Detection of squawks in respiratory sounds of mechanically ventilated COVID-19 patients

Mechanically ventilated patients typically exhibit abnormal respiratory sounds. Squawks are short inspiratory adventitious sounds that may occur in patients with pneumonia, such as COVID-19 patients. In this work we devised a method for squawk detection in mechanically ventilated patients by developing algorithms for respiratory cycle estimation, squawk candidate identification, feature extraction, and clustering. The best classifier reached an F1 of 0.48 at the sound file level and an F1 of 0.66 at the recording session level. These preliminary results are promising, as they were obtained in noisy environments. This method will give health professionals a new feature to assess the potential deterioration of critically ill patients.publishe

Lung Sounds Classification Based on Time Domain Features

Signal complexity in lung sounds is assumed to be able to differentiate and classify characteristic lung sound between normal and abnormal in most cases. Previous research has employed a variety of modification approaches to obtain lung sound features. In contrast to earlier research, time-domain features were used to extract features in lung sound classification. Electromyogram (EMG) signal analysis frequently employs this time-domain characteristic. Time-domain features are MAV, SSI, Var, RMS, LOG, WL, AAC, DASDV, and AFB. The benefit of this method is that it allows for direct feature extraction without the requirement for transformation. Several classifiers were used to examine five different types of lung sound data. The highest accuracy was 93.9 percent, obtained Using the decision tree with 9 types of time-domain features. The proposed method could extract features from lung sounds as an alternative

Hjorth Descriptor Measurement on Multidistance Signal Level Difference for Lung Sound Classification

Biological signals have a multiscale nature; hence, many multiscale methods for biological signal analysis have been developed. One of the most popular multiscale methods is the coarse-grained procedure. The coarse-grained procedure has some drawbacks, such as a decreased variance of the signal, since the coarse-grained procedure eliminates the fast temporal scale. As such, other multiscale methods were developed to overcome the limitation of the coarse-grained procedure. In this study, we proposed a new multiscale method that preserves variance of the signal. In our proposed method, we split the signal into a new sequencing signal by using the multi-distance signal level difference (MSLD) method. In MSLD, a set of new signals emerged from the absolute value of two data samples' difference at a defined distance. To evaluate the MSLD performance, we used Hjorth descriptor as the feature extraction method in the output signal. The results were classified using multilayer perceptron (MLP). The proposed method was tested on five classes of lung sound data. The results showed that the proposed method achieved the maximum accuracy of 98.76% for the 81 data. The resulting accuracy was higher than the multiscale Hjorth descriptor using the coarse-grained procedure in our previous research. The MSLD could be combined with feature extraction methods other than Hjorth descriptor for future studie

Identificação de estertores em sons respiratórios utilizando transformada wavelet e análise de discriminante linear

Crackles are adventitious and discontinuous breath sounds that occur in lung diseases. Time domain parameters classify the crackles as fine, medium, and coarse, and may have positive or negative polarity. This work investigates methods and tools to characterize and classify crackles. Samples of breath sounds containing crackles were normalized and resampled at 8 kHz. Several experiments using the discrete wavelet transform (DWT), linear discriminant analysis (LDA), and k-NN have been performed, and evaluated with ROC analysis. A pattern recognition system was implemented with DWT, LDA and k-NN to classify fine and coarse crackles, and normal breath sounds. The experiment with different signal border extension methods during DWT decomposition showed the influence on the results of the characterization. The results indicate that the methods ZPD, SP0, SYMH, SYMW, ASYMH, PPD and PER are recommended, while SP1 and ASYMW methods are not recommended for the decomposition and characterization of crackles because they generate different characteristics in the higher subbands. Another experiment showed that the characterization of crackles using DWT can be made using certain decomposition subbands (D3, D4, and D5 with signal sampled at 8 kHz), thus reducing the computational effort. Another classification system implemented using LDA and DWT showed that crackles can be classified by their polarity indicating a high degree of accuracy (AUC rate up to 0.9943 for Symlet 19). Two experiments were conducted for mother-wavelet selection that best characterizes crackles. The first one quantitatively evaluated the similarity between the crackle and several mother-wavelets using Pearson's correlation coefficient. The mother-wavelet that resulted a strong correlation with the crackles, being most indicated for use were: Reverse Biorthogonal 3.7, 5.5 Biorthogonal Reverse, Reverse Biorthogonal 3.5, Daubechies 5, Symlet 5, Daubechies 6, 7, and Symlet Daubechies 7. The second experiment selected mother-wavelets by the power concentration in subbands. Previous trials already shown that the energy of the crackles decomposed by DWT are concentrated in a few subbands, so mothers-wavelet that concentrate larger percentage of the energy in a specific subband were selected, which were Daubechies 7, Symlet 7, Coiflet 3 and Symlet 12. The final experiment performed was a combination of mother-wavelets to improve the separability of crackles and normal breath sounds. The experiment showed that a classification system using DWT, LDA, and a linear classifier may totally separate the two classes (AUC ratio = 1) when the combination of mother-wavelets to generate the feature vector of the signals is used.CAPESEstertores são sons respiratórios adventícios e descontínuos que ocorrem em patologias pulmonares. Parâmetros no domínio do tempo classificam os estertores como finos, médios e grossos, e podem ter polaridade positiva ou negativa. Este trabalho investiga métodos e ferramentas para caracterizar e classificar estertores. Amostras de sons respiratórios contendo estertores foram normalizadas e reamostradas em 8 kHz. Foram realizados diversos ensaios utilizando a transformada wavelet discreta (DWT) e a análise de discriminante linear (LDA), e avaliados com análise ROC. Um sistema de reconhecimento de padrões foi implementado com DWT, LDA e k-NN para classificar estertores finos, grossos e sons respiratórios normais. O ensaio com diferentes métodos de extensão de borda do sinal durante a decomposição DWT mostrou a influência nos resultados da caracterização. Os resultados indicam que os métodos ZPD, SP0, SYMH, SYMW, ASYMH, PPD e PER são recomendados, enquanto que os métodos SP1 e ASYMW não são recomendados para a decomposição e caracterização de estertores, pois geram características diferentes nas sub-bandas mais altas. Outro ensaio mostrou que a caracterização dos estertores utilizando DWT pode ser feita utilizando-se algumas sub-bandas de decomposição (D3, D4 e D5, no caso de sinais amostrados em 8 kHz), reduzindo-se desta forma o esforço computacional. Outro sistema de classificação implementado utilizando DWT e LDA mostrou que os estertores podem ser classificados indicando a polaridade com elevado grau de acerto (AUC de até 0,9943 para Symlet 19). Dois ensaios foram realizados para seleção da wavelet-mãe que melhor caracterize estertores. O primeiro ensaio avaliou quantitativamente a semelhança entre o estertor e diversas wavelets-mães através do índice de correlação de Pearson. As wavelets-mães que resultaram uma forte correlação com o estertores, se mostrando mais indicadas para serem utilizadas, foram: Reverse Biorthogonal 3.7, Reverse Biorthogonal 5.5, Reverse Biorthogonal 3.5, Daubechies 5, Symlet 5, Daubechies 6, Symlet 7 e Daubechies 7. O segundo ensaio selecionou a wavelet-mãe pela concentração de energia nas sub-bandas. Ensaios anteriores já mostravam que a energia dos estertores decompostos pela DWT se concentra em poucas sub-bandas, então foram selecionadas wavelets-mães que concentrassem maior porcentagem da energia em uma sub-banda específica, que foram: Daubechies 7, Symlet 7, Coiflet 3 e Symlet 12. O último ensaio realizado foi uma combinação de wavelets-mães para melhorar a separabilidade de estertores e sons respiratórios normais. O ensaio mostrou que um sistema de classificação utilizando DWT, LDA e um classificador linear pode separar totalmente as duas classes (índice AUC = 1) quando é utilizada a combinação de wavelets-mães para gerar o vetor de características dos sinais

Signal analysis of spoken consonants

Cílem této práce je nejprve prozkoumat vlastnosti českých souhlásek a problematiku rozpoznávání řeči. Následně vytvořit studii o metodách používaných při automatické souhlásek a potom vytvořit algoritmus na detekce skupin českých souhlásek. Souhlásky se hlavně podílí na srozumitelnosti řeči. Tato práce se zabývá především segmentálním popisem řeči. Prozodické vlastnosti nebudou zatím uvažovány.The aim of this work is at first to explore the characteristics and problems of the Czech consonants and the speech recognition. Then create a study of the methods used in automatic consonants and then create an algorithm to detect groups of the Czech consonants. The consonants are mainly involved in speech intelligibility. This work mainly deals with segmental description of the speech. Prosodic features are not yet considered.