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• Explosive sound source positioning by using modified Levenberg Marquardt algorithm. • A comparative analysis of different positioning methods. • Modified LMA performance validation through simulation and experimental studies. • A short and wide range of sound source positioning by varying r between 0.002 and 2. • Sound source localization for both indoor and outdoor environments. In this paper, a modified Levenberg-Marquardt algorithm (MLMA) is proposed to localize the 'point of burst' of an explosive sound source over the range of (0.5–2500) m. The objective function for minimization is formulated through the time difference of arrival based multilateration approach. The developed method uses four exclusive steps to satisfy global convergence along with fast computational speed. The performance of the proposed method is validated through both indoor-outdoor experiments and simulation studies and compared to other well-known methods. The experimental results show that the non-iterative approaches perform satisfactorily only if the ratio of microphone spacing to source range r is greater than 0.30. However, the iterative approaches outperform non-iterative approaches for any r. It is also observed that the MLMA converges globally at least five times faster than other algorithms. The numerical simulation results also demonstrate that the MLMA provides optimal solutions at lower and higher noise thresholds. [ABSTRACT FROM AUTHOR]

Abstract: Time varying frictional torque is one of the principal exciting sources of vibration in gears. A number of literature have already been devoted to find an expression for time-varying frictional torque for helical and spur gears. For helical gears, time-varying contact length excites a number of other time-varying parameters such as mesh stiffness, damping coefficient, and frictional force and torque which subsequently give rise to time-varying bending moment and bearing force. Hence an elaborate review of time-varying contact length, and frictional force and torque is covered in this paper. A new approach and algorithm to find frictional torque for investigation of torsional vibration of helical gear system has been suggested. [Copyright &y& Elsevier]