Yes / There is increasing concern with protecting quiet and tranquil areas from intrusive noise. Noise reduction at source and barriers to transmission are mitigation measures often considered. An alternative is to attempt to mask or distract attention away from the noise source. The masking or distracting sound source should be pleasant so that it does not add to any irritation caused by the noise source alone. The laboratory measurements described in this paper consisted of capturing under controlled conditions the third octave band spectra of water falling onto water, gravel, bricks and small boulders and various combinations. These spectra were then matched with typical traffic noise spectra to assess the degree of masking that could be expected for each option. Recordings were also taken during each measurement and these were used later to enable the subjective assessment of the tranquility of the sounds. It was found that there were differences between water sounds both in terms of masking and their subjective impact on tranquility.

2. A modified model of heart-arterial system was proposed for describing the timing of the second heart sound as a result of the heart-arterial interaction. Simulation results suggest that RS2 bears a significant negative correlation with both SBP and DBP as heart rate, cardiac contractility and peripheral resistance varies. The hypothesis was supported by the experimental data. To our knowledge, it is the first study describing the relation of the timing of S2 to BP by both the model-based study and experimental data. / 3. As a preliminary study, a linear predication model using RS2 with a novel calibration scheme was proposed for BP estimation and it has been evaluated in clinical test on 85 volunteers including 18 hypertensives. The results indicate that the approach has the potential to achieve the accuracy required for medical diagnosis. / Cuffless BP measurement has been proposed as a new concept in recent years to realize the continuous monitoring of BP. This research focuses on the investigation of cuffless BP monitoring technique using heart sound information. Specifically, the thesis proposes a new cuffless technique based on the timing of the second heart sound (S2), which will enable a novel wearable design of BP monitor, for instance, a multifunctional electronic stethoscope. / Finally, based on the findings on both theoretical and experimental studies, a linear prediction model with a novel calibration scheme has been proposed to estimate the BP using 1/RS2. The proposed method was evaluated in a clinical test on 85 volunteers aged 40+/-13 years, including 18 hypertensives. The average of BP measured by simultaneous ausculatory and oscillometric approaches was used as a reference. The results of clinical test shows that the RS2 based approach can estimate SBP and DBP within the 2.1+/-7.4 mmHg and 0.8+/-6.6 mmHg of the reference respectively, indicating the approach has the potential to achieve the accuracy required for medical diagnosis according to AAMI standard (mean error within +/-5mmHg and SD less than 8mmHg) and BHS protocol. / First, a mathematical model has been developed to investigate the effects of aortic BP on the aortic component (A2) in S2 produced by the vibration of the closed aortic valve. The nonlinear elasticity of aortic wall has been introduced to the model, reflecting the nature of aortic wall tissue and extending the model to the applications involving wide BP variations. The results of simulation show that the fundamental frequency and amplitude of A2 increases as aortic systolic blood pressure (SBP) is elevated, which is able to explain the 'accentuated S2' usually heard in the hypertensives. Nevertheless, the possibility of BP measurement using spectral information of externally recorded heart sounds still needs a careful examination because the frequency characteristics tends to be blurred during sound transmission. / Hypertension, known as 'a silent killer', is an important public health challenge, afflicting approximately 1 billion adults around the world. The monitoring of blood pressure (BP) is vitally important in order to identify hypertension and treat it earlier before serious health problems are developed. The conventional BP measurement provides only intermittent BP and causes circulatory interference if the cuff is inflated frequently. There is an urgent need to develop new devices which are fully wearable and unobtrusive for noninvasive and continuous monitoring of arterial BP in daily life. / Second, a modified model of heart-arterial system has been proposed in this thesis for describing the timing of aortic valve closure as a result of heart-arterial interaction. A timing parameter, RS2, was defined as the time delay from the peak of ECG R wave to the onset of S2. The study has investigated the relation between RS2 and aortic BP under varying peripheral resistance, arterial compliance, heart rate, cardiac contractility and preload. Based on the simulation results of parametric analysis, it is hypothesized that RS2 bears a significant negative correlation with both SBP and diastolic blood pressure (DBP) as the peripheral resistance, heart rate or cardiac contractility varies. / Third, in order to verify the findings of the model-based study, three experiments were carried out to explore the relationship between RS2 and BP. The alterations of RS2 in the dynamic-exercise experiments are mainly attributable to the interactive effect of the changes in heart rate, cardiac contractility and peripheral resistance, and the effect of heart rate is dominant. In two dynamic-exercise experiments, the timing parameter, RS2, exhibited a close inverse correlation with SBP (r =0.892 and r =0.845, p<0.05 in both experiments) and a moderate inverse correlation with diastolic blood pressure (DBP) (r = 0.687, p<0.05 and r =0.660, p>0.05). The correlations are comparable to those of PTT-based parameters. However, due to the restricted range of the BP variation, there was no significant correlation observed in long-term rest monitoring experiment. Moreover, the standard deviation (SD) of the errors for SBP and DBP estimated by linear fitting of 1/RS2 is close to that of PTT-based estimation. The results also suggest that the ability of RS2 on BP estimation is as good as that of the PTT based parameters. / To summarize, the original contributions of the thesis are: 1. By the introduction of the nonlinear elasticity of aortic wall, a mathematical model for the vibration of the closed aortic valve was improved and extended to the applications involving wide variations of BP To my knowledge, this represents the first study to look into the effects of aortic BP on the frequency characteristic of S2 from the theoretical point of view. / Zhang Xin-Yu. / "September 2006." / Adviser: Yuan-Ting Zhang. / Source: Dissertation Abstracts International, Volume: 68-09, Section: B, page: 6125. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Yip Lung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Abstracts in English and Chinese. / Chapter 1 --- Introduction / Chapter 1.1 --- Heart and Lung Diseases --- p.1 / Chapter 1.1.1 --- Hong Kong --- p.1 / Chapter 1.1.2 --- China --- p.2 / Chapter 1.1.3 --- the United States of America (USA) --- p.3 / Chapter 1.2 --- Auscultation --- p.3 / Chapter 1.2.1 --- Introduction of Auscultation --- p.4 / Chapter 1.2.2 --- Comparison between Auscultation and Ultrasound --- p.6 / Chapter 1.3 --- Stethoscope --- p.7 / Chapter 1.3.1 --- History of Stethoscope --- p.7 / Chapter 1.3.2 --- New Electronic Stethoscope --- p.14 / Chapter 1.4 --- Main Purpose of the Study --- p.16 / Chapter 1.5 --- Organization of Thesis --- p.16 / References --- p.18 / Chapter 2 --- A New Electronic Stethoscope's Head / Chapter 2.1 --- Introduction --- p.20 / Chapter 2.2 --- Biopotential Electrode --- p.21 / Chapter 2.2.1 --- Flexible Electrode --- p.21 / Chapter 2.2.2 --- Laplacian Electrocardiogram --- p.22 / Chapter 2.3 --- Transducer --- p.25 / Chapter 2.4 --- Design of the Head of Stethoscope --- p.26 / Chapter 2.5 --- Experimental Results --- p.27 / Chapter 2.5.1 --- Bias Voltage of Condenser Microphone --- p.27 / Chapter 2.5.2 --- Frequency Response of New Stethoscope's Head --- p.29 / Chapter 2.6 --- Discussion --- p.30 / Chapter 2.7 --- Section Summary --- p.31 / References --- p.33 / Chapter 3 --- Signal Pre-processing Unit / Chapter 3.1 --- Introduction --- p.35 / Chapter 3.2 --- High Input Impedance IC Amplifier --- p.36 / Chapter 3.3 --- Voltage Control Voltage Source High Pass Filter Circuit --- p.37 / Chapter 3.4 --- Multiple Feed Back Low Pass Filter Circuit --- p.39 / Chapter 3.5 --- Overall Circuit --- p.41 / Chapter 3.6 --- Experimental Results --- p.43 / Chapter 3.7 --- Discussion --- p.46 / Chapter 3.8 --- Section Summary --- p.47 / References --- p.48 / Chapter 4 --- Central Platform / Chapter 4.1 --- Introduction --- p.49 / Chapter 4.2 --- Adaptive Filter --- p.49 / Chapter 4.2.1 --- Introduction to Adaptive Filtering --- p.49 / Chapter 4.2.2 --- Least-Mean-Square (LMS) Algorithm --- p.51 / Chapter 4.2.3 --- Applications --- p.52 / Chapter 4.3 --- Offline Processing --- p.54 / Chapter 4.3.1 --- WINDAQ and MATLAB --- p.55 / Chapter 4.3.2 --- Direct Reference Algorithm --- p.57 / Chapter 4.3.3 --- Determination of Parameters in DRA --- p.62 / Chapter 4.3.4 --- Experimental Results of DRA --- p.67 / Chapter 4.3.5 --- Acoustic Waveform Based Algorithm --- p.72 / Chapter 4.3.6 --- Experimental Results of AWBA --- p.81 / Chapter 4.4 --- Online Processing --- p.85 / Chapter 4.4.1 --- LABVIEW --- p.85 / Chapter 4.4.2 --- Automated Gain Control --- p.88 / Chapter 4.4.3 --- Implementation of LMS adaptive filter --- p.89 / Chapter 4.4.4 --- Experimental Results of Online-AGC --- p.92 / Chapter 4.5 --- Discussion --- p.93 / Chapter 4.6 --- Section Summary --- p.97 / References --- p.98 / Chapter 5 --- Conclusion and Further Development / Chapter 5.1 --- Conclusion of the Main Contribution --- p.100 / Chapter 5.2 --- Future Works --- p.102 / Chapter 5.2.1 --- Modification of the Head of Stethoscope --- p.102 / Chapter 5.2.2 --- Validation of Abnormal Breath --- p.102 / Chapter 5.2.3 --- Low Frequency Analysis --- p.102 / Chapter 5.2.4 --- AGC-AWBA Approach --- p.102 / Chapter 5.2.5 --- Standalone Device --- p.103 / Chapter 5.2.6 --- Demand on Stethoscope --- p.109 / References --- p.110 / Appendix / Chapter A.1 --- Determination of parameters in VCVS High Pass Filter --- p.106 / Chapter A.2 --- Determination of parameters in MFB Low Pass Filter --- p.110 / Chapter A.3 --- Source code of DRA (MATLAB) --- p.114 / Chapter A.4 --- Source code of AWBA (MATLAB) --- p.129 / Chapter A.5 --- Source code of online AGC (LABVIEW) --- p.134

More than one million fetal deaths occur in the United States every year [1]. Monitoring the long-term heart rate variability provides a great amount of information about the fetal health condition which requires continuous monitoring of the fetal heart rate. All the existing technologies have either complex instrumentation or need a trained professional at all times or both. The existing technologies are proven to be impractical for continuous monitoring [2]. Hence, there is an increased interest towards noninvasive, continuous monitoring, and less expensive technologies like fetal phonocardiography. Fetal Phonocardiography (FPCG) signal is obtained by placing an acoustic transducer on the abdomen of the mother. FPCG is rich in physiological bio-signals and can continuously monitor the fetal heart rate non-invasively. Despite its high diagnostic potential, it is still not being used as the secondary point of care. There are two challenges as to why it is still being considered as the secondary point of care; in the data acquisition system and the signal processing methodologies. The challenges pertaining to data acquisition systems are but not limited to sensor placement, maternal obesity and multiple heart rates. While, the challenges in the signal processing methodologies are dynamic nature of FPCG signal, multiple known and unknown signal components and SNR of the signal. Hence, to improve the FPCG based care, challenges in FPCG signal processing methodologies have been addressed in this study. A comparative evaluation was presented on various advanced signal processing techniques to extract the bio-signals with fidelity. Advanced signal processing approaches, namely empirical mode decomposition, spectral subtraction, wavelet decomposition and adaptive filtering were used to extract the vital bio-signals. However, extracting these bio-signals with fidelity is a challenging task in the context of FPCG as all the bio signals and the unwanted artifacts overlap in both time and frequency. Additionally, the signal is corrupted by noise induced from the fetal and maternal movements as well the background and the sensor. Empirical mode decomposition algorithm was efficient to denoise and extract the maternal and fetal heart sounds in a single step. Whereas, spectral subtraction was used to denoise the signal which was later subjected to wavelet decomposition to extract the signal of interest. On the other hand, adaptive filtering was used to estimate the fetal heart sound from a noisy FPCG where maternal heart sound was the reference input. The extracted signals were validated by obtaining the frequency ranges computed by the Short Time Fourier Transform (STFT). It was observed that the bandwidths of extracted fetal heart sounds and maternal heart sounds were consistent with the existing gold standards. Furthermore, as a means of additional validation, the heart rates were calculated. Finally, the results obtained from all these methods were compared and contrasted qualitatively and quantitatively.

Un des grands enjeux actuels dans le domaine de la synthèse sonore consiste à proposer des stratégies de contrôle intuitif accessible à un grand nombre d'utilisateurs. Parmi les attributs fondamentaux du son, ceux qui sont liés au mouvement restent encore largement inexplorés et, de fait, difficilement contrôlables. Cette thèse s'intéresse à la perception des caractéristiques des sons monophoniques qui varient au cours du temps et qui sont à l'origine de la notion perceptive de ''mouvement évoqué'', ainsi qu'à la mise au point d'une stratégie de contrôle intuitif. Pour cela, nous avons mis au point une série d'expériences basées sur des protocoles de catégorisation et d'évaluation sonore par le biais de dessins via une interface graphique paramétrée. Afin de favoriser l'écoute sur les attributs intrinsèques du son, nous avons privilégié l'utilisation de sons dits ''abstraits" pour lesquels la source physique n'est pas facilement identifiable. Les résultats de ces expériences nous ont permis de définir un ensemble de dimensions perceptives importantes pour la caractérisation du mouvement évoqué, telles que la forme de la trajectoire, l'orientation ou bien la taille. Ces dimensions ont été par la suite validées grâce à un protocole expérimental exploitant la synthèse sonore. Le travail réalisé ouvre de nombreuses perspectives, notamment dans les domaines de la réalité virtuelle, du ''design sonore'' et de la musique. La méthodologie proposée vise à être suffisamment générale pour être transposable à l'étude d'autres attributs perceptifs liés au ressenti (émotions, qualité ...). / An important issue within sound synthesis, is to propose intuitive control strategies that are accessible to most potential users. Among fundamental sound attributes, the ones linked to motion are almost unexplored and thus cannot be easily controlled. This Ph.D. concerns the perception of time varying characteristics of monophonic sounds, which leads to the notion of motion evoked by sounds and the conception of intuitive control strategies for such motions. To address those questions, we developed several experiments based on categorization tasks and evaluations through drawings using a parameterized graphical interface. In order to help listeners focus on intrinsic sound attributes, we mainly used so-called ''abstract'' sounds for which the physical sound source is not easily recognizable. The results of those experiments enabled us to identify attributes that characterize evoked motion from a perceptual point of view, such as shape, direction and size of the trajectory. Those dimensions were further validated in an experimental protocol using sound synthesis. This work opens many perspectives, in particular within virtual reality, sound design and musical domains. The proposed methodology aimed at being sufficiently generic to be transposed to other perceptual attributes such as emotions and quality.

Wong Chun Yin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 137-143). / Abstracts in English and Chinese. / LIST OF FIGURES --- p.xi / LIST OF TABLES --- p.xv / LIST OF ACRONYMS --- p.xvi / Chapter CHAPTER ONE - --- INTRODUCTION / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Research background --- p.1 / Chapter 1.2.1 --- Urban park functions and challenges --- p.1 / Chapter 1.2.2 --- Urban park acoustic environment --- p.2 / Chapter 1.3 --- Urban Parks in Hong Kong --- p.5 / Chapter 1.4 --- Conceptual framework and research objectives --- p.7 / Chapter 1.5 --- Research significance --- p.9 / Chapter CHAPTER TWO - --- LITERATURE REVIEW / Chapter 2.1 --- Introduction --- p.11 / Chapter 2.2 --- Changing approach in managing noise problem in living environment: from noise control to soundscape planning --- p.12 / Chapter 2.2.1 --- Noise control: sound (noise) as a waste to avoid --- p.12 / Chapter 2.2.2 --- Soundscape planning: sound as a resource to utilize --- p.12 / Chapter 2.2.3 --- Soundscape as a guiding principle --- p.13 / Chapter 2.2.4 --- The importance of soundscape --- p.14 / Chapter 2.2.5 --- Criteria for soundscape planning --- p.15 / Chapter 2.2.5.1 --- Sound intensity and quietness --- p.15 / Chapter 2.2.5.2 --- "Sound source, soundscape clarity and sound preference" --- p.16 / Chapter 2.2.5.3 --- "Sound information content, sound-image congruence and acoustic masking" --- p.18 / Chapter 2.2.5.4 --- Acoustic comfort --- p.20 / Chapter 2.2.5.5 --- Acoustic objectives --- p.20 / Chapter 2.2.6 --- From soundscape planning to environmental design --- p.21 / Chapter 2.3 --- Impact of road traffic noise on human --- p.21 / Chapter 2.3.1 --- Detection of road traffic noise --- p.22 / Chapter 2.3.2 --- Response to road traffic noise --- p.22 / Chapter 2.3.2.1 --- Reaction to noise --- p.23 / Chapter 2.3.2.2 --- Physiological response --- p.24 / Chapter 2.3.2.3 --- Behavioural response --- p.24 / Chapter 2.3.2.4 --- Cognitive response --- p.25 / Chapter 2.3.3 --- Moderating factors for road traffic noise impact --- p.25 / Chapter 2.3.3.1 --- Auditory masking --- p.25 / Chapter 2.3.3.2 --- Visual screening --- p.26 / Chapter 2.4 --- Previous studies on urban park soundscape --- p.27 / Chapter 2.4.1 --- Focus on sound intensity --- p.27 / Chapter 2.4.2 --- Sound as a resource to utilize --- p.28 / Chapter 2.4.3 --- Recommendations on park design --- p.29 / Chapter 2.4.4 --- Research gaps --- p.31 / Chapter CHAPTER THREE - --- METHODOLOGY / Chapter 3.1 --- Introduction --- p.33 / Chapter 3.2 --- Site selection --- p.33 / Chapter 3.3 --- Characterizing urban park soundscape --- p.38 / Chapter 3.3.1 --- Identification of sound source --- p.38 / Chapter 3.3.2 --- Field Measurement of Sound intensity and frequency spectrum --- p.40 / Chapter 3.3.3 --- Contribution from road traffic noise --- p.41 / Chapter 3.3.4 --- Questionnaire design to study human perception --- p.43 / Chapter 3.3.5 --- Sampling strategy --- p.47 / Chapter 3.4 --- Summary --- p.48 / Chapter CHAPTER FOUR - --- SOUNDSCAPE OF URBAN PARKS IN HONG KONG / Chapter 4.1 --- Introduction --- p.50 / Chapter 4.2 --- Sound source --- p.50 / Chapter 4.2.1 --- Mechanical sounds --- p.57 / Chapter 4.2.2 --- Natural sounds --- p.57 / Chapter 4.2.3 --- Man-made sounds --- p.59 / Chapter 4.2.4 --- Soundscape clarity --- p.59 / Chapter 4.3 --- Sound Intensity --- p.63 / Chapter 4.4 --- Contribution from road traffic noise to urban park sound intensity --- p.66 / Chapter 4.5 --- Frequency spectrum --- p.73 / Chapter 4.6 --- Effect of topographic variations --- p.76 / Chapter 4.7 --- Conclusion --- p.82 / Chapter CHAPTER FIVE - --- PARK VISITOR'S PERCEPTION ON URBAN PARK SOUNDSCAPE / Chapter 5.1 --- Introduction --- p.84 / Chapter 5.2 --- Urban park noisiness --- p.84 / Chapter 5.3 --- Sound source --- p.85 / Chapter 5.4 --- Sound preference --- p.87 / Chapter 5.5 --- Effect of park size --- p.93 / Chapter 5.6 --- Effect of park function --- p.94 / Chapter 5.7 --- Effect of fountain --- p.95 / Chapter 5.8 --- Perceived importance of tranquility --- p.96 / Chapter 5.9 --- Conclusion --- p.101 / Chapter CHAPTER SIX - --- IMPLICATIONS OF RESEARCH FINDINGS ON URBAN PARK SOUNDSCAPE DESIGN / Chapter 6.1 --- Introduction --- p.102 / Chapter 6.2 --- Soundscape of urban parks in Hong Kong: undesirable yet being adapted… --- p.102 / Chapter 6.3 --- Enhancing soundscape identity of urban parks --- p.103 / Chapter 6.4 --- Small parks --- p.104 / Chapter 6.5 --- Large parks --- p.107 / Chapter 6.6 --- Conclusion --- p.109 / Chapter CHAPTER SEVEN - --- CONCLUSION / Chapter 7.1 --- Introduction --- p.110 / Chapter 7.2 --- Summary of findings --- p.110 / Chapter 7.3 --- Limitations of the research --- p.115 / Chapter 7.3.1 --- Park visitor's aspiration for desirable soundscape --- p.115 / Chapter 7.4 --- Further studies for designing a desirable urban park soundscape --- p.116 / APPENDIX ONE --- p.118 / APPENDIX TWO --- p.122 / REFERENCES --- p.137

In conservation ecology, abundance estimates are an important factor from which management decisions are based. Methods to estimate abundance of cetaceans from visual detections are largely developed, whereas parallel methods based on passive acoustic detections are still in their infancy. To estimate the abundance of cetacean species using acoustic detection data, it is first necessary to correctly identify the species that are detected. The current automatic PAMGUARD Whistle Classifier used to automatically identify whistle detection of cetacean species is modified with the objective to facilitate the use of these detections to estimate cetacean abundance. Given the variability of cetacean sounds within and between species, developing an automated species classifier with a 100% correct classification probability for any species is unfeasible. However, through the examples of two case studies it is shown that large and high quality datasets with which to develop these automatic classifiers increase the probability of creating reliable classifiers with low and precise misclassification probability. Given that misclassification is unavoidable, it is necessary to consider the effect of misclassified detections on the number of observed acoustic calls detected and thus on abundance estimates, and to develop robust methods to cope with these misclassifications. Through both heuristic and Bayesian approaches it is demonstrated that if misclassification probabilities are known or estimated precisely, it is possible to estimate the true number of detected calls accurately and precisely. However, misclassification and uncertainty increase the variance of the estimates. If the true numbers of detections from different species are similar, then a small amount of misclassification between species and a small amount of uncertainty in the probabilities of misclassification does not have a detrimental effect on the overall variance and bias of the estimate. However, if there is a difference in the encounter rate between species calls associated with a large amount of uncertainty in the probabilities of misclassification, then the variance of the estimates becomes larger and the bias increases; this in return increases the variance and the bias of the final abundance estimate. This study despite not bringing perfect results highlights for the first time the importance of dealing with the problem of species misclassification for cetacean if acoustic detections are to be used to estimate abundance of cetaceans.

Tracheal respiratory sounds analysis has been investigated as a non-invasive method to estimate respiratory flow and upper airway obstruction. However, the flow-sound relationship is highly variable among subjects which makes it challenging to estimate flow in general applications. Therefore, a robust model for acoustical flow estimation in a large group of individuals did not exist before. On the other hand, a major application of acoustical flow estimation is to detect flow limitations in patients with obstructive sleep apnea (OSA) during sleep. However, previously the flow--sound relationship was only investigated during wakefulness among healthy individuals. Therefore, it was necessary to examine the flow-sound relationship during sleep in OSA patients. This thesis takes the above challenges and offers innovative solutions. First, a modified linear flow-sound model was proposed to estimate respiratory flow from tracheal sounds. To remove the individual based calibration process, the statistical correlation between the model parameters and anthropometric features of 93 healthy volunteers was investigated. The results show that gender, height and smoking are the most significant factors that affect the model parameters. Hence, a general acoustical flow estimation model was proposed for people with similar height and gender. Second, flow-sound relationship during sleep and wakefulness was studied among 13 OSA patients. The results show that during sleep and wakefulness, flow-sound relationship follows a power law, but with different parameters. Therefore, for acoustical flow estimation during sleep, the model parameters should be extracted from sleep data to have small errors. The results confirm reliability of the acoustical flow estimation for investigating flow variations during both sleep and wakefulness. Finally, a new method for sleep apnea detection and monitoring was developed, which only requires recording the tracheal sounds and the blood's oxygen saturation level (SaO2) data. It automatically classifies the sound segments into breath, snore and noise. A weighted average of features extracted from sound segments and SaO2 signal was used to detect apnea and hypopnea events. The performance of the proposed approach was evaluated on the data of 66 patients. The results show high correlation (0.96,p < 0.0001) between the outcomes of our system and those of the polysomnography. Also, sensitivity and specificity of the proposed method in differentiating simple snorers from OSA patients were found to be more than 91%. These results are superior or comparable with the existing commercialized sleep apnea portable monitors.

Tracheal respiratory sounds analysis has been investigated as a non-invasive method to estimate respiratory flow and upper airway obstruction. However, the flow-sound relationship is highly variable among subjects which makes it challenging to estimate flow in general applications. Therefore, a robust model for acoustical flow estimation in a large group of individuals did not exist before. On the other hand, a major application of acoustical flow estimation is to detect flow limitations in patients with obstructive sleep apnea (OSA) during sleep. However, previously the flow--sound relationship was only investigated during wakefulness among healthy individuals. Therefore, it was necessary to examine the flow-sound relationship during sleep in OSA patients. This thesis takes the above challenges and offers innovative solutions. First, a modified linear flow-sound model was proposed to estimate respiratory flow from tracheal sounds. To remove the individual based calibration process, the statistical correlation between the model parameters and anthropometric features of 93 healthy volunteers was investigated. The results show that gender, height and smoking are the most significant factors that affect the model parameters. Hence, a general acoustical flow estimation model was proposed for people with similar height and gender. Second, flow-sound relationship during sleep and wakefulness was studied among 13 OSA patients. The results show that during sleep and wakefulness, flow-sound relationship follows a power law, but with different parameters. Therefore, for acoustical flow estimation during sleep, the model parameters should be extracted from sleep data to have small errors. The results confirm reliability of the acoustical flow estimation for investigating flow variations during both sleep and wakefulness. Finally, a new method for sleep apnea detection and monitoring was developed, which only requires recording the tracheal sounds and the blood's oxygen saturation level (SaO2) data. It automatically classifies the sound segments into breath, snore and noise. A weighted average of features extracted from sound segments and SaO2 signal was used to detect apnea and hypopnea events. The performance of the proposed approach was evaluated on the data of 66 patients. The results show high correlation (0.96,p < 0.0001) between the outcomes of our system and those of the polysomnography. Also, sensitivity and specificity of the proposed method in differentiating simple snorers from OSA patients were found to be more than 91%. These results are superior or comparable with the existing commercialized sleep apnea portable monitors.

Diss. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 5 uppsatser.