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Evidence for double acoustic windows in the dolphin, Tursiops truncatus
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Image of FIG. 1.
FIG. 1.

(a) Experimental paradigm for finding a sound-receiving point by acoustic delays. O—reference point, X—searched-for sound receiving point, and —opposite positionS of the sound source S, and —distances from positions and to the point X, —radius of the circle of sound-source movement, —distance from the reference point O to the point X, —azimuth of the point X. (b) Dependence of source-to-receiver distance on sound-source azimuth; the middle distance is taken as arbitrary zero; and —cosine function amplitude and phase.

Image of FIG. 2.
FIG. 2.

Experimental design. (a) Dorsal view. (b) Lateral view. Explanation in text.

Image of FIG. 3.
FIG. 3.

(a) Stimulus waveform. (b) Stimulus spectrum, 1—electric signal, 2—sound signal played through a transducer frequency response of /oct.

Image of FIG. 4.
FIG. 4.

(a) Examples of ABRs at different sound-source positions and sound intensities. Stimulus frequency . 1—azimuth 0°, intensity ; 2—0° , 3—165° . (b) Cross-correlation functions of waveforms 1 and 2 and waveforms 1 and 3 (functions 1:2 and 1:3, respectively).

Image of FIG. 5.
FIG. 5.

(a) Dependence of ABR magnitude (M, left scale) and delay relative to the shortest latency (D, right scale) on stimulus intensity. (b) Dependence of ABR delay on magnitude. Stimulus frequency .

Image of FIG. 6.
FIG. 6.

(a) ABR delay (relative to the shortest latency) dependence on sound-source azimuth. Probe frequency . Thin lines—four sets of measurements, solid line—average of the four. (b) ABR magnitude dependence on sound-source azimuth [thin and solid lines—the same as in (a)]. (c) 1—delay dependence on azimuth corrected for delay-vs-magnitude dependence; 2—average (with standard errors) of the left and right branches of (1); 3—approximating cosine function.

Image of FIG. 7.
FIG. 7.

(a) Determination of a sound receiving point for frequency. (a) Experimental data and approximating cosine function for four reference points, from behind the melon tip, as indicated. (b) Vectors drawn from the four reference points according to the cosine function parameters; black solid point—mean of the four found positions; ellipse—SD area.

Image of FIG. 8.
FIG. 8.

The same as Fig. 7, for frequency.

Image of FIG. 9.
FIG. 9.

Positions of sound-receiving points for frequencies from . Each position (solid dot) is an average of four positions found with four different reference points. Ellipses delimit SD areas for each sound-receiving point. Point positions are superimposed on a contour of the dorsal view of the dolphin’s head. Rt—rostrum tip, Mt—melon tip, Bh—blowhole, Am—auditory meatus.


Generic image for table

Parameters of cosine functions approximating experimental data.

Generic image for table

Estimates of receiving point positions.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Evidence for double acoustic windows in the dolphin, Tursiops truncatus