Milan Cervenka

Male moth songs tempt females to accept mating: the role of acoustic and pheromonal communication in the reproductive behaviour of Aphomia sociella.

Background Members of the subfamily Galleriinae have adapted to different selective environmental pressures by devising a unique mating process. Galleriinae males initiate mating by attracting females with either chemical or acoustic signals (or a combination of both modalities). Six compounds considered candidates for the sex pheromone have recently been identified in the wing gland extracts of Aphomia sociella males. Prior to the present study, acoustic communication had not been investigated. Signals mediating female attraction were likewise unknown. Methodology/Principal Findings Observations of A. sociella mating behaviour and recordings of male acoustic signals confirmed that males initiate the mating process. During calling behaviour (stationary wing fanning and pheromone release), males disperse pheromone from their wing glands. When a female approaches, males cease calling and begin to produce ultrasonic songs as part of the courtship behaviour. Replaying of recorded courting songs to virgin females and a comparison of the mating efficiency of intact males with males lacking tegullae proved that male ultrasonic signals stimulate females to accept mating. Greenhouse experiments with isolated pheromone glands confirmed that the male sex pheromone mediates long-range female attraction. Conclusion/Significance Female attraction in A. sociella is chemically mediated, but ultrasonic communication is also employed during courtship. Male ultrasonic songs stimulate female sexual display and significantly affect mating efficiency. Considerable inter-individual differences in song structure exist. These could play a role in female mate selection provided that the females ear is able to discern them. The A. sociella mating strategy described above is unique within the subfamily Galleriinae.

Non-paraxial model for a parametric acoustic array

This study is concerned with parametric radiation from an arbitrary axisymmetric planar source with a special focus on low-frequency difference-frequency fields. As a model equation accounting for nonlinearity, diffraction, and dissipation, the Westervelt equation is used. The difference-frequency-field patterns are calculated in the quasi-linear approximation by the method of successive approximations. A multi-layer integral for calculation of the acoustic field is reduced to a three-dimensional one by employing an approximate analytical description of the primary field with the use of a multi-Gaussian beam expansion. This integral is subsequently reduced in the paraxial approximation to a one-dimensional form which has previously been published in literature and which represents a means for fast calculations of secondary acoustic fields. The three-dimensional integral is calculated numerically and the numerical results predict nonzero amplitude of the low-frequency field in the vicinity of the source which is an effect that cannot be correctly encompassed in the paraxial approximation.

Acoustic field effects on a negative corona discharge

For a negative corona discharge under atmospheric pressure in different regimes, we investigated the effects of an acoustic field both on its electrical parameters and on the change in its visual appearance. We found that the application of an acoustic field on the true corona discharge, for particular currents, decreases the discharge voltage. The application of an acoustic field on the discharge in the filamentary streamer regime substantially extends the range of currents for which the discharge voltage remains more or less constant, i.e. it allows a substantial increase in the power delivered to the discharge. The application of an acoustic field on the discharge causes the discharge to spread within the discharge chamber and consequently, a highly reactive non-equilibrium plasma is created throughout the inter-electrode space. Finally, our experimental apparatus radiates almost no acoustic energy from the discharge chamber.

Equations for description of nonlinear standing waves in constant-cross-sectioned resonators.

This work is focused on investigation of applicability of two widely used model equations for description of nonlinear standing waves in constant-cross-sectioned resonators. The investigation is based on the comparison of numerical solutions of these model equations with solutions of more accurate model equations whose validity has been verified experimentally in a number of published papers.

Ultrasonic Field Effects on Corona Discharge in Air

The application of ultrasonic waves on corona discharge causes the existence of pressure gradients in the discharge gap. According to Meeks criterion, formation of streamers in the discharge and therefore the discharge profile is affected by these pressure gradients. We calculated the distribution of ultrasonic pressure in the interelectrode gap and we demonstrated experimentally that the discharge profile is affected by this ultrasonically induced pressure distribution.

Nonlinear waves in resonators

The purpose of this paper is to find a suitable model equation for the description of finite amplitude standing waves in resonators of arbitrary axisymmetric shape filled with gas.

Optimal shaping of acoustic resonators for the generation of high-amplitude standing waves.

Within this paper, optimal shaping of acoustic resonators for the generation of high-amplitude standing waves through the use of evolutionary algorithms is discussed. The resonator shapes are described using sets of control points interconnected with cubic-splines. Positions of the control points are calculated by means of an evolutionary algorithm in order to maximize acoustic pressure amplitude at a given point of the resonator cavity. As an objective function for the optimization procedure, numerical solution of one-dimensional linear wave equation taking into account boundary-layer dissipation is used. Resonator shapes maximizing acoustic pressure amplitude are found in case of a piston, shaker, or loudspeaker driving. It is shown that the optimum resonator shapes depend on the method of driving. In all the cases, acoustic field attains higher amplitude in the optimized resonators than in simple-shaped non-optimized resonators of similar dimensions. Theoretical results are compared with experimental data in the case of a loudspeaker driving, good agreement of which is achieved.

Description of waves in inhomogeneous domains using Heun’s equation

Abstract There are a number of model equations describing electromagnetic, acoustic or quantum waves in inhomogeneous domains and some of them are of the same type from the mathematical point of view. This isomorphism enables us to use a unified approach to solving the corresponding equations. In this paper, the inhomogeneity is represented by a trigonometric spatial distribution of a parameter determining the properties of an inhomogeneous domain. From the point of view of modeling, this trigonometric parameter function can be smoothly connected to neighboring constant-parameter regions. For this type of distribution, exact local solutions of the model equations are represented by the local Heun functions. As the interval for which the solution is sought includes two regular singular points. For this reason, a method is proposed which resolves this problem only based on the local Heun functions. Further, the transfer matrix for the considered inhomogeneous domain is determined by means of the proposed method. As an example of the applicability of the presented solutions the transmission coefficient is calculated for the locally periodic structure which is given by an array of asymmetric barriers.

Numerical simulation of parametric field patterns of ultrasonic transducer arrays

The paper is concerned with numerical modeling of planar 2D ultrasonic transducer arrays for highly directional transmission of audio-frequency sound in air. The influences of the transducers arrangement in array is studied with respect to primary and secondary acoustic field patterns. The multi-Gaussian beam (MGB) model is utilized for an analytical description of the primary-wave beam, the method of successive approximations is used for quasi-linear evaluation of the self-demodulated wave pattern using only single spatial numerical integration. Simple and effective algorithm based on Evolution strategies (ES) heuristic optimization method is proposed for calculation of coefficients for MGB model expansion for arbitrary axisymmetric transducer velocity distributions.

Propagation of nonlinear acoustic plane waves in an elastic gas-filled tube

This paper deals with modeling of nonlinear plane acoustic waves propagating through an elastic tube filled with thermoviscous gas. A description of the interactions between gas and an elastic tube wall is carried out by the continuity equation of a wall velocity. Simplification on the basis of the local reaction assumption enables to model an acoustic treatment on the tube wall by using a wall impedance. Because there are considerable losses due to wall friction, the influences of the acoustic boundary layer were also considered. Using certain assumptions a special form of the Burgers equation was derived which enables to describe the propagation of nonlinear waves in the elastic tube. This model equation takes into account nonlinear, dissipative, and dispersion effects which compete each other. Characteristic lengths of the supposed effects and numerical results with respect to the source frequency were used for a qualitative analysis of the model equation. Applicability of this model equation was demonstrated by series of measurements. By application of the long-wave approximation the Korteweg-de Vries-Burgers and Kuramoto-Sivashinsky equations were derived from the modified Burgers equation.