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# hygromycin b If we take into account the effect of

If we take into account the effect of diffraction, it becomes clear that the efficiency of MF shielding at the measured frequencies would have been the same at a constant ratio of the screen size to the wavelength. This is also attested by the fact that the threshold values change inversely proportional to the wavelength (see Fig. 4). Unfortunately, at low frequencies, it is difficult to provide the same ratio between the shield dimensions and the stimuli wavelength as for the frequency of 100kHz, as the shield dimensions would be too large in this case (for example, 1.9m for a frequency of 8kHz), and because of this, the efficiency of the hood used decreases with the decreasing frequency.
The original results obtained in this study indicate that the MF are involved in receiving and conducting sounds to the mandibular fat and further to the tympanic wall, i.e., to the middle ear, providing a unique sound-conducting channel. This fact excludes the possibility of sound conduction through other hygromycin b [4,7,8,19–23].
MF shielding efficiency at frequencies below 6kHz was not measured in the present study, but we can assume that sound is received and conducted by the same unique channel, i.e., through the MF, at low frequencies as well. This is supported by the constant slope (9–10dB/octave) of the low-frequency branch of the dolphin\'s audiogram [15], which starts at about 0.1kHz and extends up to 20–30kHz.

Conclusion
The results of measuring these auditory thresholds with the mental foramina area shielded and unshielded provide further experimental confirmation for the hypothesis advanced concerning the decisive role of the morphological structures of the dolphin\'s mandible as a new peripheral region of its auditory system [11–13,24–26]. This hypothesis was based on the results of a morphological study and of modeling the system under consideration.
Thus, mental foramina act as the new outer ear canals. They are involved in receiving and conducting sounds to the mandibular fat in the whole frequency range of the dolphin\'s hearing (0.1–160kHz). The mandibular fat transmits the sounds to the lateral wall of the tympanic bone, i.e., to the middle ear and the cochlea, which is consistent with Refs. [3–6]. The results of this study give reason to assume that the toothed whales (Odontoceti) possess this new peripheral hearing region due to the similarity of their morphology.

Introduction
The first study on calculating cantilever plates was carried out by Holl [1], who used the finite difference method (FDM, also called the grid method) for a wide plate with an aspect ratio of 4:1. A concentrated force applied in the center of the free edge opposite to the clamped one served as the load. This method was also used by many authors for different types of loads, plate aspect ratios and grid spacings. The finite element method (FEM) was first applied by Zienkiewicz and Cheung [2]; they divided a square plate into nine square elements and considered the case of a uniform load. Other approximate techniques, such as the Rayleigh–Ritz, the Bubnov–Galerkin and the Kantorovich–Vlasov methods, and others, were also used to solve this problem. Study [3] applied the method of infinite superposition of correcting functions in terms of hyperbolic trigonometric series in order to find the deflection function; in the course of the application of the method, all residual errors in the boundary conditions tended to zero, providing an exact solution of the problem in the limit.

Homogenous solutions and relations of generalized orthogonality of elastic rectangular plates
A solution of the biharmonic equation
was sought for by Papkovich [4] in the form
where ∇2 is the two-dimensional Laplace operator, w is the plate deflection, are the series coefficients, are the eigenvalues, and (y) are the eigenfunctions of the problem. For a plane elasticity problem, w is the Airy function, and in the case of thin plate bending it is the deflection. After sum (2) is substituted into Eq. (1), an ordinary differential equation is obtained for the (y) functions: