The exact solutions for rays and ray tube areas in a standard atmosphere made it possible to formulate a criterion for sonic boom focusing on the ground in supersonic turn mode, as well as to calculate the caustic–ground intersection line width in acceleration mode in elementary functions. The dichotomy method was used as the basis for simple algorithms to calculate the caustic–ground intersection lines (focusing lines) arising in the acceleration and supersonic turn modes of a supersonic passenger aircraft. The dependence of the geometry of the focusing lines on the main flight trajectory parameters has been investigated. In acceleration mode, these parameters are flight altitude and acceleration, and in the case of supersonic turn, flight altitude, Mach number, and trajectory curvature radius. The focusing lines “stabilization” effect with increasing acceleration in acceleration mode and Mach number in supersonic turn mode has been observed. It has been established that flight altitude has a significantly smaller effect on the focusing lines shape than other trajectory parameters.
Sound source identification based on the temporal realization of the signal is a pressing problem for various practical applications, ranging from speech recognition to vibration defect diagnostics. This paper proposes a classification algorithm based on modern convolutional neural networks. The input data is a log-mel spectrogram obtained by multitaper processing—a power spectrum estimation method that uses orthogonal windows (tapers) to suppress noise components and improve the information content of features. Multitaper processing allows one to estimate the power spectral density of a stationary ergodic random process using a finite segment of its realization. The mel scale is a psychophysical pitch scale that simulates human perception. This paper presents a description of the algorithm and its validation using river navigation data collected using a directional sound source—a microphone located in the focal plane of a parabolic reflector. Model training is evaluated depending on the amount of data, and the performance of various convolutional networks is compared.
The article presents the results of a study of the acoustic parameters of a vocal source and the dynamics of the glottis area under terrestrial gravity and weightlessness. Vocal source pulses are found by inverse filtering of the speech signal using the linear prediction method. The glottis area function is determined as the solution to the inverse problem for the equation of airflow through the glottis. The extrema of the vocal excitation impulse and its integral, as well as the extrema of the glottal area function and its time derivative, are calculated. The temporal relationships between these extrema are determined in speech tests recorded under gravity and weightlessness. Four cosmonauts participated in the speech experiments. The effect of weightlessness on the probability distribution of the calculated parameters was determined. The quantitative indicators of these discrepancies depend on the speaker and the phonetic composition of the speech tests.
Based on spatial acoustic measurements carried out on the relatively shallow northeastern shelf off Sakhalin Island during seismic surveys, estimates of the horizontal directivity pattern of the seismic vessel’s source array were constructed at distances of 1.2, 2.4, and 4.6 km in three frequency bands: 10–350, 10–70, and 70–350 Hz. The estimation methodology measures the energy of seismoacoustic pulse signals propagating in the water column along a series of acoustic paths with nearly identical seabed profiles. In the 70–350 Hz band, signal energy is primarily carried by water-column normal modes, and the resulting directivity pattern exhibits clear directionality closely matching the theoretical pattern calculated for deep-water conditions. In the low-frequency band (10–70 Hz), the directivity pattern shows no dependence on the azimuthal angle. Both experimental and theoretical analyses demonstrate that estimation of the directivity pattern in the 10–70 Hz band may be inaccurate when there are spatial heterogeneities in the seabed, specifically variations in the compressional-wave speed . These findings are directly relevant to assessing the acoustic impact of seismic surveys in coastal shelf regions.
Using numerical simulation, error estimates for acoustic methods of distance measurement to underwater vehicles in the southern part of the Kara Sea have been obtained. Trains of soliton-like internal waves (IWs), which may occur on the acoustic path between an acoustic beacon and an underwater vehicle equipped with a navigation sound receiver, are considered the primary factor determining the errors in such measurements. According to experimental data, the amplitude of solitons in a train in the study area can reach several tens of meters, with the phase front width of the IWs exceeding 10 km. It is demonstrated that these hydrodynamic disturbances can lead to measurement errors of up to hundreds of meters, depending on the direction of propagation of the IW train: along or across the acoustic path.
