for all ROEX models was 0.13. Greatest deviations typically occurred below 5 kHz and above 130 kHz. Relative audiometric sensitivity of a dolphin ear model has been improved relative to previous models, thereby providing an auditory weighting function more representative of dolphin peripheral auditory processing. This model will be applied to further investigate how dolphins use echolocation to discriminate among objects.
Keywords: auditory model, spectrum filter, dolphin, evolutionary programming, ear filter