Spatio-temporal variation in activation rates during ventricular fibrillation (VF)provides insight into mechanisms of sustained re-entry during VF. This study had three objectives related to spatio-temporal dynamics in activation rates during VF. The first objective was to quantify spatio-temporal variability in activation rates,that is, in dominant frequencies, computed from epicardial electrograms recorded during VF in swine. Results showed that temporally and spatially, dominant frequencies variedas much as 20% of the mean dominant frequency, and the mean dominant frequencies increased during first 30 sec of VF. These results suggest that activation rates are nonstationary during VF. The second objective of the study was to develop a new stimulation protocol for quantifying restitution of action potential duration (APD) by independently controlling diastolic intervals (DI). A property of cardiac cells that determines spatio-temporal variability in dominant frequencies is restitution of APD, which relates APD to the previous DI. Independent control of DI permits explicit determination of the role of memory in restitution. Restitution functions quantified using mathematical models of activation and our stimulation protocol, showed significant hysteresis. That is, for adiastolic interval, the action potential durations were as much as 15% longer during periods when the DI were decreasing than when the DI were increasing. We verified the feasibility of implementing our protocol experimentally in isolated and perfused rat hearts with action potentials recorded using floating glass microelectrodes. The third objective of our study was to verify that spatio-temporal variability in dominant frequencies during VF could be modified using spatially distributed pacing strength stimuli. Simulated VF was induced in 400x400 and 400x800 matrices of cells. Electrical function of cells was simulated using the Luo-Rudy model. Stimulators were arranged in the matrices such that there were 5 rows of line stimulators. Results showed that it was possible to modify activations in almost 54% of the area and to modify spatio-temporal variability in activation during VF into a desired pattern by the use of synchronized pacing from multiple sites. These results support further exploration of distributed stimulation approach for potential improvements in defibrillation therapy.

This thesis studies structural dynamic system identification in a frequency-based framework. The basic consideration stems from the fact that frequencies may generally be measured with higher accuracy than other pertinent modal data such as mode shapes; however only a limited number of frequencies may be measured in the conventional context of natural frequencies. Being able to measure extra frequencies is a key to the success of a frequency-based method. The main part of the thesis is therefore organised around the involvement of the so-called artificial boundary condition (ABC) frequencies to augment the frequency dataset for general structural damage identification. In essence, the ABC frequencies correspond to the natural frequencies of the system with additional pin supports, but may be extracted from specially configured incomplete frequency response function matrix of the original structure without the need of physically imposing the additional supports. In the first part of the research, a particular focus is placed on the actual extraction of these ABC frequencies from physical experiments through effective modal testing, data collection, data processing and analysis. The influences of key processes involved in a typical modal experimental procedure, including high-fidelity measurement of the (impact) excitation input, averaging, windowing, and an effective use of post-processing techniques, particularly the Singular Value Decomposition (SVD) technique, are scrutinised in relation to the extraction of the ABC frequencies. With appropriate implementation of testing and data processing procedures, results demonstrate that all one-pin and two-pin ABC frequencies from the first few modes can be extracted with good quality in a laboratory setting, and the accuracy of extracted ABC frequencies is comparable to natural frequencies of corresponding orders. A comprehensive study is then carried out to investigate the sensitivities of ABC frequencies to damages. Two-pin ABC frequency sensitivity is formulated by extending the expression of anti-resonance sensitivity. On this basis, the mode shape contribution is adopted as a criterion for the selection of more sensitive ABC frequencies to be employed in detailed parameter identification or finite element model updating procedures. The soundness of using ABC frequencies in structural parameter identification and the effectiveness of the above ABC frequency selection method are subsequently examined through case studies involving laboratory experiments and the corresponding FE model updating. Furthermore, a preliminary study is carried out to examine the possibility of formulating ABC frequency-based damage indicator, herein with an analogy to the mode shape curvature, for direct damage assessment. As an extended investigation in the general framework of frequency-based dynamic identification, in the last part of the thesis, a complex dynamic system, namely a railway bridge under moving loads & masses, is evaluated with regard to the various frequency characteristics involved. The variation of the natural frequencies of the bridge-moving mass system, as well as the presence of the apparent frequencies from the trainloads, are analysed in detail. Besides simplified theoretical analysis, a computational model is developed to simulate the combined bridge-moving vehicle/train system, where the vehicle mass is coupled with the bridge via surface contact. The model is verified by comparison with field measurement data and theoretical predictions. Parametric studies enable a clear identification of the correlation of the frequency contents between the response and the trainload, and provide new insight into the significance of the so-called driving and dominant frequencies. It is found that much of the dynamic response phenomena, including the resonance effect, may be explained from the view point of the frequency characteristics of the trainload pattern, which is governed primarily by the ratio between the carriage length and the bridge length. Finally, a resonance severity indicator (the Z-factor) is developed for the assessment of the resonance effect in the railway bridge response when the trainload moves at a resonance speed. Numerical results demonstrate that the proposed methods are effective for the determination of the critical speed and the resonance effects, including the situations where a significant carriage mass is incorporated.

名古屋大学博士学位論文 学位の種類 : 博士(医学)(課程) 学位授与年月日:平成24年3月26日 櫛山泰規氏の博士論文として提出された

Atrial fibrillation and atrial flutter are the most common sustained arrhythmias, however their underlying mechanisms are yet to be fully characterised. This thesis evaluates the electrophysiological and electroanatomical substrate of the atria in patients with these arrhythmias. Experimental studies of atrial fibrillation have demonstrated effective refractory period shortening and conduction slowing as a result of atrial fibrillation giving rise to the concept that "atrial fibrillation begets atrial fibrillation". However, cardioversion to prevent electrical remodelling does not prevent progression of disease, suggesting a "second factor" drives this process. Chapters 2 and 3 evaluate the atrial substrate in patients with "lone" atrial fibrillation. These studies demonstrate such patients, remote from an arrhythmic event, have prolongation of atrial refractoriness, conduction slowing, impairment of sinus node function, site-specific conduction delay, lower voltage and a greater proportion of complex electrograms compared to reference patients. These abnormalities constitute the "second factor" critical to the development and progression of atrial fibrillation. Atrial flutter has a close inter-relationship with atrial fibrillation and these rhythms frequently co-exist. Atrial fibrillation often occurs in patients with heart disease known to demonstrate abnormal atrial substrate; whether similar substrate exists in patients with atrial flutter to account for the co-existence of both arrhythmias is unknown. Chapters 4 and 5 evaluate the atrial substrate in patients with atrial flutter, remote from arrhythmia, demonstrating structural abnormalities characterised by loss of myocardial voltage, conduction slowing and impaired sinus node function, without reduction in atrial refractoriness. These findings implicate a common substrate as the cause of the close inter-relationship between these arrhythmias. There is a frequent association between atrial arrhythmia and sinus node disease for which several mechanisms have been postulated. In addition, there is a size discrepancy between the anatomical sinus node and the much larger functional sinus node complex. little is known about normal sinus node function or the effects of remodelling due to arrhythmia. Chapter 6 characterises sinus node activation to determine the nature and extent of the functional sinus node complex in patients with and without chronic atrial flutter. The functional sinus node complex demonstrates dynamic shifts in activation with preferential pathways of conduction to atrial myocardium. Patients with atrial flutter demonstrate lesser voltage, longer conduction times along preferential pathways and a smaller functional sinus node complex. These findings provide insights into the function of the human sinus node in health and disease. Sites of complex fractionated atrial electrograms and highest dominant frequency are implicated in maintaining atrial fibrillation. Chapter 7 determines the minimum recording duration that accurately characterises electrogram complexity and activation frequency. An electrogram duration of 5 seconds is required to accurately identify these sites. Chapter 8 evaluates the relationship between sites of fractionation and high frequency activation during atrial fibrillation. Greater fractionation and higher dominant frequency are seen in persistent atrial fibrillation and left atria. Preferential areas of high dominant frequency are observed in paroxysmal but not persistent atrial fibrillation. Areas of complex fractionated atrial electrograms are found adjacent to sites of high dominant frequency. / Thesis (Ph.D.) -- University of Adelaide, School of Medicine, 2009

La fibrillation atriale (FA) est l’arythmie soutenue la plus fréquente ; elle entraine une majoration significative de la morbidité et de la mortalité. Les mécanismes qui en sont responsables sont encore incomplètement connus, et sa prise en charge n’est pas optimale. Afin de mieux comprendre la physiopathologie de la FA, nous avons mené différents travaux sur des coeurs de moutons isolés et perfusés par un système de Langendorff mais également en créant un modèle chronique de FA persistante de longue durée. Dans un modèle ovin de FA persistante, nous avons ainsi démontré que la fréquence dominante (DF) de la FA augmentait progressivement pendant les premières semaines de l’arythmie, alors que les épisodes étaient paroxystiques, phénomène en rapport avec le raccourcissement de la durée du potentiel d’action secondaire au remodelage électrophysiologique. La DF se stabilisait dès lors que la FA devenait persistante, une fois le remodelage électrophysiologique maximal. L’accélération de la DF (dDF/dt) était significativement corrélée au temps nécessaire à la transition vers la FA persistante. Le remodelage structurel n’apparaissait que secondairement, une fois l’arythmie devenue persistante. Sur le plan thérapeutique, nous avons étudié les mécanismes anti-arythmiques de la chloroquine (bloqueur d’IK1) et de la ranolazine (bloqueur d’INa), molécules entrainant un ralentissement de la fréquence de rotation des rotors, une diminution de la DF et un retour en rythme sinusal. Ces travaux nous ont permis de mieux appréhender le rôle des ces courants ioniques dans le maintien de la FA. Enfin, nous avons démontré l’efficacité de l’ablation de la FA en utilisant le cryoballon (CB) de deuxième génération, efficacité grevée d’un taux de parésie du nerf phrénique élevé, dont nous avons pu prédire la survenue à l’aide d’un prédicteur simple, la distance entre le bord du CB et la cathéter permettant de stimuler le nerf phrénique pendant l’application. Une meilleure compréhension des mécanismes à l’origine de l’initiation et du maintien de cette arythmie, ainsi qu’une meilleure prise en charge thérapeutique permettraient d’améliorer la qualité de vie des patients et d’en diminuer le taux de complications. / Atrial fibrillation (AF) is the most common sustained arrhythmia, significantly increasing patients’ morbidity and mortality. The mechanisms explaining the initiation and maintenance of the arrhythmia are incompletely understood, and the current treatment strategy is suboptimal. To better understand the pathophysiology of AF, we conducted various projects using Langendorff-perfused sheep hearts and a chronic model of long-standing persistent AF. In the model of persistent AF, we demonstrated that dominant frequency (DF) progressively increases during the first weeks of the arrhythmia, during its paroxysmal stage, due to the electrophysiological remodeling resulting in atrial action potential shortening. DF stabilizes once the electrophysiological remodeling is maximal, and the arrhythmia becomes persitent. The rate of DF increase (dDF/dt) was strongly correlated with the time to persistent AF. Structural remodeling appears secondarily, once transition has occured. We also studied the anti-arrhythmic mechanisms of chloroquine (IK1 blocker) and ranolazine (INa blocker), which slow the frequency of rotation of rotors, decrease the DF and favor reversal to sinus rhythm. These projects helped us to better understand the importance of these currents in AF dynamics. Lastly, we demonstrated the increased efficacy of AF ablation when using the second generation cryoballoon (CB), which regrettably increases the occurrence of phrenic nerve palsy. A simple, reliable predictor of this complication was found, the distance between the lateral edge of the CB and the phrenic nerve stimulating catheter. A better understanding of the mechanisms underlying the initiation and maintenance of AF, in conjunction with better therapeutic strategies will help to improve patients’ quality of life and decrease the complications of the arrhythmia.

This dissertation thesis is focused on the analysis of specific cutting forces and accompanying effects during machining of the new materials, composite materials. The experimental part is split up to two main chapters. In the first chapter, the development of specific cutting forces is analyzed in detail when cutting conditions are changing. The experimental machining of glass/polyester and carbon/epoxy composites is described for fibers orientations 0 a 90 (ie, the orientation of the fibers in the feed rate direction and perpendicular to the feed rate direction). The influence of the cutting tool flank wear on the specific cutting force is investigated further. The last section compares the values of specific cutting forces when machining with carbide milling tools deposited by different types of coating. The second chapter describes the measurement of sound spectrums generated by cutting process, sound maps creating and finding possible correlations between dominant frequencies of the sound and the specific cutting forces, or the cutting tool flank wear. The measurements are described for the cases of machining steel 15 260.7 and glass-polyester composite material.

Atrial fibrillation (AF) is one of the most common cardiac arrhythmias. Nowadays the fibrillatory process is known to be provoked by the high-frequency reentrant activity of certain atrial regions that propagates the fibrillatory activity to the rest of the atrial tissue, and the electrical isolation of these key regions has demonstrated its effectiveness in terminating the fibrillatory process. The location of the dominant regions represents a major challenge in the diagnosis and treatment of this arrhythmia. With the aim to detect and locate the fibrillatory sources prior to surgical procedure, non-invasive methods have been developed such as body surface electrical mapping (BSPM) which allows to record with high spatial resolution the electrical activity on the torso surface or the electrocardiographic imaging (ECGI) which allows to non-invasively reconstruct the electrical activity in the atrial surface. Given the novelty of these systems, both technologies suffer from a lack of scientific knowledge about the physical and technical mechanisms that support their operation. Therefore, the aim of this thesis is to increase that knowledge, as well as studying the effectiveness of these technologies for the localization of dominant regions in patients with AF. First, it has been shown that BSPM systems are able to noninvasively identify atrial rotors by recognizing surface rotors after band-pass filtering. Furthermore, the position of such surface rotors is related to the atrial rotor location, allowing the distinction between left or right atrial rotors. Moreover, it has been found that the surface electrical maps in AF suffer a spatial smoothing effect by the torso conductor volume, so the surface electrical activity can be studied with a relatively small number of electrodes. Specifically, it has been seen that 12 uniformly distributed electrodes are sufficient for the correct identification of atrial dominant frequencies, while at least 32 leads are needed for non-invasive identification of atrial rotors. Secondly, the effect of narrowband filtering on the effectiveness of the location of reentrant patterns was studied. It has been found that this procedure allows isolating the reentrant electrical activity caused by the rotor, increasing the detection rate for both invasive and surface maps. However, the spatial smoothing caused by the regularization of the ECGI added to the temporal filtering causes a large increase in the spurious reentrant activity, making it difficult to detect real reentrant patterns. However, it has been found that maps provided by the ECGI without temporal filtering allow the correct detection of reentrant activity, so narrowband filtering should be applied for intracavitary or surface signal only. Finally, we studied the stability of the markers used to detect dominant regions in ECGI, such as frequency maps or the rotor presence. It has been found that in the presence of alterations in the conditions of the inverse problem, such as electrical or geometrical noise, these markers are significantly more stable than the ECGI signal morphology from which they are extracted. In addition, a new methodology for error reduction in the atrial spatial location based on the curvature of the curve L has been proposed. The results presented in this thesis showed that BSPM and ECGI systems allows to non-invasively locate the presence of high-frequency rotors, responsible for the maintenance of AF. This detection has been proven to be unambiguous and robust, and the physical and technical mechanisms that support this behavior have been studied. These results indicate that both non-invasive systems provide information of great clinical value in the treatment of AF, so their use can be helpful for selecting and planning atrial ablation procedures. / La fibrilación auricular (FA) es una de las arritmias cardiacas más frecuentes. Hoy en día se sabe que el proceso fibrilatorio está provocado por la actividad reentrante a alta frecuencia de ciertas regiones auriculares que propagan la actividad fibrilatoria en el resto del tejido auricular, y se ha demostrado que el aislamiento eléctrico de estas regiones dominantes permite detener el proceso fibrilatorio. La localización de las regiones dominantes supone un gran reto en el diagnóstico y tratamiento de la FA. Con el objetivo de poder localizar las fuentes fibrilatorias con anterioridad al procedimiento quirúrgico, se han desarrollado métodos no invasivos como la cartografía eléctrica de superficie (CES) que registra con gran resolución espacial la actividad eléctrica en la superficie del torso o la electrocardiografía por imagen (ECGI) que permite reconstruir la actividad eléctrica en la superficie auricular. Dada la novedad de estos sistemas, existe una falta de conocimiento científico sobre los mecanismos físicos y técnicos que sustentan su funcionamiento. Por lo tanto, el objetivo de esta tesis es aumentar dicho conocimiento, así como estudiar la eficacia de ambas tecnologías para la localización de regiones dominantes en pacientes con FA. En primer lugar, ha visto que los sistemas CES permiten identificar rotores auriculares mediante el reconocimiento de rotores superficiales tras el filtrado en banda estrecha. Además, la posición de los rotores superficiales está relacionada con la localización de dichos rotores, permitiendo la distinción entre rotores de aurícula derecha o izquierda. Por otra parte, se ha visto que los mapas eléctricos superficiales durante FA sufren una gran suavizado espacial por el efecto del volumen conductor del torso, lo que permite que la actividad eléctrica superficial pueda ser estudiada con un número relativamente reducido de electrodos. Concretamente, se ha visto que 12 electrodos uniformemente distribuidos son suficientes para una correcta identificación de frecuencias dominantes, mientras que son necesarios al menos 32 para una correcta identificación de rotores auriculares. Por otra parte, también se ha estudiado el efecto del filtrado en banda estrecha sobre la eficacia de la localización de patrones reentrantes. Así, se ha visto que este procedimiento permite aislar la actividad eléctrica reentrante provocada por el rotor, aumentando la tasa de detección tanto para señal obtenida de manera invasiva como para los mapas superficiales. No obstante, este filtrado temporal sobre la señal de ECGI provoca un gran aumento de la actividad reentrante espúrea que dificulta la detección de patrones reentrantes reales. Sin embargo, los mapas ECGI sin filtrado temporal permiten la detección correcta de la actividad reentrante, por lo el filtrado debería ser aplicado únicamente para señal intracavitaria o superficial. Por último, se ha estudiado la estabilidad de los marcadores utilizados en ECGI para detectar regiones dominantes, como son los mapas de frecuencia o la presencia de rotores. Se ha visto que en presencia de alteraciones en las condiciones del problema inverso, como ruido eléctrico o geométrico, estos marcadores son significativamente más estables que la morfología de la propia señal ECGI. Además, se ha propuesto una nueva metodología para la reducción del error en la localización espacial de la aurícula basado en la curvatura de la curva L. Los resultados presentados en esta tesis revelan que los sistemas de CES y ECGI permiten localizar de manera no invasiva la presencia de rotores de alta frecuencia. Esta detección es univoca y robusta, y se han estudiado los mecanismos físicos y técnicos que sustentan dicho comportamiento. Estos resultados indican que ambos sistemas no invasivos proporcionan información de gran valor clínico en el tratamiento de la FA, por lo que su uso puede ser de gran ayuda para la selección y planificaci / La fibril·lació auricular (FA) és una de les arítmies cardíaques més freqüents. Hui en dia es sabut que el procés fibrilatori està provocat per l'activitat reentrant de certes regions auriculars que propaguen l'activitat fibril·latoria a la resta del teixit auricular, i s'ha demostrat que l'aïllament elèctric d'aquestes regions dominants permet aturar el procés fibrilatori. La localització de les regions dominants suposa un gran repte en el diagnòstic i tractament d'aquesta arítmia. Amb l'objectiu de poder localitzar fonts fibril·latories amb anterioritat al procediment quirúrgic s'han desenvolupat mètodes no invasius com la cartografia elèctrica de superfície (CES) que registra amb gran resolució espacial l'activitat elèctrica en la superfície del tors o l'electrocardiografia per imatge (ECGI) que permet obtenir de manera no invasiva l'activitat elèctrica en la superfície auricular. Donada la relativa novetat d'aquests sistemes, existeix una manca de coneixement científic sobre els mecanismes físics i tècnics que sustenten el seu funcionament. Per tant, l'objectiu d'aquesta tesi és augmentar aquest coneixement, així com estudiar l'eficàcia d'aquestes tecnologies per a la localització de regions dominants en pacients amb FA. En primer lloc, s'ha vist que els sistemes CES permeten identificar rotors auriculars mitjançant el reconeixement de rotors superficials després del filtrat en banda estreta. A més, la posició dels rotors superficials està relacionada amb la localització d'aquests rotors, permetent la distinció entre rotors de aurícula dreta o esquerra. També s'ha vist que els mapes elèctrics superficials durant FA pateixen un gran suavitzat espacial per l'efecte del volum conductor del tors, el que permet que l'activitat elèctrica superficial pugui ser estudiada amb un nombre relativament reduït d'elèctrodes. Concretament, s'ha vist que 12 elèctrodes uniformement distribuïts són suficients per a una correcta identificació de freqüències dominants auriculars, mentre que són necessaris almenys 32 per a una correcta identificació de rotors auriculars. D'altra banda, també s'ha estudiat l'efecte del filtrat en banda estreta sobre l'eficàcia de la localització de patrons reentrants. Així, s'ha vist que aquest procediment permet aïllar l'activitat elèctrica reentrant provocada pel rotor, augmentant la taxa de detecció tant pel senyal obtingut de manera invasiva com per als mapes superficials. No obstant això, aquest filtrat temporal sobre el senyal de ECGI provoca un gran augment de l'activitat reentrant espúria que dificulta la detecció de patrons reentrants reals. A més, els mapes proporcionats per la ECGI sense filtrat temporal permeten la detecció correcta de l'activitat reentrant, per la qual cosa el filtrat hauria de ser aplicat únicament per a senyal intracavitària o superficial. Per últim, s'ha estudiat l'estabilitat dels marcadors utilitzats en ECGI per a detectar regions auriculars dominants, com són els mapes de freqüència o la presència de rotors. S'ha vist que en presència d'alteracions en les condicions del problema invers, com soroll elèctric o geomètric, aquests marcadors són significativament més estables que la morfologia del mateix senyal ECGI. A més, s'ha proposat una nova metodologia per a la reducció de l'error en la localització espacial de l'aurícula basat en la curvatura de la corba L. Els resultats presentats en aquesta tesi revelen que els sistemes de CES i ECGI permeten localitzar de manera no invasiva la presència de rotors d'alta freqüència. Aquesta detecció és unívoca i robusta, i s'han estudiat els mecanismes físics i tècnics que sustenten aquest comportament. Aquests resultats indiquen que els dos sistemes no invasius proporcionen informació de gran valor clínic en el tractament de la FA, pel que el seu ús pot ser de gran ajuda per a la selecció i planificació de procediments d'ablació auricular. / Rodrigo Bort, M. (2016). Non-invasive identification of atrial fibrillation drivers [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/75346 / TESIS / Premios Extraordinarios de tesis doctorales

No description available.

Many families of catfish produce sounds via pectoral spine stridulation and/or swim bladder compression using sonic muscles attached to the swim bladder. The sound production capabilities and characteristics in Loricariidae, the largest catfish family, have not been well examined. Sounds produced by two loricariid catfish species, Macrotocinclus affinis and Pterygoplichthys gibbiceps were recorded. Both species produce broad band calls via pectoral spine stridulation. These species produce sounds by rubbing the ridges of the dorsal process of the pectoral spine base against the groove of the pectoral girdle. Call duration was generally shorter in M. affinis (2-15 ms) as opposed to those produced by P. gibbiceps (20-200 ms). Mean dominant frequencies were approximately 4000 Hz for M. affinis and 1000 (abduction) and 4500 Hz (adduction) for P. gibbiceps. Light and scanning electron microscopy were used to examine the dorsal process of the pectoral spines from the largest and smallest M. affinis, and from a wide range of sizes from P. gibbiceps. Mean distances between dorsal process ridges of M. affinis and P. gibbicepswere approximately 50 and 160 microns, respectively. For P. gibbiceps, dominant frequency was an inverse function of total length and inter-ridge distance.

The angular location of an acoustic source can be estimated by measuring an acoustic direction of incidence based solely on the noise produced by the source. Methods for determining the direction of incidence based on sound intensity, the phase of cross-spectral functions, and cross-correlation functions are available. In this current work, we implement Dominant Frequency SElection (DFSE) algorithm. Direction of arrival (DOA) estimation usingmicrophone arrays is to use the phase information present in signals from microphones that are spatially separated. DFSE uses the phase difference between the Fourier transformedsignals to estimate the direction ofarrival (DOA)and is implemented using a three-element ’L’ shaped microphone array, linear microphone array, and planar 16-microphone array. This method is based on simply locating the maximum amplitude from each of the Fourier transformed signals and thereby deriving the source location by solving the set of non-linear least squares equations. For any pair of microphones, the surface on whichthe time difference ofarrival (TDOA) is constant is a hyperboloidoftwo sheets. Acoustic source localization algorithms typically exploit this fact by grouping all microphones into pairs, estimating the TDOA of each pair, then finding the point where all associated hyperboloids most nearly intersect. We make use of both closed-form solutions and iterative techniques to solve for the source location.Acoustic source positioned in 2-dimensional plane and 3-dimensional space have been successfully located.