The present study provides the first description of the calls of a multi-species ensiferan assemblage in a tropical evergreen forest of the Indian subcontinent. I have identified and described the calls of twenty ensiferan species constituting the nocturnal acoustic community of a tropical evergreen forest in KNP. I found that the multi-species ensiferan assemblage consisted of diverse taxa representing subfamilies of the families Gryllidae, Tettigoniidae and Anostostomatidae. Eight acoustically communicating species of the family Gryllidae were found. Two species belonged to the family Mogoplistidae. Interestingly, each subfamily was mostly represented by only one genus. In the tettigoniids, representative species were found only from subfamilies Pseudophyllinae, Phaneropterinae and Mecopodinae. The species richness of the acoustically communicating cricket assemblage in the tropical evergreen forest of Kudremukh was found to be low. This study did not include non-calling and ultrasonic species of crickets. The gryllid and tettigoniid species analyzed exhibited different frequency (both narrow and broadband) and temporal patterns. Species belonging to the family Gryllidae had narrow band calls (with bandwidths not greater than 1 kHz) and had dominant frequencies mainly between 3 and 7 kHz. The calls of tettigoniids covered a wide spectral range reaching far into the ultrasound in species of the genus Mecopoda. Interestingly, of nine tettigoniid species, the calls of four (Onomarchus sp., Phyllomimus sp., Brochopeplus sp. and ‘15 kHz’) were narrow band and in the audible range, similar to those of gryllids. Although there was a high overlap of call frequencies between 3 to 7 kHz, gryllid species separated in their syllable repetition rate, which varied from six syllables per second in Landreva to 60 syllables/second in Gryllitara. Species with overlapping syllable repetition rates of 10 – 20 syllables per second separated along the frequency axis. There were species such as those of Phaloria and Gryllitara, Scapsipedus, Xabea and Callogryllus that overlapped both in the spectral and syllable repetition rates. These species however, differed in the other temporal features such as call duration, call period and number of syllables per call. This study also provides the first description of the calls and stridulatory structures of an Indian weta species (Family Anostostomatidae). Both males and females of this species were found to stridulate. The calls of the two sexes had similar spectral features. Male calls consisted of four syllables each, while female calls were bisyllabic. Stridulatory structures were similar between the sexes. I also quantitatively validated the reliability of human listener - based psychoacoustic sampling as a technique to monitor species richness and relative abundance of acoustically communicating ensiferan species that are within the human hearing range. I have shown using controlled psychoacoustic tests in the laboratory that a trained listener is capable of identifying the species as well as the number of individuals of Ensifera with high accuracy. This study suggests that trained listener - based psychoacoustic sampling may be preferable to carry out rapid assessments and species inventories of gryllids and low frequency katydid species in tropical forests. My study also suggests that acoustic monitoring of Orthoptera should be done using both the trained listener - based spot sampling and ambient noise recordings using ultrasound detectors for accurately estimating species richness and relative abundance in an area. Using focal animal sampling, I have shown that most species in the tropical forest ensiferan assemblage of Kudremukh National Park did not move more than a metre in a span of half an hour. The acoustic sampling should be designed in such a way as to cause minimal disturbance to the calling animals and could be limited to ten minutes to avoid re-counting individuals and counter the problem of pseudoreplication. I also investigated the spatial dispersion of calling sites in the vertical dimension. This study revealed vertical stratification of the calling heights of the twenty ensiferan species. Calling heights of both gryllid and tettigoniid species ranged from the ground to the canopy, although more gryllid than tettigoniid species occupied the ground and herb layer. Post hoc comparisons and cluster analysis indicated the presence of discrete calling height layers corresponding to the canopy, understorey, herb and ground layer. These clusters emerged from the raw data of calling heights of individuals of each species without a priori distinction of layers. This is in contrast to other studies on vertical stratification in arthropods and bats where baits, traps and mist nets are placed at different vertical layers, thereby demarcating the layers beforehand. Previous studies on crickets, cicadas and frogs have shown preference for the height of calling sites qualitatively. To my knowledge, this is the first study to quantitatively establish vertical stratification in calling heights in an ensiferan assemblage of an evergreen forest. No correlation between the calling heights and mean dominant frequencies of the species were found. Cricket species with relatively low frequency calls (3–4 kHz) occupied both the ground layer (Callogryllus sp. and Scapsipedus sp.) and the canopy (Xabea sp. and Onomarchus sp) suggesting that these narrow-band, relatively low frequency signals may be optimal for sound transmission in the cluttered habitat of the forest floor (due to leaf litter) and the canopy (due to high leaf density). Species with high frequencies such as Brochopeplus sp. and ‘15 kHz’ called mainly from vegetation in the understorey. Species with broadband calls (Mecopoda sp., Pirmeda sp. and Elimaea sp.) called just above the ground layer and from the understorey suggesting that calls with higher frequencies and bandwidths may be used in the somewhat less-cluttered microhabitat of the understorey. Calling height stratification in the ensiferan assemblages of tropical forests could also be due to other ecological factors such as predation by spiders, mantises, bats, birds or primates. The wide range of duty cycles, presence of high duty cycle callers (such as Mecopoda) and the lack of correlation of duty cycle with calling height found in our study site are interesting. Studies on acoustic transmission in different microhabitats at different heights and on predation pressure on the ensiferan species will provide further insight into the selective forces influencing calling height stratification. The multi-species assemblage constituting the nocturnal acoustic community was found to be calling in the same time period between evening to midnight and no species was found to have a unique calling time that is different from that of another species. There was no diel partitioning of calling time between the acoustically communicating ensiferan species. Frogs and cicadas that can be considered as acoustic competitors of the ensiferan assemblage appeared to be separating from crickets on a seasonal and diel scale respectively. This study has quantified the amount of masking interference in three dimensions viz. temporal, fine temporal and spectral, between sixteen species belonging to the nocturnal acoustic ensiferan assemblage of an evergreen forest. Frequency histograms of overlap, bar graphs of overlap on a species by other species and Mantel’s test results on matrix correlation suggest negative relations between the temporal, fine-temporal and spectral overlaps. Species with high overlap in one dimension had very low levels of overlap in any of the other two dimensions, suggesting acoustic resource partitioning in the ensiferan assemblage of the evergreen forest. I also tried to quantify the extent of spatial overlap between species based on calling intensity and inter-specific distances. However, spatial overlap could not be analysed further as there were some species pairs for which I did not have the inter-individual distances despite carrying out the field work for six months. The procedure of estimating spatial overlap between species pairs and the result along with missing gaps is presented in appendix 2. It will be interesting to investigate the extent of spatial overlap between species pairs as the fourth dimension in which species could separate to avoid acoustic competition. It is also important to estimate the relative abundance of species in the evergreen forest to obtain a realistic representation of masking interference between species. Partitioning of acoustic resources among ensiferan assemblage could also be better explained by analysing all the dimensions.

Predation is a major source of mortality, resulting in strong selection on strategies to avoid being captured. Individuals have access to multiple sources of information on predation risk: they can detect danger directly themselves, and they can attend to behavioural cues or warning signals produced by others. Rapid responses are vital when hunted by aerial predators in particular, as split-second decisions can mean the difference between life and death. I studied New Holland honeyeaters, Phylidonyris novaehollandiae, as a model system to examine how alarm calls encode information about danger and to understand how this information is used by receivers. In Chapter 2, observational data showed that these honeyeaters produce multi-element, aerial alarm calls in response to flying threats. Male honeyeaters had more opportunities to detect threats than did females and showed a greater propensity to alarm call when presented with gliding model predators. In Chapter 3, a combination of observational data and model presentations demonstrated that aerial alarm calls encode urgency in both the number of elements, with more dangerous threats receiving more elements, and the acoustic structure of the first element. Playback presentations of alarm calls and video recordings to measure responses revealed that honeyeaters made extremely fast decisions about fleeing to cover based on the acoustic structure of the first alarm element, while the number of elements determined for how long they hid. These two chapters demonstrate that receivers have rapid access to detailed information about the type and degree of danger from conspecific alarm calls. In Chapter 4, I investigated how birds integrate personal information about danger with social information from alarm calls. Perched birds were faster to detect model predators than feeding birds, suggesting that they have greater access to personal information. Consistent with this, perched birds were less likely to flee to cover in response to alarm playbacks than foraging birds. Birds also fled less in response to less urgent social information, such as playbacks of more distant alarm calls, and less relevant social information, in the form of calls from another species with overlapping but not identical threats. In Chapter 5, I tested how honeyeaters value social information about danger derived from single versus multiple sources, both within and across species. Birds paid attention to the number of independent signallers when assessing information from both conspecifics and heterospecifics, responding more strongly to playbacks of alarm calls from two sources than a single source, but they also moderated their responses according to signal relevance. Together, these results show that birds make flexible decisions about danger by integrating information from multiple sources and assessing its quality, allowing them to mitigate the costs of fleeing to false, or irrelevant, alarms while taking advantage of the multitude of information provided by the prey community's neighbourhood watch.

The investigation of a species’ repertoire and the contexts in which different calls are used is central to understanding vocal communication among animals. Beluga whale, Delphinapterus leucas, calls were classified and described in association with behaviours, from recordings collected in the Churchill River, Manitoba, during the summers of 2006-2008. Calls were subjectively classified based on sound and visual analysis into whistles (64.2% of total calls; 22 call types), pulsed or noisy calls (25.9%; 15 call types), and combined calls (9.9%; seven types). A hierarchical cluster analysis, using six call measurements as variables, separated whistles into 12 groups and results were compared to subjective classification. Beluga calls associated with social interactions, travelling, feeding, and interactions with the boat were described. Call type percentages, relative proportions of different whistle contours (shapes), average frequency, and call duration varied with behaviour. Generally, higher percentages of whistles, more broadband pulsed and noisy calls, and shorter calls (<0.49s) were produced during behaviours associated with higher levels of activity and/or apparent arousal. Information on call types, call characteristics, and behavioural context of calls can be used for automated detection and classification methods and in future studies on call meaning and function.

The investigation of a species’ repertoire and the contexts in which different calls are used is central to understanding vocal communication among animals. Beluga whale, Delphinapterus leucas, calls were classified and described in association with behaviours, from recordings collected in the Churchill River, Manitoba, during the summers of 2006-2008. Calls were subjectively classified based on sound and visual analysis into whistles (64.2% of total calls; 22 call types), pulsed or noisy calls (25.9%; 15 call types), and combined calls (9.9%; seven types). A hierarchical cluster analysis, using six call measurements as variables, separated whistles into 12 groups and results were compared to subjective classification. Beluga calls associated with social interactions, travelling, feeding, and interactions with the boat were described. Call type percentages, relative proportions of different whistle contours (shapes), average frequency, and call duration varied with behaviour. Generally, higher percentages of whistles, more broadband pulsed and noisy calls, and shorter calls (<0.49s) were produced during behaviours associated with higher levels of activity and/or apparent arousal. Information on call types, call characteristics, and behavioural context of calls can be used for automated detection and classification methods and in future studies on call meaning and function.

Masters of Science / Although the processes that promote biodiversity and speciation remain poorly understood, ecological factors are thought to be one of the causal agents responsible for promoting variation. Bladder grasshoppers (Orthoptera; Pneumoroidea) are a group of endemic southern African insects that provide an ideal model system to study the role of ecology in speciation. All species rely on acoustic communication for mate location, with males producing an extremely loud advertisement call that is highly species specific. Any alteration to the male call would thus likely have implications for species integrity. In this study, I examined geographic variation as well as potential ecological drivers of biological diversity within Bullacris unicolor, a variable and wide-ranging species of bladder grasshopper. The main aims of the study were to characterise the extent of acoustic and morphological variation among individuals sampled from five geographic locations and to correlate this variation with environmental data and host plant use. At the inter-population level, I found significant differences between populations with respect to both morphological and acoustic characters. Results of multivariate analyses showed significant differences in the body length, pronotum length and head width of males and in the pronotum length, abdomen width and head width of females. Similarly, the acoustic signals of males from the five populations differed significantly in both temporal and frequency components, with all but one variable (peak frequency of the introductory syllables) showing a significant difference. However, there was no correlation between morphological and acoustic variables among populations, and acoustic characters showed far greater divergence among populations than did morphology. In both males and females, the morphological variables that differed among populations were negatively correlated with mean annual temperature, indicating that grasshoppers are larger in areas with lower temperatures. Also, some of the call characteristics of males were correlated with temperature, precipitation, altitude, and slope. Although grasshoppers were observed feeding on a range of host plant species, neither morphology nor signal characteristics were found to vary according to host plant. At the intra-population level, multivariate analyses revealed that all acoustic characters differed significantly among individuals. Morphology may be influencing signal properties within a population to some extent as there were significant correlations between some of the call characters and both abdomen width and tibia length, with lengths of these two morphological variables being positively correlated with temporal components of the call and abdomen width being negatively correlated with frequency components. I also found a significant difference in the carrier frequency of male calls, as well as in some of the morphological characters of males and females, according to host plant. This indicates that host plant use has a greater effect on variation at the intra-population level than at the interpopulation level. In conclusion, the results of my study reveal significant variation in the morphology and acoustic signals of B. unicolor, both within and among populations, and suggest that this variation is at least partially related to ecological factors.

This was a thesis that was commissioned by Researcher Peter Sigray at the Royal Institute of Technology (KTH) in Stockholm and was based on an idea by Professor Thomas Rossby, University of Rhode Island (URI). The idea was to further develop the existing Expendable Bathythermograph (XBT), which has been in use since the 1960s. This by first and foremost replacing existing transfer technology, which involved using a thin copper wire when communicating with the recipient remaining on the ship. The new way in which communication is to take place, is by acoustic signals transmitted from the freely descending probe. The goal is to be able to measure down to greater depth compared to the previous type. The aim is to increase today's in-depth measuring capacity of about 900 meters, down to depth of at least 2000 meters, preferably even deeper. The thesis project was divided into several smaller parts, some of which went on in parallel, while others had to have the preceding portion completed, in order for them to take place, i.e., to begin. Initially – and in parallel during the rest of the thesis work – their were studies of two selected books and a set of documents. This to ensure the understanding of all the concepts to be used during the development of the probe. In parallel with the studies, simulations in the computer program COMSOL Multiphysics began. The model probe geometry and material parameters were programmed. An important task was to implement and verify that the so called Perfectly Matched Layer (PML) performed as expected. This was of crucial importance, as different implementations of the PML turned out to result in different outcomes of the simulations’ data. With the results from Perfectly Matched Layer tests verified, the actual simulations could be initiated. Two different pipes were evaluated; one made of stainless steel and the other made of aluminum alloy. Their proportions were slightly different regarding diameter and length. The simulations led to the makings of plots/diagrams over the Transmission Voltage Response (TVR) over a certain frequency range (3000-17000 Hz). Directivity polar plots were also created for both pipes in the program MATLAB and by using a MATLAB. The actual assessment of the probes began in the latter part of the simulation work. There were several different steps in the process of assembling the probes. Finally, the tests in the water tank at The Defense Research Institute (FOI) could take place. For three days all the simulated results were “put to test.” The results during the tests in the water tank at FOI were promising and the remaining challenges, before a complete probe is developed, are achievable. The hypothesis that initially was set got proven, and it can be argued that the thesis as a whole successfully demonstrated it to be true. The idea of the probe is definitely worth further development, in the making of the new version of the Expendable Bathythermograph.

Underwater robotic vehicles are used in a variety of environments that would be dangerous for humans. For these vehicles to be successful, they need to be tolerant of a variety of internal and external faults. To be resilient to internal faults, the system must be capable of determining the source of faulty behavior. However many different faults within a robotic vehicle can create identical faulty behavior, which makes the vehicles impossible to diagnose using conventional methods. I propose a novel active diagnosis method for differentiating between faults that would otherwise have identical behavior. I apply this method to a communication system and a power distribution system in a robotic vehicle and show that active diagnosis is successful in diagnosing partially observable faults. An example of an external fault is inter-robot communication in underwater robotics. The primary communication method for underwater vehicles is acoustic communication which relies heavily on line-of-sight tracking and range. This can cause severe packet loss between agents when a vehicle is operating around obstacles. I propose novel path-planning methods for an Autonomous Underwater Vehicle (AUV) that ferries messages between agents. I applied this method to a custom underwater simulator and illustrate how it can be used to preserve at least twice as many packets sent between agents than would be obtained using conventional methods.

Wireless Sensor Networks (WSNs) has become increasingly important in the Oil and Gas industry. Despite the various advantages WSN has compared to the wired counter parts, it also faces some critical challenges in the oil fields; one of them is the power supply. The periodic replacement of batteries for the WSN in the downhole environments has been economically inconvenient and the enormous cost induced by the maintenance has turned people's attention to the energy harvesting technology, hoping for a more sustainable solution. Power supply is only half of the problem. To retrieve the data recorded by the various sensors in the downhole environments, a reliable way of wireless communication is required. A new approach utilizing acoustic communication was proposed. This thesis presents an Archimedean Screw Turbine (AST) based energy harvester that takes advantage of the abundant flow energy in the upper stream section of the oil production cycle, especially in the water injection wells and oil extraction wells, with the goal of providing power supply to Wireless Sensor Networks (WSNs) and underwater acoustic modems deployed in the various locations in the downhole environments. Parametric study on the number of blades, screw length, screw pitch, and rotational speed was conducted through CFD analysis using Ansys Fluent in order to determine the optimal geometry and operating conditions. The relationship between power generation and AST geometries, such as AST length and AST pitch, were discovered and the optimal rotational speed was revealed to be solely dependent on the screw pitch. Experiments were conducted in the lab environment with various flow rates and various external resistive loads to verify and determine the maximum power generation of the designed harvester. FEA analysis was conducted using the Acoustic and Structural Interaction Module of COMSOL MULTIPHYSICS to determine the attenuation characteristics of acoustic waves propagating in the water-filled pipes buried in soil. Experiments with and without the harvester integrated in the pipe system were conducted in lab environment using a pair of under water acoustic modems to determine the acoustic communication capability. The impact of the integrated harvester on the acoustic communication was tested. Combining energy harvesting technology and underwater acoustic communication together, this system can potentially achieve real-time monitoring and communication in the oil downhole environment. / Master of Science / Oil and Gas industry has been the primary energy source provider for our society for hundreds of years. As this industry evolves with new technologies, it also faces new challenges. One of the main challenges is the power supply problem in the oil field because of the limited lifespan of traditional batteries used in the oil production process. This study present a novel energy harvesting device that can replace the traditional batteries. By taking advantage of the constant fluid flow in various wells at oil field, the device can provide power for electronic devices, including but not limited to wireless sensors, communication modules, at the oil extraction sites, without needing additional power supply. This novel energy harvesting device can also be integrated with communication modules that uses acoustic wave to achieve wireless acoustic communication between underground and the surface. In this study, the harvester design, optimization, tests, and integration with acoustic modems were presented. With the help of such energy harvesting device, Oil and Gas industry will be one step closer to achieving true wireless, and real-time monitoring and communication. This will not only reduce maintenance cost but also greatly improve the production efficiency.

No description available.

The thesis deals with vocalizations produced by Eurasian ground squirrels of the genus Spermophilus. It is mainly focused on inter-species and intra-species variability in acoustic structure of alarm calls which are emitted in presence of predators.The major part of the thesis deals with intra-species variability in acoustic structure of the alarm calls in five Eurasian ground squirrels, Spermophilus citellus, S. taurensis, S. xanthoprymnus, S. suslicus and S. fulvus. It has been confirmed that the alarm calls of these ground squirrels show a high level of species specificity. The thesis further describes another vocalizations produced by three Eurasian ground squirrel species, Spermophilus suslicus, S. citellus and S. fulvus, and shows that with the exception of the alarm calls, vocal repertoires of these three ground squirrels are remarkably similar. The last part of the thesis deals with individual distinctiveness of the alarm calls of three Eurasian ground squirrels, Spermophilus citellus, S. taurensis and S. xanthoprymnus. It has been shown that the alarm calls of these species have a significant potential to encode information about caller identity.