PMC

Directionality of the eardrum in Hemidactylus before (A) and after (B) occluding the contralateral eardrum with a dome of Vaseline. In C, the left naris was additionally blocked with Vaseline, and the plot shows the amplitude ratio (in decibel) of nares block to the eardrum-blocked condition.

Interaural transmission gains in Hemidactylus (left), Anolis (middle), and Basiliscus (right, smoothed data) calculated as the ratio of contra- and ipsilateral transfer functions. Data from individual animals, see “” for details. A Amplitudes, B phases in the three lizard species.

Interaural transmission gain in Hemidactylus. The interaural transmission gain is calculated as the ratio of contra- and ipsilateral transfer functions, as described in “”. Only the amplitude spectrum is shown here. The two curves are the gain functions with (red curve) and without (black curve) correction for direct transmission of sound (see “” for details).

Individual variation in the three species. Each figure shows the eardrum vibration transfer functions in response to free-field stimulation from IL (90°) and CL (−90°, dotted lines) directions in Anolis (left, two individuals), Hemidactylus (middle, three individuals), and Basiliscus (right, two individuals). Each animal is identified by color. The CL stimulation responses are in all cases lower than IL responses.

A Eardrum vibration amplitude as a function of sound direction in three lizard species: the gecko Hemidactylus (left), anole Anolis (middle), and basilisk Basiliscus (right). X axis Direction angle in degrees (ipsilateral directions are positive, contralateral negative, 0° is frontal); Y axis frequency (hertz). The color scale is the eardrum vibration amplitude transfer function (decibel re. 1 mm/s/Pa). B The lower row shows interaural vibration difference (see ‘’ for details) in Anolis (left), Hemidactylus (middle), and Basiliscus (right). X axis direction; Y axis frequency; color scale is interaural difference (decibel).

Reconstruction and modeling of the free-field response of the eardrum of Hemidactylus (left) and Anolis (right). The spectra are eardrum transfer functions to sound from the seven frontal directions. For comparison, measured free-field response spectra from two individual animals are shown in the top row (A). The middle row (B) shows reconstructions, calculated as described in “”, from measurements in the same individuals as in A. The bottom row (C) shows model calculations of eardrum vibration. The eardrum impedance was calculated from the gain measurements and used in a lumped-element model of the lizard ear (see “” for details). Model data are only shown for one Hemidactylus (left) and an Anolis specimen. For Basiliscus, the transmission gain phase data (Fig. ) are too noisy to be usable. For each animal, calculations from four directions are shown.