Biomedical subjects

R Aubauer

Publications and source records attributed to R Aubauer.

3 recordsLinked to original sources

PubMed2000

One-hydrophone method of estimating distance and depth of phonating dolphins in shallow water.

Previous attempts at localizing cetaceans have generally used multiple hydrophone arrays and multichannel recording systems. In this paper, a low-budget localization technique using only one hydrophone is described. The time delays of the signals traveling via the surface and bottom reflection paths to the hydrophone, relative to the direct signal, are used to calculate the distance and the depth of a phonating animal. Only two additional measures, the depth of the bottom and hydrophone, have to be taken. The method requires relatively shallow waters and a flat bottom surface. Echolocating and burst pulsing Hawaiian spinner dolphins (Stenella longirostris) at the Waianae coast of Oahu, Hawaii, were localized over different bottom substrates. A tracking range of up to 100 m was achieved. The accuracy of the method is estimated by the total error differential technique. The relative distance estimation error is below 35% and the absolute depth error below 0.7 m, so that the location method is sufficiently precise for examining source levels in our study area. Because of its simplicity, the method ideally complements sound recordings and visual sightings of marine mammals and could lead to a better understanding of the nature and use of click trains by dolphins.

Animal Communication↗

PubMed2000

Classification of electronically generated phantom targets by an Atlantic bottlenose dolphin (Tursiops truncatus).

Animal behavior experiments require not only stimulus control of the animal's behavior, but also precise control of the stimulus itself. In discrimination experiments with real target presentation, the complex interdependence between the physical dimensions and the backscattering process of an object make it difficult to extract and control relevant echo parameters separately. In other phantom-echo experiments, the echoes were relatively simple and could only simulate certain properties of targets. The echo-simulation method utilized in this paper can be used to transform any animal echolocation sound into phantom echoes of high fidelity and complexity. The developed phantom-echo system is implemented on a digital signal-processing board and gives an experimenter fully programmable control over the echo-generating process and the echo structure itself. In this experiment, the capability of a dolphin to discriminate between acoustically simulated phantom replicas of targets and their real equivalents was tested. Phantom replicas were presented in a probe technique during a materials discrimination experiment. The animal accepted the phantom echoes and classified them in the same manner as it classified real targets.

Acoustics↗

PubMed1998

Phantom echo generation: a new technique for investigating dolphin echolocation.

In behavioral experiments where real targets are used to investigate dolphin echolocation, it is often very difficult to extract the relevant echo parameters that the animals use to discriminate or classify. The complex relationship between the physical dimensions and the reflection characteristic of real targets prevents separate control of various echo parameters of the stimuli presented in an echolocation experiment. A new echo simulation method presented in this paper avoids this problem. Dolphin echolocation sounds are transformed with the target impulse response into artificial echoes, which are played back to the animal. The phantom echo system is implemented on a digital signal processing board and gives an experimenter fully programmable control over the echo generating process and the echo structure itself. Echoes of several underwater targets were simulated to evaluate the quality of the method. A comparison of simulated echoes with the original echoes demonstrated very good agreement independent of the incident signal (cross-correlation coefficient > 0.95). The method has tremendous potential for investigating animal echolocation and understanding biosonar signal processing.

Acoustic Stimulation↗