This study addresses the detection of multiple objects in acoustic image. A fast two‐dimensional (2D) subset censored constant false alarm rate (CFAR) method is proposed. The proposed method uses a multi‐subset sliding window with reference cells and guard cells in 2D, and excludes the potential interference object by subset censoring. Specifically, the reference cells are equally divided into four subsets, the subset with the largest summation is censored, and the remaining subsets are used to calculate the local threshold. A fast algorithm based on integral image is employed for lowering computational load. It requires only 32 operations for a single test cell averagely, despite the total number of reference cells. The proposed method is assessed on real multi‐beam acoustic image sequences, of which the background follows a distribution of Weibull. Experimental results are compared with the results acquired from the method including cell averaging CFAR and censored mean‐level detector CFAR in 2D. The proposed method has been proved to be efficient and robust in multi‐object environment, especially as multiple objects placed closely.

Backscattered sound waves of seabed sediments are important information carriers in seafloor detection and acoustic characteristic parameters inversion. Most of the existing methods for estimating geoacoustic parameters are based on multiangle seabed backscattered signal processing and suitable for flat seafloor conditions with uniform sediment thickness. This usually deviates from the real field conditions and affects the accuracy of parameter estimation. In this paper, the sound ray propagation theory is studied and analysed under the condition of sloping seabed and uneven sediment thickness. Based on the phased parameter array sonar system, a method of acoustic parameters estimation of the sediment under inclined seabed conditions is proposed. The simulation results show that the new method shows good adaptability to different inclination angles of the seabed and solves the problem of accuracy of acoustic parameter estimation of the inclined seabed sediments. The model will greatly reduce the seafloor topography requirements in the sediment acoustic parameter inversion, such as velocity, layer thickness, and acoustic impedance.

A series of fluorescence lifetime fitting algorithms are discussed and compared. A Fiber Optical thermometer based on DSP technique is proposed to realize an original estimation algorithm - FFT method.

The spatial distribution of bubble liquids strongly affect linear-wave propagation in bubbly liquids. The classical understanding suggests that using positional correlations of the bubbles, such as “hole correction” or Perkus-Yevick approximation, describes the spatial information of bubble clouds. However, bubbly liquids are observed experimentally with complex bubble ensembles that take the form of clusters, filaments, and clouds which cannot be intuitively described by these pair-correlation functions and need to be better clarified. To achieve this purpose, a three-dimensional random model, the Neyman-Scott point process, is proposed to describe bubbly liquids with clustering. Base on this method, we study the influence of such phenomenon on acoustic dispersion and attenuation relations. A formula for effective wavenumber in bubbly liquids is derived, based on self-consistent method. Comparing with the equation of Commander and Prosperetti [J. Acoust. Soc. Am. 85, 732 (1989)], our results show that the clustering can suppress peaks in the attenuation and the phase velocity as functions of the frequency. Further, we provide a numerical simulated method. A clustered bubbly liquid is simulated with strict mathematical method and the statistical informations are obtained through unbiased statistical approach. Through the results, we quantificationally analyze the influence of estimated value on predictions.