Acoustical Physics最新文献

Acoustic attenuation coefficient per unit frequency square has been calculated for pure semiconductors like silicon and germanium, as well as for mixed semiconductors like gallium arsenide (III–V group) and tin telluride (IV–VI group), for longitudinal waves travelling along the (leftlangle {100} rightrangle ) crystallographic axis, within the temperature range 80–300 K. Second-order elastic constants of the materials are used to calculate the average Gruneisen parameter (leftlangle {{{gamma }}_{i}^{j}} rightrangle ), using which the nonlinearity parameter D_L has been calculated for different temperatures. The knowledge of D_L is used for calculation of acoustic attenuation coefficient per unit frequency square due to phonon–phonon interaction ({{left[ {{{{alpha }} mathord{left/ {vphantom {{{alpha }} {{{f}^{2}}}}} right. kern-0em} {{{f}^{2}}}}} right]}_{{text{L}}}}) and thermoelastic losses ({{left[ {{{{alpha }} mathord{left/ {vphantom {{{alpha }} {{{f}^{2}}}}} right. kern-0em} {{{f}^{2}}}}} right]}_{{{text{th}}}}}). Acoustic attenuations are found to be temperature dependent and increases with it. The magnitude of acoustic attenuation per unit frequency square due to phonon–phonon interactions is greater than that due to thermoelastic losses. The magnitude of acoustic attenuation for the investigated semiconductors is in the order Si < Ge < GaAs < SnTe. It is observed that anharmonicity of the solids which give rise to phonon–phonon interaction is the dominant cause of acoustic attenuation of propagating waves. The acoustic attenuation of propagating waves is found to be proportional to the molecular weights of semiconductors.

The paper unwraps the potential application of graph features through complex network analysis in assessing the tone quality of a musical note by analysing the two notes, C and G, at different octaves played by the wind instruments, flute and trumpet, as examples. The musical note sound signals are subjected to fast Fourier transform and wavelet analyses to understand harmonic content and its sustainability. The complex network generated from the temporal data helps in understanding the airflow dynamics through the graph features—edge count, graph density and transitivity. The study reveals that the greater the value of network features, the lesser the overtones present in the musical note, suggesting its application in assessing the musical tone quality or timbre.

The possibility of evaluating the quality of thermal diffusion welding of two yttrium aluminum garnet crystals in a composite optical disk has been studied using the optoacoustic method. To obtain acoustic images of thermal diffusion welding, an optoacoustic transducer connected through an optical fiber with a pulsed laser (wavelength of 532 nm, pulse duration of 10 ns) were used for scanning over the disk surface. The ultrasonic pulses in the frequency range up to 80 MHz are recorded simultaneously with movement of the transducer over an area of 16×16 mm with a step of 0.1 mm. Two ultrasonic scanning modes were used: forward and backward. The 15-mm-diameter composite disks with different quality of thermal diffusion welding were tested. The possibility of quantifying the quality of the diffusion layer using an optoacoustic method for objective comparison of the disks is discussed. The obtained data are confirmed by the results of measurements using an optical projection method.

Beside the numerous applications obtained by the interaction of a laser beam with acoustic waves, another application have recently emerged that allows generating an optical dynamic spatial array (ODSA) using two orthogonal acoustic waves. In this paper, we demonstrate theoretically and illustrate numerically the possibility of generating an ODSA composed of many diffracted orders. The obtained results show that each diffracted order navigates in space according to its own trajectory and its own velocity. These trajectories are sometimes linear with sinusoidal velocities, sometimes circular with constant velocities and often elliptical with variable velocities. Moreover, the high diffracted orders of this ODSA, which are characterized by a high velocity and a large scanned area, can be controlled by varying the Raman–Nath parameter. The outstanding point is that all these diffracted orders navigate in space with the same sweep frequency despite the diversity of trajectories and velocities. The borrowing of Poincaré and Bloch spheres allows enumerating all these trajectories and presenting them in an elegant and attractive method. This technique can be used in metrology for rotation measurements based on Doppler effect. In addition, we can used it to develop a spatial display allows tracing Lissajous trajectories rather than using an oscilloscope.

The acousto-optic characteristics of a paratellurite crystal with a cut angle of α = 10.2° have been investigated theoretically and experimentally. The crystal is used in an acousto-optic filter for processing optical images in visible and infrared light. The electric range of filter tuning has been experimentally determined based on the frequency dependence of the power absorbed by the piezoelectric transducer of the filter. Estimates of the range of filter tuning with respect to optical wavelengths are made. At light wavelengths of λ = 1.15 µm and λ = 0.63 µm, the dependences of the Bragg angle of incidence on the ultrasound frequency are calculated. When measuring the diffraction efficiency in the deflector operation mode, it was found that the range of filter tuning in optical wavelengths turns out to be different from that predicted as a result of measuring the electrical characteristics of the transducer and becomes narrower.