Chong Wei

Curtin University · Centre for Marine Science and Technology (CMST)

The reconstruction of the acoustic properties of a neonate finless porpoise's head was performed using X-ray computed tomography (CT). The head of the deceased neonate porpoise was also segmented across the body axis and cut into slices. The averaged sound velocity and density were measured, and the Hounsfield units (HU) of the corresponding slices...

The relative role of the various structures in the head of the baiji (Lipotes vexillifer) is examined. A finite element approach was applied to numerically simulate the acoustic propagation through a dolphin's head to examine the relative role of the skull, air sacs, and melon in the formation of the biosonar beam in the vertical plane. The be...

Rotational behaviour has been observed when dolphins track or detect targets, however, its role in echolocation is unknown. We used computed tomography (CT) data of one live and one recently deceased bottlenose dolphin together with measurements of the acoustic properties of head tissues to perform acoustic property reconstruction. The anatomical c...

The Risso’s dolphin (Grampus griseus) has a distinctive vertical crease (or cleft) along the anterior surface of the forehead. Previous studies have speculated that the cleft may contribute to biosonar beam formation. To explore this, we constructed 2D finite element models based on computer tomography data of the head of a naturally deceased Risso...

No PDF available ABSTRACT Spinning is a natural and common dolphin behavior; however, its role in echolocation is unknown. We used computed tomography (CT) data of a live and a recently deceased bottlenose dolphin together with measurements of the acoustic properties of head tissues to perform acoustic property reconstrcution. The anatomical config...

Dolphins use their biosonar to discriminate objects with different features through the returning echoes. Cross-modal matching experiments were conducted with a resident bottlenose dolphin ( Tursiops aduncus ). Four types of objects composed of different materials (water-filled PVC pipes, air-filled PVC pipes, foam ball arrays, and PVC pipes wrappe...

As a member of Sciaenidae, Chinese bahaba (Bahaba taipingensis) generate sounds using sonic muscles to drive the swim bladder. In this study, the drumming sounds of Chinese bahaba in two groups differing in body size were recorded in an indoor aquarium and an outdoor pond. A piecewise exponential oscillation function was developed to synthesize the...

Marine mammals in the cetacean order are the whales, dolphins, and porpoises and are separated into two groups or suborders: toothed whales (Odontocetes) and baleen whales (Mysticetes). They have complex acoustic repertoires comprising several major types of vocalizations for communication, navigation, foraging for prey, group cohesion, and avoidin...

Echolocation signals emitted by odontocetes can be roughly classified into three broad categories: broadband echolocation signals, narrowband high-frequency echolocation signals, and frequency modulated clicks. Previous measurements of broadband echolocation signal propagation in the bottlenose dolphin (Tursiops truncatus) did not find any evidence...

In 1974, Norris and Harvey measured the sound velocity profile of the melon of a just deceased bottlenose dolphin and found a low-velocity core in the melon with the velocity increasing towards the surface. This was the genesis of the “melon focusing” hypothesis in the formation of the biosonar beam. Aroyan solved the wave equation for a signal pro...

The echolocation signals emitted by odontocetes can be roughly classified into three broad categories: broadband high-frequency echolocation signals, narrowband high-frequency echolocation signals, and frequency modulated clicks. Previous measurements of broadband echolocation signals propagation in the bottlenose dolphin (Tursiops truncatus) did n...

Research into the physical mechanism of odontocetes biosonar has made great progress in the past several decades, especially on wave propagation and biosonar beam formation in the foreheads of odontocetes. Although a number of experimental studies have been performed, the physical mechanism of odontocetes underwater target discrimination has not ye...

Atlantic bottlenose dolphins (Tursiops truncatus) can effectively discriminate between water-filled cylinders with different wall thicknesses. The dolphins' performance may be particularly good when the cylinders are thinner. The dolphins' performance is also asymmetric, in that the discrimination accuracy is not equal when the target thickness inc...

Yangtze finless porpoises (Neophocaena asiaeorientalis) are known to use the narrowband signals for echolocation. In this study, a finite-element model was configured based on computed tomography imaging technique and tissue physical properties measurement to simulate biosonar signal emission and transmission processes through animal’s head. The ro...

Bottlenose dolphins project broadband echolocation signals for detecting and locating prey and predators, and for spatial orientation. There are many unknowns concerning the specifics of biosonar signal production and propagation in the head of dolphins and this manuscript represents an effort to address this topic. A two-dimensional finite element...

Yangtze finless porpoises (Neophocaena asiaeorientalis) are known to use the narrowband signals for echolocation. In this study, a finite-element model was configured based on computed tomography imaging technique and tissue physical properties measurement to simulate biosonar signal emission and transmission processes through animal’s head. The ro...

A finite element method was used to investigate the temperature influence on sound beams of the Indo-Pacific humpback dolphin. The numerical models of a dolphin, which originated from previous computed tomography (CT) scanning and physical measurement results, were used to investigate sound beam patterns of the dolphin in temperatures from 21 °C to...

Dolphins and porpoises use their sophisticated biosonar systems for targets detection, within a range of a few meters to about 200 m, there is not a better sonar on the planet. In this study, the high resolution computer tomography (CT) scan data were used to create the detecting click signal propagation models of Atlantic bottlenose dolphins (Turs...

Harbor porpoises (Phocoena phocoena) use narrow band echolocationsignals for detecting and locating prey and for spatial orientation. In this study, acoustic impedance values of tissues in the porpoise's head were calculated from computer tomography(CT) scan and the corresponding Hounsfield Units. A two-dimensional finite element model of the acous...

Computed tomography (CT) imaging and ultrasound experimental measurements were combined to reconstruct the acoustic properties (density, velocity, and impedance) of the head from a deceased Indo-Pacific humpback dolphin (Sousa chinensis). The authors extracted 42 soft forehead tissue samples to estimate the sound velocity and density properties at...

Vocalizations of a wild finless porpoise (Neophocaena asiaeorientalis sunmeri) were recorded within the dolphin natural reserve, in the western coast of the Taiwan Strait, China. The subsequent acoustical analyses suggested that the porpoise (N. p. sunameri) produced typical phocoenid clicks, with the peak frequency ranging from 123.4 to 141.4 kHz,...

Computed tomography (CT) imaging and ultrasound experimental measurements were used to reconstruct the acoustic properties (density, velocity, and impedance) of forehead tissues from a deceased Indo-Pacific humpback dolphin (Sousa chinensis). The nonlinear regression methods were used to demonstrate the relationships between the sound velocity and...

Porpoises are well known to emit directional ultrasound beams for detecting and tracking preys; however, how they produce and manipulate directional beams are challenging. Here, we investigated physical mechanism of ultrasound beam formation and control of finless porpoise (N. a. sunameri) by using an integrated scheme of computed tomography, tissu...

Bottlenose dolphins (Tursiops aduncus) are a well-known species using broadband echolocation signals for searching prey and spatial orientation. In this study, the computed tomography (CT) scan data were obtained to set up a two-dimensional finite element model. In the vertical plane, the acoustic field on the animal’s forehead and the far field tr...

Computed tomography (CT) was used to compare the tissue structures involved in sound production and reception in a fetus and its maternal body of a female finless porpoise (Neophocaena asiaorientalis sunameri) found stranded at Huian, Fujian Province, China, in April 2014. Qualitative assessment of the CT images revealed the physical development of...

To automatically classify bottlenose dolphin's whistles, a method, which is based on syntactic pattern recognition, is presented. Dolphin whistles have typically been characterized in terms of their instantaneous frequency as a function of time, which is also known as "whistle contour". The frequency variation feature of a dolphin whistle is extrac...

Through numerically solving the appropriate wave equations, propagation of biosonar signals in a Chinese river dolphin (baiji) was studied. The interfacial waves along the rostrum-tissue interfaces, including both compressional (longitudinal) and shear (transverse) waves in the solid rostrum through fluid-solid coupling were examined. The baiji's r...

The Indo-Pacific humpback dolphin (Sousa chinensis), is believed to use sophisticated bio-sonar for navigation, orientation and foraging. Acoustic properties of its head have not yet been studied and are essential to study the dolphin biosonar system. In this paper, sound velocity distribution of an Indo-Pacific humpback dolphin head was reconstruc...

New data have significantly increased our understanding of sound propagation within the heads of dolphins. Results of Au et al. (2016) reinforce the notion that source intensity is the primary factor controlling the peak and center frequencies of biosonar clicks which in turn affects the duration and the bandwidth of clicks. Finite element simulati...

Harbor porpoises (Phocoena phocoena) use narrow band echolocation signals for locating prey and spatial orientation. In this study, acoustic impedance values of tissues in the porpoise’s head were calculated from the Hounsfield Units (HU). A two-dimensional finite element model was set up base on the computed tomography (CT) scan data to simulate t...

Finless porpoise (Neophocaena asiaeorientalis) is known to use the narrow band signals for echolocation living in the Yangtze River and in the adjoining Poyang and Dongting Lakes in China. In this study, the sound velocity and density of different tissues (including melon, muscle, bony structure, connective tissues, blubber, and mandibular fat) in...

The baiji (Lipotes vexillifer) of the Yangtze River possesses a sophisticated biosonar system. In this study, a finite element approach was used to numerically investigate the propagation of acoustic waves through the head of the Yangtze River dolphin, which possesses an inhomogeneous and complex structure. The acoustic intensity distribution predi...

This study compared the whistles recorded from captive bottlenose dolphins (Tursiops truncatus) under two different experimental conditions (swimming and training) based on the signals' frequency characteristics, and the t-test was applied for statistical analysis. The results showed that most of the signals were the sine category when the dolphins...

The melon of dolphins is considered by many as the structure responsible for the focusing of the biosonar beam. However, finite element numerical simulation of the head of the Chinese river dolphin (Lipotes vexillifer) indicates that the biosonar beam is formed by reflections off the airsacs and bony structures in the skull. The finite element appr...

This study performs the quantitative analysis and comparison to acoustic signal characteristics of Large Yellow Croaker (Pseudosciaena crocea) at two different ages. The sounds were recorded from the fishes in a net-cage. Two exponential oscillation functions are built to fit the acoustic signal of the fishes. The signal characteristic of the oscil...

Whistles play an important role in Indo-Pacific humpback dolphins' social interactions, and function as individual identifiers. Therefore the investigation of their whistles will be beneficial for acoustic monitoring and for estimating their seasonal occurrence and abundance, which will be one of the very basic requirements for successful managemen...